title: Boris Yeltsin

text: During May 1991 Vaclav Havel invited Yeltsin to Prague where the latter unambiguously condemned the Soviet intervention in 1968. On 12 June Yeltsin won 57% of the popular vote in the democratic presidential elections for the Russian republic, defeating Gorbachev's preferred candidate, Nikolai Ryzhkov, who got just 16% of the vote, and four other candidates. In his election campaign, Yeltsin criticized the "dictatorship of the center", but did not suggest the introduction of a market economy. Instead, he said that he would put his head on the railtrack in the event of increased prices. Yeltsin took office on 10 July, and reappointed Ivan Silayev as Chairman of the Council of Ministers of the Russian SFSR. On 18 August 1991, a coup against Gorbachev was launched by the government members opposed to perestroika. Gorbachev was held in Crimea while Yeltsin raced to the White House of Russia (residence of the Supreme Soviet of the RSFSR) in Moscow to defy the coup, making a memorable speech from atop the turret of a tank onto which he had climbed. The White House was surrounded by the military, but the troops defected in the face of mass popular demonstrations. By 21 August most of the coup leaders had fled Moscow and Gorbachev was "rescued" from Crimea and then returned to Moscow. Yeltsin was subsequently hailed by his supporters around the world for rallying mass opposition to the coup.


title: Boris Yeltsin

text: Although restored to his position, Gorbachev had been destroyed politically. Neither union nor Russian power structures heeded his commands as support had swung over to Yeltsin. By September, Gorbachev could no longer influence events outside of Moscow. Taking advantage of the situation, Yeltsin began taking over what remained of the Soviet government, ministry by ministry—including the Kremlin. On 6 November 1991, Yeltsin issued a decree banning all Communist Party activities on Russian soil. In early December 1991, Ukraine voted for independence from the Soviet Union. A week later, on 8 December, Yeltsin met Ukrainian president Leonid Kravchuk and the leader of Belarus, Stanislav Shushkevich, in Belovezhskaya Pushcha. In the Belavezha Accords, the three presidents declared that the Soviet Union no longer existed "as a subject of international law and geopolitical reality," and announced the formation of a voluntary Commonwealth of Independent States (CIS) in its place.


title: Boris Yeltsin

text: According to Gorbachev, Yeltsin kept the plans of the Belovezhskaya meeting in strict secrecy and the main goal of the dissolution of the Soviet Union was to get rid of Gorbachev, who by that time had started to recover his position after the events of August. Gorbachev has also accused Yeltsin of violating the people's will expressed in the referendum in which the majority voted to keep the Soviet Union united. On 12 December, the Supreme Soviet of the RSFSR ratified the Belavezha Accords and denounced the 1922 Union Treaty. It also recalled the Russian deputies from the Council of the Union, leaving that body without a quorum. While this is regarded as the moment that the largest republic of the Soviet Union had seceded, this is not technically the case. Russia appeared to take the line that it was not possible to secede from a country that no longer existed.


title: Boris Yeltsin

text: On 17 December, in a meeting with Yeltsin, Gorbachev accepted the "fait accompli" and agreed to dissolve the Soviet Union. On 24 December, by mutual agreement of the other CIS states (which by this time included all of the remaining republics except Georgia), the Russian Federation took the Soviet Union's seat in the United Nations. The next day, Gorbachev resigned and handed the functions of his office to Yeltsin. On 26 December, the Council of the Republics, the upper house of the Supreme Soviet, voted the Soviet Union out of existence, thereby ending the world's oldest, largest and most powerful Communist state. Economic relations between the former Soviet republics were severely compromised. Millions of ethnic Russians found themselves in the newly formed foreign countries.


title: Boris Yeltsin

text: Initially, Yeltsin promoted the retention of national borders according to the pre-existing Soviet state borders, although this left ethnic Russians as a majority in parts of northern Kazakhstan, eastern Ukraine, and areas of Estonia and Latvia.


title: Boris Yeltsin

text: Just days after the dissolution of the Soviet Union, Yeltsin resolved to embark on a programme of radical economic reform. Improving on Gorbachev's reforms, which sought to expand democracy in the socialist system, the new regime aimed to completely dismantle socialism and fully implement capitalism, converting the world's largest command economy into a free-market one. During early discussions of this transition, Yeltsin's advisers debated issues of speed and sequencing, with an apparent division between those favoring a rapid approach and those favoring a gradual or slower approach. On January 1, 1992, Yeltsin signed accords with U.S. President George H. W. Bush, declaring the Cold War officially over after nearly 47 years. A visit to Moscow from Havel in April 1992 occasioned the written repudiation of the Soviet intervention and the withdrawal of armed forces from Czechoslovakia. Yeltsin laid a wreath during a November 1992 ceremony in Budapest, apologized for the 1956 Soviet intervention in Hungary and handed over to president Árpád Göncz documents from the Communist Party and KGB archives related to the intervention. A treaty of friendship was signed in May 1992 with Lech Wałęsa's Poland, and then another one in August 1992 with Zhelyu Zhelev's Bulgaria.


title: Boris Yeltsin

text: On 2 January 1992, Yeltsin, acting as his own prime minister, ordered the liberalisation of foreign trade, prices, and currency. At the same time, Yeltsin followed a policy of "macroeconomic stabilisation", a harsh austerity regime designed to control inflation. Under Yeltsin's stabilisation programme, interest rates were raised to extremely high levels to tighten money and restrict credit. To bring state spending and revenues into balance, Yeltsin raised new taxes heavily, cut back sharply on government subsidies to industry and construction, and made steep cuts to state welfare spending.


title: Boris Yeltsin

text: In early 1992, prices skyrocketed throughout Russia, and a deep credit crunch shut down many industries and brought about a protracted depression. The reforms devastated the living standards of much of the population, especially the groups dependent on Soviet-era state subsidies and welfare programs. Through the 1990s, Russia's GDP fell by 50%, vast sectors of the economy were wiped out, inequality and unemployment grew dramatically, whilst incomes fell. Hyperinflation, caused by the Central Bank of Russia's loose monetary policy, wiped out many people's personal savings, and tens of millions of Russians were plunged into poverty.


title: Boris Yeltsin

text: Some economists argue that in the 1990s, Russia suffered an economic downturn more severe than the United States or Germany had undergone six decades earlier in the Great Depression. Russian commentators and even some Western economists, such as Marshall Goldman, widely blamed Yeltsin's economic programme for the country's disastrous economic performance in the 1990s. Many politicians began to quickly distance themselves from the programme. In February 1992, Russia's vice president, Alexander Rutskoy denounced the Yeltsin programme as "economic genocide." By 1993, conflict over the reform direction escalated between Yeltsin on the one side, and the opposition to radical economic reform in Russia's parliament on the other.


title: Boris Yeltsin

text: Throughout 1992 Yeltsin wrestled with the Supreme Soviet of Russia and the Congress of People's Deputies for control over government, government policy, government banking and property. In the course of 1992, the speaker of the Russian Supreme Soviet, Ruslan Khasbulatov, came out in opposition to the reforms, despite claiming to support Yeltsin's overall goals. In December 1992, the 7th Congress of People's Deputies succeeded in turning down the Yeltsin-backed candidacy of Yegor Gaidar for the position of Russian Prime Minister. An agreement was brokered by Valery Zorkin, chairman of the Constitutional Court, which included the following provisions: a national referendum on the new constitution; parliament and Yeltsin would choose a new head of government, to be confirmed by the Supreme Soviet; and the parliament was to cease making constitutional amendments that change the balance of power between the legislative and executive branches. Eventually, on 14 December, Viktor Chernomyrdin, widely seen as a compromise figure, was confirmed in the office.


title: Boris Yeltsin

text: The conflict escalated soon, however, with the parliament changing its prior decision to hold a referendum. Yeltsin, in turn, announced in a televised address to the nation on 20 March 1993, that he was going to assume certain "special powers" in order to implement his programme of reforms. In response, the hastily called 9th Congress of People's Deputies attempted to remove Yeltsin from presidency through impeachment on 26 March 1993. Yeltsin's opponents gathered more than 600 votes for impeachment, but fell 72 votes short of the required two-thirds majority.


title: Boris Yeltsin

text: During the summer of 1993, a situation of dual power developed in Russia. From July, two separate administrations of the Chelyabinsk Oblast functioned side by side, after Yeltsin refused to accept the newly elected pro-parliament head of the region. The Supreme Soviet pursued its own foreign policies, passing a declaration on the status of Sevastopol. In August, a commentator reflected on the situation as follows: "The President issues decrees as if there were no Supreme Soviet, and the Supreme Soviet suspends decrees as if there were no President." (Izvestia, 13 August 1993).


title: Boris Yeltsin

text: On 21 September 1993, in breach of the constitution, Yeltsin announced in a televised address his decision to disband the Supreme Soviet and Congress of People's Deputies by decree. In his address, Yeltsin declared his intent to rule by decree until the election of the new parliament and a referendum on a new constitution, triggering the constitutional crisis of October 1993. On the night after Yeltsin's televised address, the Supreme Soviet declared Yeltsin removed from the presidency for breaching the constitution, and Vice-President Alexander Rutskoy was sworn in as acting president.


title: Boris Yeltsin

text: Between 21 and 24 September, Yeltsin was confronted by popular unrest. Demonstrators protested the terrible living conditions under Yeltsin. Since 1989, GDP had declined by half. Corruption was rampant, violent crime was skyrocketing, medical services were collapsing, food and fuel were increasingly scarce and life expectancy was falling for all but a tiny handful of the population; moreover, Yeltsin was increasingly getting the blame. By early-October, Yeltsin had secured the support of Russia's army and ministry of interior forces. In a massive show of force, Yeltsin called up tanks to shell the Russian White House (parliament building). The attack killed 187 people and wounded almost 500 others.


title: Boris Yeltsin

text: As the Supreme Soviet was dissolved, elections to the newly established parliament, the State Duma, were held in December 1993. Candidates associated with Yeltsin's economic policies were overwhelmed by a huge anti-Yeltsin vote, the bulk of which was divided between the Communist Party and ultra-nationalists. However, the referendum held at the same time approved the new constitution, which significantly expanded the powers of the president, giving Yeltsin the right to appoint the members of the government, to dismiss the prime minister and, in some cases, to dissolve the Duma.


