Downy woodpeckers
Picoides pubescens
Compiled by Niyati Acharya
Downy Woodpeckers are small versions of the classic woodpecker body plan. They have a straight, chisel-like bill, blocky head, wide shoulders, and straight-backed posture as they lean away from tree limbs and onto their tail feathers. The bill tends to look smaller for the bird’s size than in other woodpeckers.
Downy Woodpeckers give a checkered black-and-white impression. The black upperparts are checked with white on the wings, the head is boldly striped, and the back has a broad white stripe down the center. Males have a small red patch on the back of the head. The outer tail feathers are typically white with a few black spots.
Downy Woodpeckers are small for woodpeckers but medium-sized as backyard birds go (just under 7” long, on average). Their backs have a broad white stripe down the center, and their black wings are marked with white horizontal bars. Their faces are also striped black-and-white, and males show a bright red dot at the backs of their heads.
The species spends most of its time clinging to the trunks and branches of trees, with their specialized feet. Woodpecker feet are zygodactyls: two toes forward, two behind, rather than the usual three forward, one behind arrangement of other birds. Downies will pick and peck at tree bark in search of insects, and they will often crawl out to the tips of smaller branches that larger woodpeckers can’t access. They will eagerly visit feeders for both seeds and suet.
In winter, they join large flocks of chickadees and nuthatches to search the landscape for food. In spring and summer, they nest in tree cavities, especially in soft or rotting wood that their small bills can excavate.
Downies are easily the most common and widespread woodpeckers in the Commonwealth, and their willingness to use young forests, mature forests, or tree-lined suburbs has ensured that their numbers continue to stay strong. Winter counts of this resident species are stable or increasing.
How do Downy Woodpeckers manage to drill holes into the tough bark of trees? The extreme endeavor is made possible by a feat of complex coordination of muscles and breaths that essentially turns the tiny bird into a hammer.
Drilling and tapping behaviors in woodpeckers have long garnered significant attention, given their extreme, high-impact nature. However, how these birds integrate neuromuscular and respiratory systems to produce such high-force, high-frequency behaviors remains poorly understood.
Researchers caught and analyzed eight downy woodpeckers. They filmed them drilling and tapping with high-speed video; measured electrical signals in their head, neck, abdomen, tail and leg muscles to reveal when they contracted; and measured the air pressure and airflow in six of the individuals’ airways. The birds were all eventually released back into the wild.
This approach revealed that in order to strike the wood with forces up to 20 to 30 times their body weight, the birds use their hip flexors and front neck muscles to drive them forward as they peck.
They recruit muscles across the head, neck, hips, abdomen and tail, using their entire body to forge a coordinated hammer, with the neck stiffening on contact in a similar manner to how human wrists do when swinging a hammer.
Sources include: Allaboutbirds.org, Massaudubon.org, Smithsonianmag.com
Photo credit: Louis Agassiz/USFWS, Randy Streufert, Brezinski, David, Sudia, Dan/USFWS
