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Movement Mechanisms of Gyps himalayensis (Himalayan Vultures) in the Central Asian Flyway



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SHERUB, , 2017. Movement Mechanisms of Gyps himalayensis (Himalayan Vultures) in the Central Asian Flyway [Dissertation]. Konstanz: University of Konstanz

@phdthesis{Sherub2017Movem-39799, title={Movement Mechanisms of Gyps himalayensis (Himalayan Vultures) in the Central Asian Flyway}, year={2017}, author={Sherub}, address={Konstanz}, school={Universität Konstanz} }

2017-08-09T09:12:24Z 2017-08-09T09:12:24Z In a space varying from sub-atomic to cosmic scales, nothing is static. As Heraclitus stated half a millennium B.C.: ´Panta rhei´ - everything is constantly on the move.<br />Seasonal wildlife movements are often described and characterized as migrations, which may have evolved from dispersal movements. Animal movements per se may not have captured human attention from the beginning, but animal migrations have since Aristotle. Apparently, migratory movements were abundant throughout the millennia, and individual survival and population processes depended on them. The magnitude of migration phenomena on earth has dwindled with global species extinction and population decline. Numerous such migration phenomena may become history, and more of them will vanish in case our efforts for species conservation fail.<br />The phenomenon of animal migration has captivated scientific interest, and mysteries of wildlife movements are being researched, deciphered and understood. In general, wildlife movements are described in the forms of various migration and five movement types: i) dispersal, ii) nomadic iii) pursuing, iv) escape, and v) spreading. Wildlife migrations can also take the form of partial migration, when only a part of a population migrates seasonally. Partial migration can be found both within long-distance and altitudinal migrations.<br />Movement study in wildlife has begun with simple marking on animal such as with metal or colour bands in early 20th century. In the later part of 20th animal movement studies were performed using satellite tracking, and only recently have GPS point locations been recorded for birds on a global scale. Researcher have now begun to use miniature solar-powered light weight hardware with single to multi-sensor biologgers, efficient to collate animal behaviour via recordings of an individual´s activity (mostly through 3D-ACC sensors) and its exact spatial locations (via GPS sensors). Through the use of 3D-acceleration sensors, one can now also estimate the movement energy via the calculation of the overall dynamic body acceleration (ODBA). This measurement is sufficiently correlated to the overall energy expenditure of individuals to allow for comparisons among and between species.<br />The most modern bio-logging units are remotely programmable which allow researchers to remotely manage sampling regimes. Movement data from bio-loggers that are back-packed on the birds are most efficiently and automatically read out to online database (such as Movebank) via GSM or GPRS mobile network communication systems.<br />For my movement research, e-OBS GmbH solar-powered tags with GPS and ACC sensors, packaged with GSM and GPRS communication facilities were used. The e- OBS bio-logger can be remotely managed via an internet interface, either to collect low or high resolution (1Hz) GPS point data. Every day the bio-logger relays five GPS fixes to the Movebank online database, whereas with a GPRS package, all onboard data (GPS and ACC) are automatically uploaded to Movebank when the tagged bird is within the mobile network. Along with high resolution GPS data, I have used 13 environmental parameters available from the Movebank’s EnvDATA system which influence the vulture movement.<br />In the Asian landscapes, data from animal migrations or movement research are very scanty. However, there is outstanding research on Bar-headed Goose (Anser indicus) migration, other notable studies in Asia are: - the migration of Common Cuckoo (Cuculus canorus) and Common Swift (Apus apus pekinensis). Otherwise, movement studies in three major Asian avian migration flyways have been mostly focussed on the understanding of the spread of avian influenza.<br />Research on vultures across this continent is also scarce. Across Asia, some conservation, pharmacological and mortality studies have been conducted on scavengers, but movement research on Asian vultures is almost non-existing. Otherwise, very little about the movement of vultures in Asia is known.<br />For the first time, this study focuses on the annual movements of the Himalayan Vulture (Gyps himalayensis). I define annual movements is a composite of biannual seasonal migrations from summer to winter areas, daily survival, locomotion and exploratory or continuous nomadic flight. I have chosen this species to study for manifold reasons. Raptors belonging to the vulture taxonomic group are critically endangered around the world, sixteen of the 23 species are enlisted in the threatened category. Himalayan Vulture is a near-threatened species with existing estimated population below 334,000 individuals. It is the heaviest (6-12kg) flying bird in Asia which performs biannual seasonal migratory movements across the Himalayas, and an obligate scavenger making it one of the best species to understand flight mechanisms, migration and annual movements. Vultures are soaring raptors popularly known to harvest wind energies, such as thermals and orographic uplifts as well as tail winds for energy conserving movements.