title: Boris Yeltsin

text: The US Department of State seemed to confuse Yeltsin over German re-unification and dismemberment of the Helsinki Final Act and ensuing Partnership for Peace (PfP) push for NATO expansion. There is some question as to the involvement of his Minister of Foreign Affairs Andrei Kozyrev, who in August 1993 was painted by Lech Wałęsa (after his failed attempt to hoodwink Yeltsin by one-on-one subterfuge) as a saboteur of Polish aspirations for NATO membership but was regarded by domestic opponents as suborned by Uncle Sam. In Yeltsin’s letter to Bill Clinton dated 15 September 1993 he strongly favours "a pan-European security system" instead of NATO and warns:


title: Boris Yeltsin

text: After his August visit to Warsaw, Yeltsin saw the explosion of fright over NATO in the old guard and thereafter the window of détente slammed shut. By December 1994, the month in which was signed the Budapest Memorandum, Clinton began to understand that Russia had concluded that he was "subordinating, if not abandoning, integration [of Russia] to NATO expansion." In July 1995 by which time the Russians had signed up to PfP, Yeltsin said to Clinton "we must stick to our position, which is that there should be no rapid expansion of NATO.. it’s important that the OSCE be the principal mechanism for developing a new security order in Europe. NATO is a factor, too, of course, but NATO should evolve into a political[-only] organization."


title: Boris Yeltsin

text: In December 1994, Yeltsin ordered the military invasion of Chechnya in an attempt to restore Moscow's control over the republic. Nearly two years later, Yeltsin withdrew federal forces from the devastated Chechnya under a 1996 peace agreement brokered by Alexander Lebed, Yeltsin's then-security chief. The peace deal allowed Chechnya greater autonomy but not full independence. The decision to launch the war in Chechnya dismayed many in the West. "Time" magazine wrote:


title: Boris Yeltsin

text: Then, what was to be made of Boris Yeltsin? Clearly he could no longer be regarded as the democratic hero of Western myth. But had he become an old-style communist boss, turning his back on the democratic reformers he once championed and throwing in his lot with militarists and ultranationalists? Or was he a befuddled, out-of-touch chief being manipulated, knowingly or unwittingly, by—well, by whom exactly? If there was to be a dictatorial coup, would Yeltsin be its victim or its leader?


title: Boris Yeltsin

text: In 1995, a Black Brant sounding rocket launched from the Andøya Space Center caused a high alert in Russia, known as the Norwegian rocket incident. The Russians were alerted that it might be a nuclear missile launched from an American submarine. The incident occurred in the post-Cold War era, where many Russians were still very suspicious of the United States and NATO. A full alert was passed up through the military chain of command all the way to Yeltsin, who was notified and the "nuclear briefcase" (known in Russia as "Cheget") used to authorize nuclear launch was automatically activated. Russian satellites indicated that no massive attack was underway and he agreed with advisors that it was a false alarm.


title: Boris Yeltsin

text: Following the dissolution of the Soviet Union, Yeltsin promoted privatization as a way of spreading ownership of shares in former state enterprises as widely as possible to create political support for his economic reforms. In the West, privatization was viewed as the key to the transition from Communism in Eastern Europe, ensuring a quick dismantling of the Soviet-era command economy to make way for "free market reforms". In the early-1990s, Anatoly Chubais, Yeltsin's deputy for economic policy, emerged as a leading advocate of privatization in Russia.


title: Boris Yeltsin

text: In late 1992, Yeltsin launched a programme of free vouchers as a way to give mass privatization a jump-start. Under the programme, all Russian citizens were issued vouchers, each with a nominal value of around 10,000 rubles, for the purchase of shares of select state enterprises. Although each citizen initially received a voucher of equal face value, within months the majority of them converged in the hands of intermediaries who were ready to buy them for cash right away.


title: Boris Yeltsin

text: In 1995, as Yeltsin struggled to finance Russia's growing foreign debt and gain support from the Russian business elite for his bid in the 1996 presidential elections, the Russian president prepared for a new wave of privatization offering stock shares in some of Russia's most valuable state enterprises in exchange for bank loans. The programme was promoted as a way of simultaneously speeding up privatization and ensuring the government a cash infusion to cover its operating needs.'


title: Boris Yeltsin

text: However, the deals were effectively giveaways of valuable state assets to a small group of tycoons in finance, industry, energy, telecommunications, and the media who came to be known as "oligarchs" in the mid-1990s. This was due to the fact that ordinary people sold their vouchers for cash. The vouchers were bought by a small group of investors. By mid-1996, substantial ownership shares over major firms were acquired at very low prices by a handful of people. Boris Berezovsky, who controlled major stakes in several banks and the national media, emerged as one of Yeltsin's most prominent supporters. Along with Berezovsky, Mikhail Khodorkovsky, Vladimir Potanin, Vladimir Bogdanov, Rem Viakhirev, Vagit Alekperov, Alexander Smolensky, Viktor Vekselberg, Mikhail Fridman and a few years later Roman Abramovich, were habitually mentioned in the media as Russia's oligarchs.


title: Boris Yeltsin

text: On 5 December 1991, Senator Jesse Helms, ranking member of the Minority on the U.S. Senate Committee on Foreign Relations, wrote to Yeltsin concerning U.S. servicemen who were POWs or MIAs: "The status of thousands and thousands of American servicemen who are held by Soviet and other Communist forces, and who were never repatriated after every major war this century, is of grave concern to the American people."


title: Boris Yeltsin

text: Yeltsin responded with a statement made on 15 June 1992, whilst being interviewed on board his presidential jet en route to the United States, "Our archives have shown that it is true — some of them were transferred to the territory of the USSR and were kept in labour camps... We can only surmise that some of them may still be alive." On 10 December 1991, five days after Helms had written to Yeltsin regarding American servicemen, he again wrote to Yeltsin, this time concerning Korean Air Lines Flight 007 (KAL 007) requesting information concerning possible survivors, including Georgia Congressman Larry McDonald, and their whereabouts.


title: Boris Yeltsin

text: In March 1992, Yeltsin handed over KAL 007's black box without its tapes to South Korean President Roh Tae-woo at the end of the plenary session of the South Korean National Assembly, saying "We apologize for the tragedy and are trying to settle some unsolved issues." Yeltsin released the tapes of the KAL 007's black box (its digital flight data recorder and cockpit voice recorder) to the International Civil Aviation Organization (ICAO) on 8 January 1993. For years the Soviet authorities had denied possessing these tapes. The openness of Yeltsin about POW/MIA and KAL 007 matters may also have signalled his willingness for more openness to the West. In 1992, which he labelled the "window of opportunity", he was willing to discuss biological weapons with the United States and admitted that the Sverdlovsk anthrax leak of 2 April 1979 (which Yeltsin had originally been involved in concealing) had been caused as the result of a mishap at a military facility. The Russian government had maintained that the cause was contaminated meat. The true number of victims in the anthrax outbreak at Sverdlovsk, about east of Moscow, is unknown.


title: Boris Yeltsin

text: In February 1996, Yeltsin announced that he would seek a second term in the 1996 Russian presidential election in the summer. The announcement followed weeks of speculation that Yeltsin was at the end of his political career because of his health problems and growing unpopularity in Russia. At the time, Yeltsin was recuperating from a series of heart attacks. Domestic and international observers also noted his occasionally erratic behavior. When campaigning began in early 1996, Yeltsin's popularity was close to being non-existent. Meanwhile, the opposition Communist Party had already gained ground in parliamentary voting on 17 December 1995, and its candidate, Gennady Zyuganov, had a strong grassroots organization, especially in the rural areas and small towns, and appealed effectively to memories of the old days of Soviet prestige on the international stage and the domestic order under state socialism.


title: Boris Yeltsin

text: Panic struck the Yeltsin team when opinion polls suggested that the ailing president could not win; some members of his entourage urged him to cancel the presidential elections and effectively rule as a dictator from then on. Instead, Yeltsin changed his campaign team, assigning a key role to his daughter, Tatyana Dyachenko, and appointing Chubais as campaign manager. Chubais, acting as both Yeltsin's campaign manager and adviser on Russia's privatization programme, used his control of the privatization programme as an instrument of Yeltsin's re-election campaign.


title: Boris Yeltsin

text: In mid-1996, Chubais and Yeltsin recruited a team of a handful of financial and media oligarchs to bankroll the Yeltsin campaign and guarantee favorable media coverage to the president on national television and in leading newspapers. In return, Chubais allowed well-connected Russian business leaders to acquire majority stakes in some of Russia's most valuable state-owned assets. Led by the efforts of Mikhail Lesin, the media painted a picture of a fateful choice for Russia, between Yeltsin and a "return to totalitarianism." The oligarchs even played up the threat of civil war if a Communist was elected president.


title: Boris Yeltsin

text: The American president, Bill Clinton, also committed himself to the campaign. American advisors were sent, on instruction from the White House, to join the campaign team of the sitting Russian president to teach new electoral techniques. Several European governments also showed their support for Yeltsin. French Prime Minister Alain Juppé visited Moscow on February 14, the day Yeltsin's candidacy was announced, and said he hoped the election campaign would be "an opportunity to highlight the achievements of President Yeltsin's reform policy." On the same day, German Chancellor Helmut Kohl visited Moscow, where he presented Yeltsin as "an absolutely reliable partner who has always respected his commitments."


title: Boris Yeltsin

text: Yeltsin campaigned energetically, dispelling concerns about his health, and maintained a high media profile. To boost his popularity, Yeltsin promised to abandon some of his more unpopular economic reforms, boost welfare spending, end the war in Chechnya, and pay wage and pension arrears. Yeltsin had benefited from the approval of a US$10.2 billion International Monetary Fund loan to Russia, which helped to keep his government afloat.


