by Lisa Bate
When you look into a recently burned forest, what do you see? Destruction and loss? Or can you sense the pulse of new life created by stand-replacement fires? Every species has unique needs. For many plant species, fire provides a new lease on life by releasing abundant nutrients resulting in vigorous growth. For many wildlife species, fire also provides a pulse of concentrated foraging resources that allows them to not only survive, but to thrive. The Black-backed Woodpecker (Picoides arcticus) is one of these wildlife species. Indeed, it is so strongly associated with stand replacement fires that without periodic fire on our western landscapes, Black-backed Woodpeckers are thought to be vulnerable to local or even regional extinctions (extirpations).
The Black-backed Woodpecker is considered a rare and irruptive species, mainly found in recently burned coniferous forests. They can also be found, however, in lower densities along the edges of older burned areas, avalanche paths, flooded areas, and forests with beetle kill. The key to finding this species is to look where there are dying, and recently dead, trees. For these are the trees colonized by the highly prized round headed (Ceramicidae) and flat headed (Buprestidae) wood-boring beetles. The larvae from these eggs comprise the majority of a Black-backed’s diet and are rich in fat and energy.
The Black-backed Woodpecker is highly specialized in its ability to detect and obtain wood-boring larvae, more so than any other woodpecker species in our area. To extract these larvae, Black-backeds must excavate into the hard sapwood where the young larvae develop. This is made easier by their modified rib cage and skull that endure the hard pounding needed for the job. Black-backed Woodpeckers will also feed on engraver and mountain pine beetles and their larvae; they obtain these prey by pecking, gleaning, or scaling (removing outer layer of bark) on tree trunks and logs. Black-backed Woodpeckers help in the biological control of many insects considered forest pests.
The Black-backed is a medium-sized woodpecker averaging 23 cm (9.1 in) in length. They are distinct in that they are completely black on the back, hence its name. On the closely-related American three-toed Woodpecker (Picoides dorsalis), you will see some white on the back. Black-backed Woodpeckers are also black on the back of the head, wings, and rump. The male can be distinguished from the female by its yellow cap (instead of red as found on most woodpeckers). Along with the American Three-toed-Woodpecker, the Black-backed Woodpecker differs from other woodpeckers in our area by only have three toes: two facing forward and one facing backwards. All other woodpeckers in our area have four toes. Black-backed Woodpeckers have white on their bellies and throat; their flanks are white with black barring. Their scientific name Picoides comes from the Latin word Picus meaning “woodpecker” and the Greek word -oides meaning “resembling”. The species name arcticus comes from the Greek word arktikos meaning “northern”. This helps to describe their range which coincides with the northern limit of montane coniferous forests across North America. They can be found as far south as the Sierra Nevada range in California; in the Rocky Mountains, however, their range only extends to the Black Hills in South Dakota and northwest Wyoming.
Black-backed Woodpeckers are primary cavity-nesters, meaning that they are the first to excavate a nest cavity into a tree. Secondary cavity-nesters, like swallows, are not capable of excavating nest cavities on their own, but will readily occupy a Black-backed’s cavity in subsequent years. The call of the Black-backed Woodpecker is described as a sharp “chek” and the drum is easily distinguished from other woodpecker drums by it slower, longer, and accelerating beat. Best of all is its harsh rattle call which reminds me of the sound a diving board makes as a swimmer jumps off: https://www.allaboutbirds.org/guide/Black-backed_Woodpecker/sounds.
How Black-backed Woodpeckers detect and move to large burn areas on our landscape is not well understood. It may simply be opportunistically, but it may be more complex. Perhaps they can detect wood-boring beetles at great distances? Many insects exude pheromones, or chemical aromas that have distinct messages. For example, mountain pine beetles inhabiting a tree release a pheromone that tells other beetles that the tree is already inhabited. Then the investigating beetle will have to find another tree in which it can lay its eggs. This is how pheromone packets hung on large, stressed trees prevent beetles from attacking it.
Biologists wonder if certain wood-boring beetles may exude a pheromone that Black-backed Woodpeckers can detect from great distances away. Consider wood-boring beetles in the genus Melanophila (fire-loving). Commonly known as “fire beetles”, these insects can detect forest fires up to 100 km (60 miles) away. Researchers have found that these beetles have unique sensors on the sides of their bodies that can detect infrared energy from fires. The infrared energy is then converted into mechanical energy by these sensors, informing the insect of the direction and distance of the nearest fire. This is important because freshly burned trees are the only place where the fire-beetle larvae can develop. Firefighters have often reported large numbers of these beetles arriving in forests as they clear a fire line and the landscape is still smoking.
Conservation concerns for this species include fire suppression and salvage logging. Research has shown that in stand-replacement burned forests, Black-backed Woodpeckers select areas with the highest densities of snags (standing dead trees). Retention of the bark is critical if the trees are to be colonized by wood-boring beetles and provide foraging resources for woodpeckers. Salvage logging operations are known to adversely affect Black-backed Woodpecker habitat; therefore conserving select forest stands in burned areas is important for maintaining viable populations of this species.
Interested in seeing Black-backed Woodpeckers? Visit recently burned forests that have burned within the past three years; this timeline coincides with the beetle larvae life cycle. In older burned areas, focus on the perimeter of the burn where larger trees that still retain their bark may be dying or have recently died. Then stand still and listen. Follow the sounds of calling, drumming, tapping, and excavating as these woodpeckers defend their territories and seek the juicy wood-boring beetle larvae.