<br />In this study of the Himalayan Vultures, I have assessed the survival and annual movements, flight characteristics and annual movements in relation to environmental factors and flight mechanisms over the Himalayas in the thin air.<br />I back-packed eObs bio-loggers on 18 free ranging and wild Himalayan Vultures, mostly immatures and juveniles or nonbreeding sub-adults. During the first year of the experiment, five of the 18 Himalayan Vultures died en route to their summer areas during their northward seasonal migration. In the assessment of survival and annual movements, I looked at mortality depending upon environmental parameters and initial departure flight distance from winter areas. I demonstrate that en route, migration mortality in Himalayan Vultures is about 27%. It is observed that those dead individuals during migration flew north directly against the north-south meridional head winds, less able to find and use thermal uplifts, and also remained in high density human settlement areas with high humidity and high temperatures. In contrast, those individuals that survived who were able to find thermal uplifts, maintained optimal flight height above the grounds, chose to stay away from high density human settlement and remained in overall higher altitude locations with low temperatures, and their initial migration distance until their first stopover was > 1500km. Mean annual cumulative distance travelled by Himalayan Vultures is 31578 km, and mean of summer movement range is quadruple times the mean winter movement range. The movement tracks and movement range confirms that Himalayan Vultures are truly a migratory species.<br />In the analysis of flight characteristics and annual movements, I analysed how flight characteristics are affected by 13 selected environmental factors. Animals are in constant interaction with abiotic environmental parameters in their movements. A movement may entail seasonal migratory movements and daily movements in both summer and winter areas. I provide a descriptive investigation of flight characteristics of annual movements and annual navigation pathways of the Himalayan Vulture in Asia. I show the environmental conditions that vultures prefer for their living. This examination also demonstrates that vultures migrate to warmer climes in winter, at altitudes below 3800m, and summer in areas of altitudes above 4000m. In the winter, vultures move from lower NDVI to higher NDVI areas. I illustrate that vultures in their summer range are exposed to stronger thermal and orographic uplifts, higher surrounding temperature with drier atmospheric humidity and lower precipitation. Flight height above the ground in summer areas is two times the winter flight height (mean range 180-340m). With this annual movement study, I showcase the north-south and east-west movement range extension of the Himalayan Vultures in Asia.<br />One of the primary quests in this study was also to understand the flight mechanisms of the Himalayan Vultures over the surging mountains of the Himalayas coupled with thin air. Soaring raptors can fly at high altitudes of up to 9000 meters, and Himalayan Vultures are known to fly at around 7000 meters. Using high resolution circle or thermalling GPS data (1Hz), from 50-6500 meters above sea level, a 2-fold range of air densities, I assessed the behavioural adaptation to the flight into thin air. People’s quest to unravel how birds fly long journeys during their migration are still a scientific challenge. While quite a number of studies have been conducted to understand the physiological adaptations of flight mechanisms, the specific mechanisms underlying the behavioural adjustments to high-altitude flights are largely unknown. To create the necessary lift to support the same weight and maintain soaring flight in thin air, birds might modify lift coefficient by biophysical changes, such as wing posture and increasing the power expenditure. Alternatively, they can change their flight characteristics. We show that vultures use the latter and increase circle radius by 35% and airspeed by 21% over their flight altitude range. These simple behavioural adjustments enable vultures to move seamlessly during their annual migrations over the Himalaya without increasing energy output to flight in high elevations.<br />Finally, I recommend existing movement data sets can be analysed comparatively to better understand annual movement characteristics, migration and navigation, landscape level energetics, daily activity pattern, as well as time and energy budgets. Given its wide range distribution, I strongly suggest and call for collaboration among all the Himalayan Vulture range countries for the conservation management of the species as the species use vast expanse of Asian landscape. I also advice to use these movement data to proactively plan for infrastructure development and installations. Furthermore, I also recommend immediate future research as to understand the Himalayan Vulture foraging behaviour and herding movement. I propose that cremation of human corpses in sky burials by Buddhist and Parsee in Asian landscape be encouraged and continued with caution of the use of NSAIDs. Attention is also drawn on how bio-loggers with high resolution and multi-sensor capabilities on birds will serve as an independent real-time mobile weather buoy, which in turn can also serve as sentinels for various weather fronts. Similarly, real time analysis of behavioural (ACC) data may eventually be used to predict impending natural disasters. eng Sherub 2017 terms-of-use Movement Mechanisms of Gyps himalayensis (Himalayan Vultures) in the Central Asian Flyway Sherub

Dateiabrufe seit 09.08.2017 (Informationen über die Zugriffsstatistik)

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