title: Boris Yeltsin

text: Zyuganov, who lacked Yeltsin's resources and financial backing, saw his strong initial lead whittled away. After the first round on 16 June, Yeltsin appointed a highly popular candidate Alexander Lebed, who finished in third place in the first round, secretary of the Security Council of Russia, sacked at the latter's behest defence minister Pavel Grachev, and on 20 June sacked a number of his "siloviki", one of them being his chief of presidential security Alexander Korzhakov, viewed by many as Yeltsin's éminence grise. In the run-off on 3 July, with a turnout of 68.9%, Yeltsin won 53.8% of the vote and Zyuganov 40.7%, with the rest (5.9%) voting "against all".


title: Boris Yeltsin

text: Yeltsin underwent emergency quintuple heart bypass surgery in November 1996, and remained in the hospital for months. During his presidency, Russia received US$40 billion in funds from the International Monetary Fund and other international lending organisations. However, his opponents allege that most of these funds were stolen by people from Yeltsin's circle and placed into foreign banks.


title: Boris Yeltsin

text: In 1998, a political and economic crisis emerged when Yeltsin's government defaulted on its debts, causing financial markets to panic and the rouble to collapse in the 1998 Russian financial crisis. During the 1999 Kosovo War, Yeltsin strongly opposed the NATO military campaign against Yugoslavia, and warned of possible Russian intervention if NATO deployed ground troops to Kosovo. In televised comments he stated: "I told NATO, the Americans, the Germans: Don't push us towards military action. Otherwise there will be a European war for sure and possibly a world war." Yeltsin said that NATO’s bombing of Yugoslavia "trampled upon the foundations of international law and the United Nations charter."


title: Boris Yeltsin

text: On 9 August 1999, Yeltsin fired his Prime Minister, Sergei Stepashin, and for the fourth time, fired his entire Cabinet. In Stepashin's place, he appointed Vladimir Putin, relatively unknown at that time, and announced his wish to see Putin as his successor. In late 1999, Yeltsin and U.S. President Bill Clinton openly disagreed on the war in Chechnya. At the November meeting of the Organization for Security and Cooperation in Europe, Clinton pointed his finger at Yeltsin and demanded he halt bombing attacks that had resulted in many civilian casualties. Yeltsin immediately left the conference.


title: Boris Yeltsin

text: In December, whilst visiting China to seek support on Chechnya, Yeltsin replied to Clinton's criticism of a Russian ultimatum to citizens of Grozny. He bluntly pronounced: "Yesterday, Clinton permitted himself to put pressure on Russia. It seems he has for a minute, for a second, for half a minute, forgotten that Russia has a full arsenal of nuclear weapons. He has forgotten about that." Clinton dismissed Yeltsin's comments stating: "I didn't think he'd forgotten that America was a great power when he disagreed with what I did in Kosovo." It fell to Putin to downplay Yeltsin's comments and present reassurances about U.S. and Russian relations.


title: Boris Yeltsin

text: On 15 May 1999, Yeltsin survived another attempt of impeachment, this time by the democratic and communist opposition in the State Duma. He was charged with several unconstitutional activities, including the signing of the Belovezha Accords dissolving the Soviet Union in December 1991, the coup-d'état in October 1993, and initiating the war in Chechnya in 1994. None of these charges received the two-thirds majority of the Duma required to initiate the process of impeachment of the president.


title: Boris Yeltsin

text: With Pavel Borodin as the Kremlin property manager, Swiss construction firm Mabetex was awarded many important Russian government contracts. They were awarded the contracts to reconstruct, renovate and refurbish the former Russian Federation Parliament, the Russian Opera House, State Duma and the Moscow Kremlin.


title: Boris Yeltsin

text: In 1998, the Prosecutor General of Russia, Yuri Skuratov, opened a bribery investigation against Mabetex, accusing its Chief Executive Officer Behgjet Pacolli of bribing Yeltsin and his family. Swiss authorities issued an international arrest warrant for Pavel Borodin, the official who managed the Kremlin's property empire. Stating that bribery was a common business practice in Russia, Pacolli confirmed in early December 1999 that he had guaranteed five credit cards for Yeltsin's wife, Naina, and two daughters, Tatyana and Yelena. Yeltsin resigned a few weeks later on 31 December 1999, appointing Vladimir Putin as his successor. Putin's first decree as president was lifelong immunity from prosecution for Yeltsin.


title: Boris Yeltsin

text: On 31 December 1999, Yeltsin issued a televised resignation speech. In it, he praised the advances in cultural, political, and economic freedom that his administration had overseen although apologised to Russia's people for "not making many of your and my dreams come true. What seemed simple to do proved to be excruciatingly difficult."


title: Boris Yeltsin

text: By some estimates, his approval ratings when leaving office were as low as 2%. Polling also suggests that a majority of the Russian population were pleased by Yeltsin's resignation.


title: Boris Yeltsin

text: Yeltsin suffered from heart disease during his first term as President of the Russian Federation, probably continuing for the rest of his life. He is known to have suffered heart problems in March 1990, just after being elected as a member of parliament. It was common knowledge that, in early 1996, he was recuperating from a series of heart attacks and, soon after, he spent months in hospital recovering from a quintuple bypass operation (see above).


title: Boris Yeltsin

text: According to numerous reports, Yeltsin was alcohol dependent until 1996, when his worsening health made him give up heavy drinking. The topic made headlines abroad during Yeltsin's visit to the U.S. in 1989 for a series of lectures on social and political life in the Soviet Union. A report in the Italian newspaper "La Repubblica", reprinted by "Pravda", reported that Yeltsin often appeared drunk in public. His alcoholism was also the subject of media discussion following his meeting with U.S. Deputy Secretary of State Strobe Talbott following Clinton's inauguration in 1993 and an incident during a flight stop-over at Shannon Airport, Ireland, in September 1994, when the waiting Irish prime minister, Albert Reynolds, was told that Yeltsin was unwell and would not be leaving the aircraft. Reynolds tried to make excuses for him in an effort to offset his own humiliation in waiting in vain outside the plane to meet him. Speaking to the media in March 2010, Yeltsin's daughter, Tatyana Yumasheva, claimed that her father had suffered a heart attack on the flight from the United States to Moscow and was therefore not in a position to leave the plane.


title: Boris Yeltsin

text: According to former deputy prime minister of Russia Boris Nemtsov, the bizarre behavior of Yeltsin resulted from "strong drugs" given to him by Kremlin doctors, which were incompatible even with a small amount of alcohol. This was discussed by journalist Yelena Tregubova from the "Kremlin pool" in connection with an episode during Yeltsin's visit to Stockholm in 1997, when Yeltsin suddenly started talking nonsense (he allegedly told his bemused audience that Swedish meatballs reminded him of Björn Borg's face), lost his balance, and almost fell down on the podium after drinking a single glass of champagne.


title: Boris Yeltsin

text: In his memoirs, Yeltsin claimed no recollection of the event but did make a passing reference to the incident when he met Borg a year later at the World Circle Kabaddi Cup in Hamilton, Ontario, where the pair had been invited to present the trophy. He made a hasty withdrawal from the funeral of King Hussein of Jordan in February 1999 to use the facilities.


title: Boris Yeltsin

text: After Yeltsin's death, Michiel Staal, a Dutch neurosurgeon, said that his team had been secretly flown to Moscow to operate on Yeltsin in 1999. Yeltsin suffered from an unspecified neurological disorder that affected his sense of balance, causing him to wobble as if in a drunken state; the goal of the operation was to reduce the pain.


title: Boris Yeltsin

text: Bill Clinton claimed that on a 1995 visit to Washington, Yeltsin was found on Pennsylvania Avenue, drunk, in his underwear and trying to hail a taxi cab in order to find pizza.


title: Boris Yeltsin

text: Yeltsin's personal and health problems received a great deal of attention in the global press. As the years went on, he was often viewed as an increasingly drunk and unstable leader, rather than the inspiring figure he was once seen as. The possibility that he might die in office was often discussed. Starting in the last years of his presidential term, Yeltsin's primary residence was the "Gorki-9" presidential dacha west of Moscow. He made frequent stays at the nearby government sanatorium in Barvikha. In October 1999, Yeltsin was hospitalized with flu and a fever, and in the following month, he was hospitalized with pneumonia, just days after receiving treatment for bronchitis.


title: Boris Yeltsin

text: Yeltsin maintained a low profile after his resignation, making almost no public statements or appearances. He criticized his successor Putin in December 2000 for supporting the reintroduction of the tune of the Soviet-era national anthem. In January 2001 he was hospitalized for six weeks with pneumonia resulting from a viral infection. On 13 September 2004, following the Beslan school hostage crisis and nearly concurrent terrorist attacks in Moscow, Putin launched an initiative to replace the election of regional governors with a system whereby they would be directly appointed by the president and approved by regional legislatures. Yeltsin, together with Mikhail Gorbachev, publicly criticized Putin's plan as a step away from democracy in Russia and a return to the centrally-run political apparatus of the Soviet era.


title: Boris Yeltsin

text: In September 2005, Yeltsin underwent a hip operation in Moscow after breaking his femur in a fall while on holiday in the Italian island of Sardinia. On 1 February 2006, Yeltsin celebrated his 75th birthday.


title: Boris Yeltsin

text: Yeltsin died of congestive heart failure on 23 April 2007, aged 76. According to experts quoted by "Komsomolskaya Pravda", the onset of Yeltsin's condition began during his visit to Jordan between 25 March and 2 April. He was buried in the Novodevichy Cemetery on 25 April 2007, following a period during which his body had lain in repose in the Cathedral of Christ the Saviour in Moscow.


title: Boris Yeltsin

text: Yeltsin was the first Russian head of state in 113 years to be buried in a church ceremony, after Emperor Alexander III. He was survived by his wife, Naina Iosifovna Yeltsina, whom he married in 1956, and their two daughters Yelena and Tatyana, born in 1957 and 1960, respectively.


title: Boris Yeltsin

text: President Putin declared the day of his funeral a national day of mourning, with the nation's flags flown at half-staff and all entertainment programs suspended for the day. Putin said, upon declaring 25 April 2007 a day of national mourning, that:


title: Boris Yeltsin

text: During the late Soviet period, Yeltsin's ideological worldview began to shift. Colton argued that populism and "a non-ethnic Russianism" had begun to enter Yeltsin's thinking while he was First Secretary of Sverdlovsk. In the late 1980s, Yeltsin told the Athens daily newspaper "Kathimerini" that "I regard myself as a social democrat", adding: "Those who still believe in communism are moving in the sphere of fantasy."


