oak savanna

Red-headed Woodpecker

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A red-headed woodpecker in flight. Photo by Arlene Koziol

A red-headed woodpecker in flight. Photo by Arlene Koziol

Boisterous in the spring and summer, gliding from dead snag to dead snag, the winter red-headed woodpecker instead rests on a snag, content to take in the snowy scene on a January afternoon. On approach, I hear the chatter of two red-headed woodpeckers, but unlike their lurid and sweeping flights of summer, the bird on this day—like I do—sits on a branch and hardly moves.

Unusual, I think, to have overwintering red-headed woodpeckers. I wonder if a feeder nearby has provided the extra resources for winter, but upon researching the overwintering habits of the bird, I find that its characteristic habitat, the oak savanna, will provide the resources for winter. Acorns, cached for winter, will provide high energy food over the course of these dark winter months. Where there are bumper crops of acorns, you’ll often find overwintering red-headed woodpeckers.

Located in a wet draw of silver maples between two oak woodland and savanna areas, these red-headed woodpeckers likely have a buffet of acorns to feed on. I wonder if other woodpeckers, of which I noticed red-bellied, downy, hairy, and a northern flicker, might steal the acorns. Yet, the red-headed woodpeckers are likely up for the task of defending their caches; during the breeding season, red-headed woodpeckers are known to fiercely defend their nest and territory, with reports of the birds raiding northern flicker and eastern kingbird nests after fights with the parents. In hindsight, I should have checked the abundant cavities in the decaying silver maples to see if there were any cached acorns.

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Hope Lake Bog, where these woodpeckers are located, is actively being restored to oak savanna and woodland. The fact that these woodpeckers are overwintering here and are doing so in all likelihood because of a large acorn crop, has interesting implications for management of the site.

Since clearing buckthorn from large portions of the site, the open understory impresses under giant white oak trees. One of the few things missing here is a prescribed fire to stimulate understory herbs and clear out areas of brambles. Yet, a prescribed fire will also decrease the germination of acorns, with the intensity of the burn in turn decreasing the rate of germination in acorns. With the apparent bumper crop of acorns, the question lingers whether we should wait a year to implement a prescribed burn at the site. Another missing element of the site is young oak saplings to replace the giants in the canopy.

Prescribed burns in Hope Lake Bog result in patchy areas of unburned ground, perfect for germinating acorns. Photo by Drew Harry

Prescribed burns in Hope Lake Bog result in patchy areas of unburned ground, perfect for germinating acorns. Photo by Drew Harry

While concerns over acorn germination are legitimate, the dynamics of fire in the oak ecosystem reveal an even more complex situation. In the picture below, you’ll see that after a fire through an oak leaf litter, there are considerable patches of unburned areas. These refuges may provide enough refuge to promote germination of acorns. As you can see, a simple natural history observation (hmm it’s odd that these red-headed woodpeckers are overwintering) can have cascading effects and implications for the restoration and management of the whole system. And we’re delighted to have these brilliant members of the ecosystem to alert us of changes on the ground that we might have missed.

Written by Drew Harry, Faville Grove Sanctuary land steward

Red-headed Woodpecker

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One of the most dazzling birds in Wisconsin simultaneously occurs in one of the most enchanting natural communities. The red-headed woodpecker in an oak savanna is a sight to behold.

Not to be confused with red-bellied woodpeckers, which also have a red head, the red-headed woodpecker has a sparkling crimson head, neck, and face while red-bellied woodpeckers only have red on the back of the head with gray faces and throats.

You might notice the red-headed woodpecker in flight among oaks trees with an open understory, and you can't miss its jet black fathers, checkered with pure white on parts of the wing, tail, and the entirety of the breast.

Red-headed woodpecker, photo by Arlene Koziol

Red-headed woodpecker, photo by Arlene Koziol

A purposeful bird, this woodpecker's flight takes a more direct path than other woodpeckers, and you'll typically see red-headed's flying rather straight routes from oak to oak and dead snag to dead snag. It's a bird that, when observed, seems to have no indecision.

