Bird Bio: Black-backed Woodpecker

bbwoThe Black-backed Woodpecker (Picoides arcticus) is wide-ranging but uncommon in the northern coniferous forest of the US and Canada, with a long finger of its distribution extending southward into the high elevation conifer forests of Washington, Oregon, and California. This species is rare on the landscape, making it challenging for scientists to fully understand its habitat needs, behavior, and life history. Cornell’s Birds of North America calls the Black-backed Woodpecker, “one of the most enigmatic woodpeckers.” Much of what is known about Black-backed Woodpeckers is related to their reliance on fire, and their specialized adaptations to life in recently burned forests.

The all-black back that gives this woodpecker its name, and its dark head and neck and bulky body shape, are helpful for distinguishing it from similar looking species such as the American Three-toed and Hairy Woodpeckers. Females have a simple, white “moustache” stripe on the face, while males also have a bright golden patch on the top of the head. This bird’s deep, glossy black plumage camouflages it against the bark of scorched tree trunks as it forages and drums.

The Black-backed woodpecker has two toes that face forward and one that faces back – this species and the American Three-toed Woodpecker are the only two birds in North America that lack a fourth toe. The absence of a back toe likely aids this species in foraging – the bird can pivot farther back while preparing to deliver a blow to a tree trunk, which helps make the blow more forceful. Of all the woodpecker species in the genus Picoides, the Black-backed Woodpecker has the most specialized skull for absorbing shock during the forceful pounding of wood excavation.

These adaptations for forceful excavation help the woodpeckers dig deep into tree trunks for the larvae of wood-boring beetle species that quickly infest a forest after a fire. Around 75% of the Black-backed Woodpecker’s diet consists of these larvae – much more than most other woodpecker species. It is also known to eat tree cambium, some fruits, and even acorns. One of the great mysteries of the Black-backed Woodpecker is how high numbers of the birds are able to quickly find relatively rare and scattered burned forests to exploit ephemeral food and nesting resources. Current research on the species is aimed at trying to solve this puzzle.

Although Black-backed Woodpeckers are most abundant in recently burned forests, they can also be found in unburned conifer forests that have had outbreaks of wood-boring beetles. In the western US, such outbreaks are often considered destructive events – however, for the Black-backed Woodpecker, they are critical for survival. In both burned and unburned, green forests, this species needs forest stands with lots of dead trees, and live trees containing dead tops, dead limbs, and fungal infestations that soften wood for foraging and nesting. They appear to prefer older and unlogged forests to highly managed forests, probably because certain management activities reduce the amount of dead and dying trees. The Black-backed Woodpecker is especially rare in unburned, green forests. Very little is known about their habitat requirements in areas that have not recently experienced a fire, a topic of current study in Oregon and California.

Black-backed Woodpeckers excavate nests in dead or dying trees, and in Oregon and northern California seem to prefer Lodgepole Pine, Ponderosa Pine, and Western Larch for nesting. The male does most of the work of excavation, and both males and females incubate the eggs. Once the young hatch, both parents work to feed and care for them. As nestlings grow older, they become extremely vocal and aggressive in begging for food, sometimes even attacking their parents when they attempt to clean the nest. The young fledge from the nest a little less than one month after hatching. Within their territories, both the males and the females can be aggressive toward intruders, exhibiting fascinating threat displays; they spread their wings, swing their bills from side-to-side, and raise the feathers on the top of the head to show their displeasure. They also will give the “scream-rattle-snarl” call, the most complex call made by any Picoides woodpecker.

The Black-backed Woodpecker is a Partners in Flight focal species for coniferous forests in California. Their strong association with forest fire and the cycles of wood-boring insect outbreaks make them an excellent indicator of these complex forest patterns. Although the rarity of these birds makes their population status unclear, it is thought that their sensitivity to human disturbance puts them at risk for population declines. The CalPIF Coniferous Forest Bird Conservation Plan contains management recommendations for the Black-backed Woodpecker, as well as other forest birds with similar habitat requirements.

References

CalPIF (California Partners in Flight). 2002. Version 1.1. The coniferous forest bird conservation plan: a strategy for protecting and managing coniferous forest habitats and associated birds in California (J. Robinson and J. Alexander, lead authors). PRBO Conservation Science, Petaluma, CA. http://www.prbo.org/calpif/plans.html.

Csuti, B., A.J. Kimerling, T. A. O’Neil, M.M. Shaughnessy, E.P. Gaines, and M.M. P. Huso. 1997. Atlas of Oregon wildlife: distribution, habitat, and natural history. Oregon State University Press, Corvallis. 492 pp.

Dixon R.D., and V.A. Saab. 2000. Black-backed Woodpecker (Picoides arcticus). In The Birds of North America, No. 509 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadephia, PA.

Sibley, David. The Sibley Guide to Bird Life and Behavior. New York: Alfred A. Knopf. Inc., 2001

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