title: Boris Yeltsin

text: Linking Yeltsin with "liberal Russian nationalism", Alfred B. Evans described Yeltsin as having "exerted a crucial influence on the development of Russian nationalism." Yeltsin helped to channel the aspirations of Russian nationalism in ways that did not lead to clashes with the nationalisms of other national groups within the Soviet Union. As head of the Russian SFSR, he stressed the specific interests of the Russian republic within the broader Soviet Union. Evans compared Yeltsin's turn away from the "empire-building" of the Soviet Union to the ideas of the writer and dissident Aleksandr Solzhenitsyn, who had called in the 1980s for Russia to extricate itself from the Soviet Union. However, Evans thought that Yeltsin still appeared to believe by 1990 that the Ukrainians and Belarusians, as fellow East Slavic nationalities, would want to remain politically united with Russia in federal form. By 1991, it was obvious that this would not occur as the Ukrainian population favored full independence. Over the course of his presidency, he made increasing concessions to right-wing ethnic Russian nationalism by expressing growing concern over the fate of ethnic Russians in neighboring countries.


title: Boris Yeltsin

text: Colton described Yeltsin as a man who "teemed with inner complexities", who exhibited both a "mathematical cast of mind" and a "taste for adventure", noting that Yeltsin had "the intuition for grasping a situation holistically". Colton thought Yeltsin could be bullheaded, and restless. Evans noted that in Yeltsin's autobiography, the leader appeared to view himself as more of a Soviet person than a Russian. Throughout his life, Yeltsin sustained a number of health problems which he would usually try to conceal. As a child, he sustained both a broken nose and a maimed hand, physical attributes he remained self-conscious about; in public he would often conceal his left hand under the table or behind his tie. He was also deaf on the right side due to a middle-ear infection. Although his mother was a devout Orthodox Christian, Yeltsin did not grow up as a practitioner, only becoming so in the 1980s and 1990s.


title: Boris Yeltsin

text: Yeltsin stated that his "style of management" was "tough" and that he "demanded strict discipline and fulfilment of promises". Yeltsin was a workaholic; at UPI university, he developed the habit of sleeping for only four hours at night. He was punctual and very strict regarding the tardiness of his subordinates. He had an excellent memory, and enjoyed reading; by 1985 his family had around 6000 volumes in their possession. At UPI university, he was known for enjoying practical jokes. He enjoyed listening to folk songs and pop tunes, and from youth could play the "lozhki" spoons. Until poor health stopped him in the 1990s, Yeltsin enjoyed swimming in icy water, and throughout his life started each day with a cold shower. He also loved using the "banya" steambath. Yeltsin also enjoyed hunting and had his own collection of hunting guns. He liked to give watches and other keepsakes to his employees, often as a means of motivating them to work harder. He disliked people swearing, and when frustrated or angry, he was known to often snap pencils in his hand.


title: Boris Yeltsin

text: Yeltsin had a high tolerance for alcohol, and by the 1980s he was drinking alcohol at or above the average for the party elite. Yeltsin's favorite writer was Anton Chekhov, although he also enjoyed the work of Sergei Yesenin and Alexander Pushkin. Colton described Yeltsin as having a "husky baritone" voice.


title: Boris Yeltsin

text: Doder and Branson noted that Yeltsin was "a hero for young Russians, a cult figure to those who were not necessarily anticommunists but who were filled with bitterness and apathy" from the Brezhnev years. They noted he was "ebullient, almost outrageously open", and also "charismatic". They added that Yeltsin presented himself as "a true working-class hero" when challenging the Soviet administration.


title: Boris Yeltsin

text: Yelena briefly married a school friend, Aleksei Fefelov, against her parents' wishes. They had a daughter, Yekaterina, in 1979, before separating. Yelena then married an Aeroflot pilot, Valerii Okulov, with whom she had a second daughter, Mariya, in 1983. Yeltsin's other daughter, Tatyana, married fellow student Vilen Khairullin, an ethnic Tatar, while studying at Moscow State University in 1980. In 1981 they had a son, named Boris after his grandfather, but soon separated. Tatyana then married again, to Leonid Dyachenko, and for a while they lived with Yeltsin at his Moscow apartment during the mid-1980s. Yeltsin was loyal to his friends. As friends, Yeltsin selected individuals he deemed to be professionally competent and morally fastidious. Aron noted that Yeltsin could be "an inexhaustible fount of merriment, exuberance and hospitality" among his friends.


title: Boris Yeltsin

text: Evaluations of Yeltsin range from highly positive to highly negative, with not much in the middle. Former United States Ambassador to Russia Michael McFaul emphasizes the range pro and con:


title: Boris Yeltsin

text: Colton suggested that "Yeltsin leaves nobody indifferent. He needs to be understood if we are to understand the age we inhabit". Aron characterised him as "Russia's first modern leader". Colton understood him as "a hero in history", albeit one who was "enigmatic and flawed". He expressed the view that Yeltsin was part of "the global trend away from authoritarianism and statism" that occurred in the 1990s, comparing him to Nelson Mandela, Lech Wałęsa, Václav Havel and Mikhail Gorbachev.


title: Boris Yeltsin

text: In the years following his presidency, there was comparatively little interest among biographers and historians in researching Yeltsin's life.


title: Boris Yeltsin

text: During his career as a figure in the Soviet Union, Yeltsin received ten medals and awards for his service to the state. In April 2008, a new memorial to Yeltsin was dedicated in Moscow's Novodevichy cemetery, to mixed reactions. At the memorial service, a military chorus performed Russia's national anthem – an anthem that was changed shortly after the end of Yeltsin's term, to follow the music of the old Soviet anthem, with lyrics reflecting Russia's new status.


title: Boris Yeltsin

text: Ryabov, who was formerly a close ally of Yeltsin's, claimed that his actions in the 1990s revealed that he was a turncoat.


title: Boris Yeltsin

text: In 2013, a memorial sculpture in relief, dedicated to Yeltsin, was erected on Nunne street, at the base of the Patkuli stairs in Tallinn, for his contribution to the peaceful independence of Estonia during 1990–1991.


title: Bird

text: Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton. Birds live worldwide and range in size from the bee hummingbird to the ostrich. There are about ten thousand living species, more than half of which are passerine, or "perching" birds. Birds have whose development varies according to species; the only known groups without wings are the extinct moa and elephant birds. Wings, which are modified forelimbs, gave birds the ability to fly, although further evolution has led to the loss of flight in some birds, including ratites, penguins, and diverse endemic island species. The digestive and respiratory systems of birds are also uniquely adapted for flight. Some bird species of aquatic environments, particularly seabirds and some waterbirds, have further evolved for swimming.


title: Bird

text: Birds are feathered theropod dinosaurs and constitute the only known living dinosaurs. Likewise, birds are considered reptiles in the modern cladistic sense of the term, and their closest living relatives are the crocodilians. Birds are descendants of the primitive avialans (whose members include "Archaeopteryx") which first appeared about 160 million years ago (mya) in China. According to DNA evidence, modern birds (Neornithes) evolved in the Middle to Late Cretaceous, and diversified dramatically around the time of the Cretaceous–Paleogene extinction event 66 mya, which killed off the pterosaurs and all non-avian dinosaurs.


title: Bird

text: Many social species pass on knowledge across generations, which is considered a form of culture. Birds are social, communicating with visual signals, calls, and songs, and participating in such behaviours as cooperative breeding and hunting, flocking, and mobbing of predators. The vast majority of bird species are socially (but not necessarily sexually) monogamous, usually for one breeding season at a time, sometimes for years, and rarely for life. Other species have breeding systems that are polygynous (one male with many females) or, rarely, polyandrous (one female with many males). Birds produce offspring by laying eggs which are fertilised through sexual reproduction. They are usually laid in a nest and incubated by the parents. Most birds have an extended period of parental care after hatching.


title: Bird

text: Many species of birds are economically important as food for human consumption and raw material in manufacturing, with domesticated and undomesticated birds being important sources of eggs, meat, and feathers. Songbirds, parrots, and other species are popular as pets. Guano (bird excrement) is harvested for use as a fertiliser. Birds figure throughout human culture. About 120 to 130 species have become extinct due to human activity since the 17th century, and hundreds more before then. Human activity threatens about 1,200 bird species with extinction, though efforts are underway to protect them. Recreational birdwatching is an important part of the ecotourism industry.


title: Bird

text: The first classification of birds was developed by Francis Willughby and John Ray in their 1676 volume "Ornithologiae".


title: Bird

text: Carl Linnaeus modified that work in 1758 to devise the taxonomic classification system currently in use. Birds are categorised as the biological class Aves in Linnaean taxonomy. Phylogenetic taxonomy places Aves in the clade Theropoda.


title: Bird

text: Aves and a sister group, the order Crocodilia, contain the only living representatives of the reptile clade Archosauria. During the late 1990s, Aves was most commonly defined phylogenetically as all descendants of the most recent common ancestor of modern birds and "Archaeopteryx lithographica". However, an earlier definition proposed by Jacques Gauthier gained wide currency in the 21st century, and is used by many scientists including adherents to the "PhyloCode". Gauthier defined Aves to include only the crown group of the set of modern birds. This was done by excluding most groups known only from fossils, and assigning them, instead, to the broader group Avialae, in part to avoid the uncertainties about the placement of "Archaeopteryx" in relation to animals traditionally thought of as theropod dinosaurs.


title: Bird

text: Gauthier and de Queiroz identified four different definitions for the same biological name "Aves", which is a problem. The authors proposed to reserve the term Aves only for the crown group consisting of the last common ancestor of all living birds and all of its descendants, which corresponds to meaning number 4 below. He assigned other names to the other groups.


title: Bird

text: Under the fourth definition "Archaeopteryx", traditionally considered one of the earliest members of Aves, is removed from this group, becoming a non-avian dinosaur instead. These proposals have been adopted by many researchers in the field of palaeontology and bird evolution, though the exact definitions applied have been inconsistent. Avialae, initially proposed to replace the traditional fossil content of Aves, is often used synonymously with the vernacular term "bird" by these researchers.