An area of varied decision-making comes with the bird's diet, which is omnivorous and among the most diverse of all woodpecker diets. Insects make up a large proportion of prey items during summer, and red-headed woodpeckers are experts at catching insects mid-air. They will also consume and cache acorns, which are supplemented by fruits, nuts, seeds, mice, eggs, and even snakes and lizards.

Red-headed woodpecker, photo by Arlene Koziol

Red-headed woodpecker, photo by Arlene Koziol

Moreover, in studies of woodpecker habitat partitioning, red-headed woodpeckers were found to forage the full range of a dead snag, from top to bottom, and showed no preference for small or large diameter snags, whereas a bird like the downy woodpecker will forage on small diameter trees at restricted ranges.

Hardy enough to spend the winter in Wisconsin, a few red-headed woodpeckers remain each year, but many will migrate slightly south of the snow line. A study in Missouri found that high mast production of acorns, walnuts, and hickories was related to high overwintering numbers of red-headed woodpeckers; it's likely that those birds overwintering in Wisconsin found an excellent crop of acorns.

Red-headed woodpecker and nestling, photo by Arlene Koziol

Red-headed woodpecker and nestling, photo by Arlene Koziol

Additionally, the birds lay 4 to 7 eggs, with some laying up to ten, and red-headed woodpeckers will often raise a second brood. 

With its range of adaptations, one might expect the red-headed woodpecker to be common throughout the state. However, the bird is a Wisconsin species of Special Concern, and the North American population has been cut in half over the past few decades, while the Wisconsin population has declined 60-70%.

It's impossible to pin down an exact cause of this mysterious decline, but let's use Faville Grove Sanctuary as an example of how these populations have declined (and how they can recover).

The Lake Mills Ledge has been restored to an oak savanna with scattered, large diameter bur and white oak trees. After pasturing ceased decades ago—and due to fire suppresion—buckthorn and honeysuckle invaded the understory, and black cherries, elms, and boxelders profused between and among the oak trees. This led to canopy closure, and the restricted space didn't allow red-headed woodpeckers to catch insects or survey from perches.

It's also possible that dead trees and snags were removed from this small forested stand and used for firewood, which would have effectively eliminated nesting cavity habitat for the woodpeckers. Prior to habitat acquisition and restoration, the Lake Mills Ledge was a small island in an agriculturally dominated landscape—where European starlings were frequent, and likely attacked any red-headed woodpeckers inspecting a cavity.

Spring in a Wisconsin oak savanna, photo by Joshua Mayer

Spring in a Wisconsin oak savanna, photo by Joshua Mayer

The effect of restoration on this small savanna has had tremendous positive effects on the red-headed woodpeckers. Clearing of invasive brush and trees has restored the savanna structure, and provides the vistas that red-headed woodpeckers use to pick out prey items. Girdling (removing the cambium and disrupting the flow of nutrients, which kills the tree) of select trees, including a clump of large diameter black willow, has allowed for the desirable characteristics that red-headed woodpeckers look for in a home: large diameter trees flushed of bark, clusters of dead snags, and a high density of dead limbs, especially limbs close to the ground. Lastly, the restoration to native plant communities in the surrounding landscape has made it less likely that starlings will attempt to disrupt nesting activities.

This habitat restoration has proven beneficial to other species as well. Last year we found breeding bluebirds, northern flickers, and downy woodpeckers among the snags.

Red-headed woodpeckers are not an area-sensitive species, meaning they don't need large tracts of habitat for breeding success. Rather, a few dead trees mixed among some living oaks will do just fine. Thus, there is opportunity for private landowners and urban areas to restore populations of red-headed woodpeckers. The solutions prove to be rather simple: cutting invasive brush, and thinning and girldling trees. While the bird's decline remains mysterious, its recovery is less so.

Written by Drew Harry, Faville Grove Sanctuary land steward