Wilderness Underfoot: A head built for hammering

StoryImage( ‘/Images/Story//Auto-img-115091646729607.jpg’, ”, ‘An easy bird to identify – The red-headed woodpecker, Melanerpes erythrocephalus, is the only woodpecker in the Eastern U.S. with a completely red head.’);

Just watching a red-headed woodpecker whacking its bill against solid wood is enough to leave you with a headache; how does this bird avoid brain damage?

Like its other wood-pecking kin, the red-headed woodpecker is aptly suited for the brain-numbing task of pounding on wood. Inside its skull is a layer of impact-absorbing spongy bone that holds the brain securely in place. For added protection, the layer of cerebrospinal fluid between the brain and the skull is quite thin, preventing the brain from sloshing around and shearing.

Shearing, or twisting, is the major cause of brain injury in any kind of animal. To avoid shearing, this bird prevents any rotation of its head while swinging straight forward with pinpoint accuracy.

Relying on these adaptations, the red-headed woodpecker is able to withstand repetitive strikes against wood that snap its head back at forces as high as 10 g. (To get a sense of that force, note that roller coaster riders typically experience a maximum of 3 or 4 g, while fighter pilots risk losing consciousness at anything more than 9 g for a sustained duration.)

This bird doesn’t spend as much time as its wood-pecking kin pounding trees in search of insects. Instead, it prefers to nab insects on the fly. And while it may occasionally eat the eggs of other birds, the greater part of its diet is actually made up of nuts, seeds, grain and berries. The red-headed woodpecker will carefully shell and then store nuts and seeds for the winter, stashing them in tree hollows or under loose bark. And as the food supply diminishes over the winter, it usually migrates south in search of better pickings. Birds in our region winter over along the larger river valleys of central and southern Illinois.

If you hear the telltale tapping of this woodpecker, it may mean that breeding season has arrived. From April through July, it ambitiously hammers large, deep holes in trees to reach hollows in which nests can be built. To knock out suitable nesting sites, the woodpecker needs old growth forests, where long-lived trees have succumbed to insects, weather and burrowing animals.

But with so much of our woodland being cleared or heavily managed, the red-headed woodpecker has lost habitat and its numbers have declined. “Forest management” has often meant harvesting old growth trees and clearing those that are damaged. Although this bird is still widespread across the Eastern U.S., it is not as common as it once was.

From the June 21-27, 2006, issue

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