title: Bird

text: Most researchers define Avialae as branch-based clade, though definitions vary. Many authors have used a definition similar to "all theropods closer to birds than to "Deinonychus"", with "Troodon" being sometimes added as a second external specifier in case it is closer to birds than to "Deinonychus". Avialae is also occasionally defined as an apomorphy-based clade (that is, one based on physical characteristics). Jacques Gauthier, who named Avialae in 1986, re-defined it in 2001 as all dinosaurs that possessed feathered wings used in flapping flight, and the birds that descended from them.


title: Bird

text: Despite being currently one of the most widely used, the crown-group definition of Aves has been criticised by some researchers. Lee and Spencer (1997) argued that, contrary to what Gauthier defended, this definition would not increase the stability of the clade and the exact content of Aves will always be uncertain because any defined clade (either crown or not) will have few synapomorphies distinguishing it from its closest relatives. Their alternative definition is synonymous to Avifilopluma.


title: Bird

text: Based on fossil and biological evidence, most scientists accept that birds are a specialised subgroup of theropod dinosaurs and, more specifically, members of Maniraptora, a group of theropods which includes dromaeosaurids and oviraptorosaurs, among others. As scientists have discovered more theropods closely related to birds, the previously clear distinction between non-birds and birds has become blurred. Recent discoveries in the Liaoning Province of northeast China, which demonstrate many small theropod feathered dinosaurs, contribute to this ambiguity.


title: Bird

text: The consensus view in contemporary palaeontology is that the flying theropods, or avialans, are the closest relatives of the deinonychosaurs, which include dromaeosaurids and troodontids. Together, these form a group called Paraves. Some basal members of Deinonychosauria, such as "Microraptor", have features which may have enabled them to glide or fly. The most basal deinonychosaurs were very small. This evidence raises the possibility that the ancestor of all paravians may have been arboreal, have been able to glide, or both. Unlike "Archaeopteryx" and the non-avialan feathered dinosaurs, who primarily ate meat, recent studies suggest that the first avialans were omnivores.


title: Bird

text: The Late Jurassic "Archaeopteryx" is well known as one of the first transitional fossils to be found, and it provided support for the theory of evolution in the late 19th century. "Archaeopteryx" was the first fossil to display both clearly traditional reptilian characteristics—teeth, clawed fingers, and a long, lizard-like tail—as well as wings with flight feathers similar to those of modern birds. It is not considered a direct ancestor of birds, though it is possibly closely related to the true ancestor.


title: Bird

text: Over 40% of key traits found in modern birds evolved during the 60 million year transition from the earliest bird-line archosaurs to the first maniraptoromorphs, i.e. the first dinosaurs closer to living birds than to "Tyrannosaurus rex". The loss of osteoderms otherwise common in archosaurs and acquisition of primitive feathers might have occurred early during this phase. After the appearance of Maniraptoromorpha, the next 40 million years marked a continuous reduction of body size and the accumulation of neotenic (juvenile-like) characteristics. Hypercarnivory became increasingly less common while braincases enlarged and forelimbs became longer. The integument evolved into complex, pennaceous feathers.


title: Bird

text: The oldest known paravian (and probably the earliest avialan) fossils come from the Tiaojishan Formation of China, which has been dated to the late Jurassic period (Oxfordian stage), about 160 million years ago. The avialan species from this time period include "Anchiornis huxleyi", "Xiaotingia zhengi", and "Aurornis xui".


title: Bird

text: The well-known probable early avialan, "Archaeopteryx", dates from slightly later Jurassic rocks (about 155 million years old) from Germany. Many of these early avialans shared unusual anatomical features that may be ancestral to modern birds but were later lost during bird evolution. These features include enlarged claws on the second toe which may have been held clear of the ground in life, and long feathers or "hind wings" covering the hind limbs and feet, which may have been used in aerial manoeuvreing.


title: Bird

text: Avialans diversified into a wide variety of forms during the Cretaceous period. Many groups retained primitive characteristics, such as clawed wings and teeth, though the latter were lost independently in a number of avialan groups, including modern birds (Aves). Increasingly stiff tails (especially the outermost half) can be seen in the evolution of maniraptoromorphs, and this process culminated in the appearance of the pygostyle, an ossification of fused tail vertebrae. In the late Cretaceous, about 100 million years ago, the ancestors of all modern birds evolved a more open pelvis, allowing them to lay larger eggs compared to body size. Around 95 million years ago, they evolved a better sense of smell.


title: Bird

text: A third stage of bird evolution starting with Ornithothoraces (the "bird-chested" avialans) can be associated with the refining of aerodynamics and flight capabilities, and the loss or co-ossification of several skeletal features. Particularly significant are the development of an enlarged, keeled sternum and the alula, and the loss of grasping hands.


title: Bird

text: The first large, diverse lineage of short-tailed avialans to evolve were the Enantiornithes, or "opposite birds", so named because the construction of their shoulder bones was in reverse to that of modern birds. Enantiornithes occupied a wide array of ecological niches, from sand-probing shorebirds and fish-eaters to tree-dwelling forms and seed-eaters. While they were the dominant group of avialans during the Cretaceous period, enantiornithes became extinct along with many other dinosaur groups at the end of the Mesozoic era.


title: Bird

text: Many species of the second major avialan lineage to diversify, the Euornithes (meaning "true birds", because they include the ancestors of modern birds), were semi-aquatic and specialised in eating fish and other small aquatic organisms. Unlike the Enantiornithes, which dominated land-based and arboreal habitats, most early euornithes lacked perching adaptations and seem to have included shorebird-like species, waders, and swimming and diving species.


title: Bird

text: The latter included the superficially gull-like "Ichthyornis" and the Hesperornithiformes, which became so well adapted to hunting fish in marine environments that they lost the ability to fly and became primarily aquatic. The early euornithes also saw the development of many traits associated with modern birds, like strongly keeled breastbones, toothless, beaked portions of their jaws (though most non-avian euornithes retained teeth in other parts of the jaws). Euornithes also included the first avialans to develop true pygostyle and a fully mobile fan of tail feathers, which may have replaced the "hind wing" as the primary mode of aerial maneuverability and braking in flight.


title: Bird

text: A study on mosaic evolution in the avian skull found that the last common ancestor of all Neornithes might have had a beak similar to that of the modern hook-billed vanga and a skull similar to that of the Eurasian golden oriole. As both species are small aerial and canopy foraging omnivores, a similar ecological niche was inferred for this hypothetical ancestor.


title: Bird

text: All modern birds lie within the crown group Aves (alternately Neornithes), which has two subdivisions: the Palaeognathae, which includes the flightless ratites (such as the ostriches) and the weak-flying tinamous, and the extremely diverse Neognathae, containing all other birds. These two subdivisions have variously been given the rank of superorder, cohort, or infraclass. Depending on the taxonomic viewpoint, the number of known living bird species varies anywhere from 9,800 to 10,758.


title: Bird

text: The discovery of "Vegavis" from the Maastrichtian, the last stage of the Late Cretaceous proved that the diversification of modern birds started before the Cenozoic era. The affinities of an earlier fossil, the possible galliform "Austinornis lentus", dated to about 85 million years ago, are still too controversial to provide a fossil evidence of modern bird diversification. In 2020, "Asteriornis" from the Maastrichtian was described, it appears to be a close relative of Galloanserae, the earliest diverging lineage within Neognathae.


title: Bird

text: Most studies agree on a Cretaceous age for the most recent common ancestor of modern birds but estimates range from the Early Cretaceous to the latest Late Cretaceous. Similarly, there is no agreement on whether most of the early diversification of modern birds occurred before or after the Cretaceous–Palaeogene extinction event. This disagreement is in part caused by a divergence in the evidence; most molecular dating studies suggests a Cretaceous evolutionary radiation, while fossil evidence points to a Cenozoic radiation (the so-called 'rocks' versus 'clocks' controversy). Previous attempts to reconcile molecular and fossil evidence have proved controversial, but more recent estimates, using a more comprehensive sample of fossils and a new way of calibrating molecular clocks, showed that while according to some studies, modern birds originated early in the Late Cretaceous in Western Gondwana, a pulse of diversification in all major groups occurred around the Cretaceous–Palaeogene extinction event. Modern birds expanded from West Gondwana to the Laurasia through two routes. One route was an Antarctic interchange in the Paleogene. This can be confirmed with the presence of multiple avian groups in Australia and New Zealand. The other route was probably through North America, via land bridges, during the Paleocene. This allowed the expansion and diversification of Neornithes into the Holarctic and Paleotropics. On the other hand, the occurrence of "Asteriornis" in the Northern Hemisphere challenges biogeographical hypotheses of a Gondwanan origin of crown birds.


title: Bird

text: The classification of birds is a contentious issue. Sibley and Ahlquist's "Phylogeny and Classification of Birds" (1990) is a landmark work on the subject. Most evidence seems to suggest the assignment of orders is accurate, but scientists disagree about the relationships among the orders themselves; evidence from modern bird anatomy, fossils and DNA have all been brought to bear on the problem, but no strong consensus has emerged. More recently, new fossil and molecular evidence is providing an increasingly clear picture of the evolution of modern bird orders.


title: Bird

text: , the genome had been sequenced for only two birds, the chicken and the zebra finch. the genomes of 542 species of birds had been completed. At least one genome has been sequenced from every order.


title: Bird

text: These include at least one species in about 90% of extant avian families (218 out of 236 families recognised by the "Howard and Moore Checklist").


title: Bird

text: Being able to sequence and compare whole genomes gives researchers many types of information, about genes, the DNA that regulates the genes, and their evolutionary history. This has led to reconsideration of some of the classifications that were based solely on the identification of protein-coding genes. Waterbirds such as pelicans and flamingos, for example, may have in common specific adaptations suited to their environment that were developed independently.


title: Bird

text: Birds live and breed in most terrestrial habitats and on all seven continents, reaching their southern extreme in the snow petrel's breeding colonies up to inland in Antarctica. The highest bird diversity occurs in tropical regions. It was earlier thought that this high diversity was the result of higher speciation rates in the tropics; however recent studies found higher speciation rates in the high latitudes that were offset by greater extinction rates than in the tropics. Many species migrate annually over great distances and across oceans; several families of birds have adapted to life both on the world's oceans and in them, and some seabird species come ashore only to breed, while some penguins have been recorded diving up to deep.


title: Bird

text: Many bird species have established breeding populations in areas to which they have been introduced by humans. Some of these introductions have been deliberate; the ring-necked pheasant, for example, has been introduced around the world as a game bird. Others have been accidental, such as the establishment of wild monk parakeets in several North American cities after their escape from captivity. Some species, including cattle egret, yellow-headed caracara and galah, have spread naturally far beyond their original ranges as agricultural expansion created alternative habitats although modern practices of intensive agriculture have negatively impacted farmland bird populations.


title: Bird

text: Compared with other vertebrates, birds have a body plan that shows many unusual adaptations, mostly to facilitate flight.


title: Bird

text: The skeleton consists of very lightweight bones. They have large air-filled cavities (called pneumatic cavities) which connect with the respiratory system. The skull bones in adults are fused and do not show cranial sutures. The orbital cavities that house the eyeballs are large and separated from each other by a bony septum (partition). The spine has cervical, thoracic, lumbar and caudal regions with the number of cervical (neck) vertebrae highly variable and especially flexible, but movement is reduced in the anterior thoracic vertebrae and absent in the later vertebrae. The last few are fused with the pelvis to form the synsacrum. The ribs are flattened and the sternum is keeled for the attachment of flight muscles except in the flightless bird orders. The forelimbs are modified into wings. The wings are more or less developed depending on the species; the only known groups that lost their wings are the extinct moa and elephant birds.


title: Bird

text: Like the reptiles, birds are primarily uricotelic, that is, their kidneys extract nitrogenous waste from their bloodstream and excrete it as uric acid, instead of urea or ammonia, through the ureters into the intestine. Birds do not have a urinary bladder or external urethral opening and (with exception of the ostrich) uric acid is excreted along with faeces as a semisolid waste. However, birds such as hummingbirds can be facultatively ammonotelic, excreting most of the nitrogenous wastes as ammonia. They also excrete creatine, rather than creatinine like mammals. This material, as well as the output of the intestines, emerges from the bird's cloaca. The cloaca is a multi-purpose opening: waste is expelled through it, most birds mate by joining cloaca, and females lay eggs from it. In addition, many species of birds regurgitate pellets.


title: Bird

text: It is a common but not universal feature of altricial passerine nestlings (born helpless, under constant parental care) that instead of excreting directly into the nest, they produce a fecal sac. This is a mucus-covered pouch that allows parents to either dispose of the waste outside the nest or to recycle the waste through their own digestive system.


title: Bird

text: Males within Palaeognathae (with the exception of the kiwis), the Anseriformes (with the exception of screamers), and in rudimentary forms in Galliformes (but fully developed in Cracidae) possess a penis, which is never present in Neoaves. The length is thought to be related to sperm competition. For male birds to get an erection, they depends on lymphatic fluid instead of blood. When not copulating, it is hidden within the proctodeum compartment within the cloaca, just inside the vent. Female birds have sperm storage tubules that allow sperm to remain viable long after copulation, a hundred days in some species. Sperm from multiple males may compete through this mechanism. Most female birds have a single ovary and a single oviduct, both on the left side, but there are exceptions: species in at least 16 different orders of birds have two ovaries. Even these species, however, tend to have a single oviduct. It has been speculated that this might be an adaptation to flight, but males have two testes, and it is also observed that the gonads in both sexes decrease dramatically in size outside the breeding season. Also terrestrial birds generally have a single ovary, as does the platypus, an egg-laying mammal. A more likely explanation is that the egg develops a shell while passing through the oviduct over a period of about a day, so that if two eggs were to develop at the same time, there would be a risk to survival. While rare, mostly abortive, parthenogenesis is not unknown in birds and eggs can be diploid, automictic and results in male offspring.


title: Bird

text: Birds are solely gonochoric. Meaning they have two sexes: either female or male. The sex of birds is determined by the Z and W sex chromosomes, rather than by the X and Y chromosomes present in mammals. Male birds have two Z chromosomes (ZZ), and female birds have a W chromosome and a Z chromosome (WZ).


title: Bird

text: In nearly all species of birds, an individual's sex is determined at fertilisation. However, one 2007 study claimed to demonstrate temperature-dependent sex determination among the Australian brushturkey, for which higher temperatures during incubation resulted in a higher female-to-male sex ratio. This, however, was later proven to not be the case. These birds do not exhibit temperature-dependent sex determination, but temperature-dependent sex mortality.


title: Bird

text: Birds have one of the most complex respiratory systems of all animal groups. Upon inhalation, 75% of the fresh air bypasses the lungs and flows directly into a posterior air sac which extends from the lungs and connects with air spaces in the bones and fills them with air. The other 25% of the air goes directly into the lungs. When the bird exhales, the used air flows out of the lungs and the stored fresh air from the posterior air sac is simultaneously forced into the lungs. Thus, a bird's lungs receive a constant supply of fresh air during both inhalation and exhalation. Sound production is achieved using the syrinx, a muscular chamber incorporating multiple tympanic membranes which diverges from the lower end of the trachea; the trachea being elongated in some species, increasing the volume of vocalisations and the perception of the bird's size.


title: Bird

text: In birds, the main arteries taking blood away from the heart originate from the right aortic arch (or pharyngeal arch), unlike in the mammals where the left aortic arch forms this part of the aorta. The postcava receives blood from the limbs via the renal portal system. Unlike in mammals, the circulating red blood cells in birds retain their nucleus.


title: Bird

text: The avian circulatory system is driven by a four-chambered, myogenic heart contained in a fibrous pericardial sac. This pericardial sac is filled with a serous fluid for lubrication. The heart itself is divided into a right and left half, each with an atrium and ventricle. The atrium and ventricles of each side are separated by atrioventricular valves which prevent back flow from one chamber to the next during contraction. Being myogenic, the heart's pace is maintained by pacemaker cells found in the sinoatrial node, located on the right atrium.


title: Bird

text: The sinoatrial node uses calcium to cause a depolarising signal transduction pathway from the atrium through right and left atrioventricular bundle which communicates contraction to the ventricles. The avian heart also consists of muscular arches that are made up of thick bundles of muscular layers. Much like a mammalian heart, the avian heart is composed of endocardial, myocardial and epicardial layers. The atrium walls tend to be thinner than the ventricle walls, due to the intense ventricular contraction used to pump oxygenated blood throughout the body. Avian hearts are generally larger than mammalian hearts when compared to body mass. This adaptation allows more blood to be pumped to meet the high metabolic need associated with flight.


title: Bird

text: Birds have a very efficient system for diffusing oxygen into the blood; birds have a ten times greater surface area to gas exchange volume than mammals. As a result, birds have more blood in their capillaries per unit of volume of lung than a mammal. The arteries are composed of thick elastic muscles to withstand the pressure of the ventricular contractions, and become more rigid as they move away from the heart. Blood moves through the arteries, which undergo vasoconstriction, and into arterioles which act as a transportation system to distribute primarily oxygen as well as nutrients to all tissues of the body. As the arterioles move away from the heart and into individual organs and tissues they are further divided to increase surface area and slow blood flow. Blood travels through the arterioles and moves into the capillaries where gas exchange can occur.


title: Bird

text: Capillaries are organised into capillary beds in tissues; it is here that blood exchanges oxygen for carbon dioxide waste. In the capillary beds, blood flow is slowed to allow maximum diffusion of oxygen into the tissues. Once the blood has become deoxygenated, it travels through venules then veins and back to the heart. Veins, unlike arteries, are thin and rigid as they do not need to withstand extreme pressure. As blood travels through the venules to the veins a funneling occurs called vasodilation bringing blood back to the heart. Once the blood reaches the heart, it moves first into the right atrium, then the right ventricle to be pumped through the lungs for further gas exchange of carbon dioxide waste for oxygen. Oxygenated blood then flows from the lungs through the left atrium to the left ventricle where it is pumped out to the body.


title: Bird

text: The nervous system is large relative to the bird's size. The most developed part of the brain is the one that controls the flight-related functions, while the cerebellum coordinates movement and the cerebrum controls behaviour patterns, navigation, mating and nest building. Most birds have a poor sense of smell with notable exceptions including kiwis, New World vultures and tubenoses. The avian visual system is usually highly developed. Water birds have special flexible lenses, allowing accommodation for vision in air and water. Some species also have dual fovea. Birds are tetrachromatic, possessing ultraviolet (UV) sensitive cone cells in the eye as well as green, red and blue ones. They also have double cones, likely to mediate achromatic vision.


title: Bird

text: Many birds show plumage patterns in ultraviolet that are invisible to the human eye; some birds whose sexes appear similar to the naked eye are distinguished by the presence of ultraviolet reflective patches on their feathers. Male blue tits have an ultraviolet reflective crown patch which is displayed in courtship by posturing and raising of their nape feathers. Ultraviolet light is also used in foraging—kestrels have been shown to search for prey by detecting the UV reflective urine trail marks left on the ground by rodents. With the exception of pigeons and a few other species, the eyelids of birds are not used in blinking. Instead the eye is lubricated by the nictitating membrane, a third eyelid that moves horizontally. The nictitating membrane also covers the eye and acts as a contact lens in many aquatic birds. The bird retina has a fan shaped blood supply system called the pecten.


title: Bird

text: Eyes of most birds are large, not very round and capable of only limited movement in the orbits, typically 10–20°. Birds with eyes on the sides of their heads have a wide visual field, while birds with eyes on the front of their heads, such as owls, have binocular vision and can estimate the depth of field. The avian ear lacks external pinnae but is covered by feathers, although in some birds, such as the "Asio", "Bubo" and "Otus" owls, these feathers form tufts which resemble ears. The inner ear has a cochlea, but it is not spiral as in mammals.


title: Bird

text: A few species are able to use chemical defences against predators; some Procellariiformes can eject an unpleasant stomach oil against an aggressor, and some species of pitohuis from New Guinea have a powerful neurotoxin in their skin and feathers.


title: Bird

text: A lack of field observations limit our knowledge, but intraspecific conflicts are known to sometimes result in injury or death. The screamers (Anhimidae), some jacanas ("Jacana", "Hydrophasianus"), the spur-winged goose ("Plectropterus"), the torrent duck ("Merganetta") and nine species of lapwing ("Vanellus") use a sharp spur on the wing as a weapon. The steamer ducks ("Tachyeres"), geese and swans ("Anserinae"), the solitaire ("Pezophaps"), sheathbills ("Chionis"), some guans ("Crax") and stone curlews ("Burhinus") use a bony knob on the alular metacarpal to punch and hammer opponents. The jacanas "Actophilornis" and "Irediparra" have an expanded, blade-like radius. The extinct "Xenicibis" was unique in having an elongate forelimb and massive hand which likely functioned in combat or defence as a jointed club or flail. Swans, for instance, may strike with the bony spurs and bite when defending eggs or young.


title: Bird

text: Feathers are a feature characteristic of birds (though also present in some dinosaurs not currently considered to be true birds). They facilitate flight, provide insulation that aids in thermoregulation, and are used in display, camouflage, and signalling. There are several types of feathers, each serving its own set of purposes. Feathers are epidermal growths attached to the skin and arise only in specific tracts of skin called pterylae. The distribution pattern of these feather tracts (pterylosis) is used in taxonomy and systematics. The arrangement and appearance of feathers on the body, called plumage, may vary within species by age, social status, and sex.


title: Bird

text: Plumage is regularly moulted; the standard plumage of a bird that has moulted after breeding is known as the "" plumage, or—in the Humphrey–Parkes terminology—"basic" plumage; breeding plumages or variations of the basic plumage are known under the Humphrey–Parkes system as "" plumages. Moulting is annual in most species, although some may have two moults a year, and large birds of prey may moult only once every few years. Moulting patterns vary across species. In passerines, flight feathers are replaced one at a time with the innermost being the first. When the fifth of sixth primary is replaced, the outermost begin to drop. After the innermost tertiaries are moulted, the starting from the innermost begin to drop and this proceeds to the outer feathers (centrifugal moult). The greater primary are moulted in synchrony with the primary that they overlap.


title: Bird

text: A small number of species, such as ducks and geese, lose all of their flight feathers at once, temporarily becoming flightless. As a general rule, the tail feathers are moulted and replaced starting with the innermost pair. Centripetal moults of tail feathers are however seen in the Phasianidae. The centrifugal moult is modified in the tail feathers of woodpeckers and treecreepers, in that it begins with the second innermost pair of feathers and finishes with the central pair of feathers so that the bird maintains a functional climbing tail. The general pattern seen in passerines is that the primaries are replaced outward, secondaries inward, and the tail from centre outward. Before nesting, the females of most bird species gain a bare brood patch by losing feathers close to the belly. The skin there is well supplied with blood vessels and helps the bird in incubation.


title: Bird

text: Feathers require maintenance and birds preen or groom them daily, spending an average of around 9% of their daily time on this. The bill is used to brush away foreign particles and to apply waxy secretions from the uropygial gland; these secretions protect the feathers' flexibility and act as an antimicrobial agent, inhibiting the growth of feather-degrading bacteria. This may be supplemented with the secretions of formic acid from ants, which birds receive through a behaviour known as anting, to remove feather parasites.


title: Bird

text: The scales of birds are composed of the same keratin as beaks, claws, and spurs. They are found mainly on the toes and metatarsus, but may be found further up on the ankle in some birds. Most bird scales do not overlap significantly, except in the cases of kingfishers and woodpeckers.


title: Bird

text: Most birds can fly, which distinguishes them from almost all other vertebrate classes. Flight is the primary means of locomotion for most bird species and is used for searching for food and for escaping from predators. Birds have various adaptations for flight, including a lightweight skeleton, two large flight muscles, the pectoralis (which accounts for 15% of the total mass of the bird) and the supracoracoideus, as well as a modified forelimb (wing) that serves as an aerofoil.


title: Bird

text: Wing shape and size generally determine a bird's flight style and performance; many birds combine powered, flapping flight with less energy-intensive soaring flight. About 60 extant bird species are flightless, as were many extinct birds. Flightlessness often arises in birds on isolated islands, most likely due to limited resources and the absence of mammalian land predators. Flightlessness is almost exclusively correlated with gigantism due to an island's inheren condition of isolation. Although flightless, penguins use similar musculature and movements to "fly" through the water, as do some flight-capable birds such as auks, shearwaters and dippers.


title: Bird

text: Most birds are diurnal, but some birds, such as many species of owls and nightjars, are nocturnal or crepuscular (active during twilight hours), and many coastal waders feed when the tides are appropriate, by day or night.


title: Bird

text: are varied and often include nectar, fruit, plants, seeds, carrion, and various small animals, including other birds. The digestive system of birds is unique, with a crop for storage and a gizzard that contains swallowed stones for grinding food to compensate for the lack of teeth. Some species such as pigeons and some psittacine species do not have a gallbladder. Most birds are highly adapted for rapid digestion to aid with flight. Some migratory birds have adapted to use protein stored in many parts of their bodies, including protein from the intestines, as additional energy during migration.


title: Bird

text: Birds that employ many strategies to obtain food or feed on a variety of food items are called generalists, while others that concentrate time and effort on specific food items or have a single strategy to obtain food are considered specialists. Avian foraging strategies can vary widely by species. Many birds glean for insects, invertebrates, fruit, or seeds. Some hunt insects by suddenly attacking from a branch. Those species that seek pest insects are considered beneficial 'biological control agents' and their presence encouraged in biological pest control programmes. Combined, insectivorous birds eat 400–500 million metric tons of arthropods annually.


title: Bird

text: Nectar feeders such as hummingbirds, sunbirds, lories, and lorikeets amongst others have specially adapted brushy tongues and in many cases bills designed to fit co-adapted flowers. Kiwis and shorebirds with long bills probe for invertebrates; shorebirds' varied bill lengths and feeding methods result in the separation of ecological niches. Loons, diving ducks, penguins and auks pursue their prey underwater, using their wings or feet for propulsion, while aerial predators such as sulids, kingfishers and terns plunge dive after their prey. Flamingos, three species of prion, and some ducks are filter feeders. Geese and dabbling ducks are primarily grazers.


title: Bird

text: Some species, including frigatebirds, gulls, and skuas, engage in kleptoparasitism, stealing food items from other birds. Kleptoparasitism is thought to be a supplement to food obtained by hunting, rather than a significant part of any species' diet; a study of great frigatebirds stealing from masked boobies estimated that the frigatebirds stole at most 40% of their food and on average stole only 5%. Other birds are scavengers; some of these, like vultures, are specialised carrion eaters, while others, like gulls, corvids, or other birds of prey, are opportunists.


title: Bird

text: Water is needed by many birds although their mode of excretion and lack of sweat glands reduces the physiological demands. Some desert birds can obtain their water needs entirely from moisture in their food. They may also have other adaptations such as allowing their body temperature to rise, saving on moisture loss from evaporative cooling or panting. Seabirds can drink seawater and have salt glands inside the head that eliminate excess salt out of the nostrils.


title: Bird

text: Most birds scoop water in their beaks and raise their head to let water run down the throat. Some species, especially of arid zones, belonging to the pigeon, finch, mousebird, button-quail and bustard families are capable of sucking up water without the need to tilt back their heads. Some desert birds depend on water sources and sandgrouse are particularly well known for their daily congregations at waterholes. Nesting sandgrouse and many plovers carry water to their young by wetting their belly feathers. Some birds carry water for chicks at the nest in their crop or regurgitate it along with food. The pigeon family, flamingos and penguins have adaptations to produce a nutritive fluid called crop milk that they provide to their chicks.


title: Bird

text: Feathers, being critical to the survival of a bird, require maintenance. Apart from physical wear and tear, feathers face the onslaught of fungi, ectoparasitic feather mites and bird lice. The physical condition of feathers are maintained by often with the application of secretions from the . Birds also bathe in water or dust themselves. While some birds dip into shallow water, more aerial species may make aerial dips into water and arboreal species often make use of dew or rain that collect on leaves. Birds of arid regions make use of loose soil to dust-bathe. A behaviour termed as anting in which the bird encourages ants to run through their plumage is also thought to help them reduce the ectoparasite load in feathers. Many species will spread out their wings and expose them to direct sunlight and this too is thought to help in reducing fungal and ectoparasitic activity that may lead to feather damage.


title: Bird

text: Many bird species migrate to take advantage of global differences of seasonal temperatures, therefore optimising availability of food sources and breeding habitat. These migrations vary among the different groups. Many landbirds, shorebirds, and waterbirds undertake annual long-distance migrations, usually triggered by the length of daylight as well as weather conditions. These birds are characterised by a breeding season spent in the temperate or polar regions and a non-breeding season in the tropical regions or opposite hemisphere. Before migration, birds substantially increase body fats and reserves and reduce the size of some of their organs.


title: Bird

text: Migration is highly demanding energetically, particularly as birds need to cross deserts and oceans without refuelling. Landbirds have a flight range of around and shorebirds can fly up to , although the bar-tailed godwit is capable of non-stop flights of up to . Seabirds also undertake long migrations, the longest annual migration being those of sooty shearwaters, which nest in New Zealand and Chile and spend the northern summer feeding in the North Pacific off Japan, Alaska and California, an annual round trip of . Other seabirds disperse after breeding, travelling widely but having no set migration route. Albatrosses nesting in the Southern Ocean often undertake circumpolar trips between breeding seasons.


title: Bird

text: Some bird species undertake shorter migrations, travelling only as far as is required to avoid bad weather or obtain food. Irruptive species such as the boreal finches are one such group and can commonly be found at a location in one year and absent the next. This type of migration is normally associated with food availability. Species may also travel shorter distances over part of their range, with individuals from higher latitudes travelling into the existing range of conspecifics; others undertake partial migrations, where only a fraction of the population, usually females and subdominant males, migrates. Partial migration can form a large percentage of the migration behaviour of birds in some regions; in Australia, surveys found that 44% of non-passerine birds and 32% of passerines were partially migratory.


title: Bird

text: Altitudinal migration is a form of short-distance migration in which birds spend the breeding season at higher altitudes and move to lower ones during suboptimal conditions. It is most often triggered by temperature changes and usually occurs when the normal territories also become inhospitable due to lack of food. Some species may also be nomadic, holding no fixed territory and moving according to weather and food availability. Parrots as a family are overwhelmingly neither migratory nor sedentary but considered to either be dispersive, irruptive, nomadic or undertake small and irregular migrations.


title: Bird

text: The ability of birds to return to precise locations across vast distances has been known for some time; in an experiment conducted in the 1950s, a Manx shearwater released in Boston in the United States returned to its colony in Skomer, in Wales within 13 days, a distance of . Birds navigate during migration using a variety of methods. For diurnal migrants, the sun is used to navigate by day, and a stellar compass is used at night. Birds that use the sun compensate for the changing position of the sun during the day by the use of an internal clock. Orientation with the stellar compass depends on the position of the constellations surrounding Polaris. These are backed up in some species by their ability to sense the Earth's geomagnetism through specialised photoreceptors.


title: Bird

text: Birds communicate primarily using visual and auditory signals. Signals can be interspecific (between species) and intraspecific (within species).


title: Bird

text: Birds sometimes use plumage to assess and assert social dominance, to display breeding condition in sexually selected species, or to make threatening displays, as in the sunbittern's mimicry of a large predator to ward off hawks and protect young chicks.


title: Bird

text: Visual communication among birds may also involve ritualised displays, which have developed from non-signalling actions such as preening, the adjustments of feather position, pecking, or other behaviour. These displays may signal aggression or submission or may contribute to the formation of pair-bonds. The most elaborate displays occur during courtship, where "dances" are often formed from complex combinations of many possible component movements; males' breeding success may depend on the quality of such displays.


title: Bird

text: Bird calls and songs, which are produced in the syrinx, are the major means by which birds communicate with sound. This communication can be very complex; some species can operate the two sides of the syrinx independently, allowing the simultaneous production of two different songs.


title: Bird

text: Calls are used for a variety of purposes, including mate attraction, evaluation of potential mates, bond formation, the claiming and maintenance of territories, the identification of other individuals (such as when parents look for chicks in colonies or when mates reunite at the start of breeding season), and the warning of other birds of potential predators, sometimes with specific information about the nature of the threat. Some birds also use mechanical sounds for auditory communication. The "Coenocorypha" snipes of New Zealand drive air through their feathers, woodpeckers drum for long-distance communication, and palm cockatoos use tools to drum.


title: Bird

text: While some birds are essentially territorial or live in small family groups, other birds may form large flocks. The principal benefits of flocking are safety in numbers and increased foraging efficiency. Defence against predators is particularly important in closed habitats like forests, where ambush predation is common and multiple eyes can provide a valuable early warning system. This has led to the development of many mixed-species feeding flocks, which are usually composed of small numbers of many species; these flocks provide safety in numbers but increase potential competition for resources. Costs of flocking include bullying of socially subordinate birds by more dominant birds and the reduction of feeding efficiency in certain cases.


title: Bird

text: Birds sometimes also form associations with non-avian species. Plunge-diving seabirds associate with dolphins and tuna, which push shoaling fish towards the surface. Some species of hornbills have a mutualistic relationship with dwarf mongooses, in which they forage together and warn each other of nearby birds of prey and other predators.


title: Bird

text: The high metabolic rates of birds during the active part of the day is supplemented by rest at other times. Sleeping birds often use a type of sleep known as vigilant sleep, where periods of rest are interspersed with quick eye-opening "peeks", allowing them to be sensitive to disturbances and enable rapid escape from threats. Swifts are believed to be able to sleep in flight and radar observations suggest that they orient themselves to face the wind in their roosting flight. It has been suggested that there may be certain kinds of sleep which are possible even when in flight.


title: Bird

text: Some birds have also demonstrated the capacity to fall into slow-wave sleep one hemisphere of the brain at a time. The birds tend to exercise this ability depending upon its position relative to the outside of the flock. This may allow the eye opposite the sleeping hemisphere to remain vigilant for predators by viewing the outer margins of the flock. This adaptation is also known from marine mammals. Communal roosting is common because it lowers the loss of body heat and decreases the risks associated with predators. Roosting sites are often chosen with regard to thermoregulation and safety. Unusual mobile roost sites include large herbivores on the African savanna that are used by oxpeckers.


title: Bird

text: Many sleeping birds bend their heads over their backs and tuck their bills in their back feathers, although others place their beaks among their breast feathers. Many birds rest on one leg, while some may pull up their legs into their feathers, especially in cold weather. Perching birds have a tendon-locking mechanism that helps them hold on to the perch when they are asleep. Many ground birds, such as quails and pheasants, roost in trees. A few parrots of the genus "Loriculus" roost hanging upside down. Some hummingbirds go into a nightly state of torpor accompanied with a reduction of their metabolic rates. This physiological adaptation shows in nearly a hundred other species, including owlet-nightjars, nightjars, and woodswallows. One species, the common poorwill, even enters a state of hibernation. Birds do not have sweat glands, but can lose water directly through the skin, and they may cool themselves by moving to shade, standing in water, panting, increasing their surface area, fluttering their throat or using special behaviours like urohidrosis to cool themselves.


title: Bird

text: Ninety-five per cent of bird species are socially monogamous. These species pair for at least the length of the breeding season or—in some cases—for several years or until the death of one mate. Monogamy allows for both paternal care and biparental care, which is especially important for species in which care from both the female and the male parent is required in order to successfully rear a brood. Among many socially monogamous species, extra-pair copulation (infidelity) is common. Such behaviour typically occurs between dominant males and females paired with subordinate males, but may also be the result of forced copulation in ducks and other anatids.


title: Bird

text: For females, possible benefits of extra-pair copulation include getting better genes for her offspring and insuring against the possibility of infertility in her mate. Males of species that engage in extra-pair copulations will closely guard their mates to ensure the parentage of the offspring that they raise.


title: Bird

text: Other mating systems, including polygyny, polyandry, polygamy, polygynandry, and promiscuity, also occur. Polygamous breeding systems arise when females are able to raise broods without the help of males. Mating systems vary across bird families but variations within species are thought to be driven by environmental conditions.


title: Bird

text: Breeding usually involves some form of courtship display, typically performed by the male. Most displays are rather simple and involve some type of song. Some displays, however, are quite elaborate. Depending on the species, these may include wing or tail drumming, dancing, aerial flights, or communal lekking. Females are generally the ones that drive partner selection, although in the polyandrous phalaropes, this is reversed: plainer males choose brightly coloured females. Courtship feeding, billing and are commonly performed between partners, generally after the birds have paired and mated.


title: Bird

text: Homosexual behaviour has been observed in males or females in numerous species of birds, including copulation, pair-bonding, and joint parenting of chicks. Over 130 avian species around the world engage in sexual interactions between the same sex or homosexual behaviours. "Same-sex courtship activities may involve elaborate displays, synchronized dances, gift-giving ceremonies, or behaviors at specific display areas including bowers, arenas, or leks."


title: Bird

text: Many birds actively defend a territory from others of the same species during the breeding season; maintenance of territories protects the food source for their chicks. Species that are unable to defend feeding territories, such as seabirds and swifts, often breed in colonies instead; this is thought to offer protection from predators. Colonial breeders defend small nesting sites, and competition between and within species for nesting sites can be intense.


title: Bird

text: All birds lay amniotic eggs with hard shells made mostly of calcium carbonate. Hole and burrow nesting species tend to lay white or pale eggs, while open nesters lay camouflaged eggs. There are many exceptions to this pattern, however; the ground-nesting nightjars have pale eggs, and camouflage is instead provided by their plumage. Species that are victims of brood parasites have varying egg colours to improve the chances of spotting a parasite's egg, which forces female parasites to match their eggs to those of their hosts.


title: Bird

text: Bird eggs are usually laid in a nest. Most species create somewhat elaborate nests, which can be cups, domes, plates, mounds, or burrows. Some bird nests can be a simple scrape, with minimal or no lining; most seabird and wader nests are no more than a scrape on the ground. Most birds build nests in sheltered, hidden areas to avoid predation, but large or colonial birds—which are more capable of defence—may build more open nests. During nest construction, some species seek out plant matter from plants with parasite-reducing toxins to improve chick survival, and feathers are often used for nest insulation. Some bird species have no nests; the cliff-nesting common guillemot lays its eggs on bare rock, and male emperor penguins keep eggs between their body and feet. The absence of nests is especially prevalent in open habitat ground-nesting species where any addition of nest material would make the nest more conspicuous. Many ground nesting birds lay a clutch of eggs that hatch synchronously, with precocial chicks led away from the nests (nidifugous) by their parents soon after hatching.


title: Bird

text: Incubation, which regulates temperature for chick development, usually begins after the last egg has been laid. In monogamous species incubation duties are often shared, whereas in polygamous species one parent is wholly responsible for incubation. Warmth from parents passes to the eggs through brood patches, areas of bare skin on the abdomen or breast of the incubating birds. Incubation can be an energetically demanding process; adult albatrosses, for instance, lose as much as of body weight per day of incubation. The warmth for the incubation of the eggs of megapodes comes from the sun, decaying vegetation or volcanic sources. Incubation periods range from 10 days (in woodpeckers, cuckoos and passerine birds) to over 80 days (in albatrosses and kiwis).


title: Bird

text: The diversity of characteristics of birds is great, sometimes even in closely related species. Several avian characteristics are compared in the table below.


title: Bird

text: At the time of their hatching, chicks range in development from helpless to independent, depending on their species. Helpless chicks are termed "altricial", and tend to be born small, blind, immobile and naked; chicks that are mobile and feathered upon hatching are termed "precocial". Altricial chicks need help thermoregulating and must be brooded for longer than precocial chicks. The young of many bird species do not precisely fit into either the precocial or altricial category, having some aspects of each and thus fall somewhere on an "altricial-precocial spectrum". Chicks at neither extreme but favouring one or the other may be termed or .