The Great Woodpecker vs. Squirrel War
We hope you enjoy this fantastic post from guest author, Kyle Chen. Kyle is a student at Dougherty Valley High School in San Ramon, CA and has been a volunteer on our Woodpecker Cavity Cam Zooniverse Project since we launched earlier this year. He wrote this essay about his experience for one of his classes. Thanks, Kyle!
As a citizen scientist, I’ve found the Woodpecker Cavity Cam Project to be a unique and interesting way to contribute to research on red-headed woodpeckers and their nesting ecology. Whether it’s observing woodpecker behavior, documenting visits from different animals, or discussing questions with the research team, I’ve gotten a fascinating glimpse into the world of woodpeckers and their cavity habitats.
For me, the most fascinating interactions are between red-headed woodpeckers and other species visiting the woodpeckers’ cavity. Trespassers come in all shapes and sizes, from secondary cavity nesting birds like bluebirds and nuthatches to the rarer fishers or minks.
But there’s no competition for the most persistent antagonist of them all: the squirrel. From the nocturnal flying squirrel to the bushy-tailed eastern grey squirrel, these visitors seem like a constant presence at the woodpeckers’ cavity nests. Day and night, squirrels will often slink into view, circling woodpecker cavities and vying for possession of a new shelter. Apparently, woodpeckers must remain vigilant at all hours to protect their homes from squirrel takeovers.
As you might imagine, the clash of woodpeckers and squirrels has led to some exciting footage. Here are a few of the different scenarios.
Invasion of the Flying Squirrels
The nocturnal, large-eyed flying squirrels are by far the most hostile. Despite their small size, flying squirrels are surprisingly vicious, and have a long track record of usurping nesting cavities from birds (McCormick et al. 2004).
In the video below, a red-bellied woodpecker is caught unawares while roosting in a cavity. The flying squirrel carefully peeks inside, and sees no opposition or alert sentry. Taking advantage of the opportunity, the squirrel darts inside in a flash, and after a bit of struggle inside the cavity, the unfortunate woodpecker is kicked out unceremoniously!
This next video shows another tactic employed by flying squirrels. As you can see, the squirrel reaches inside the cavity and attempts to drag the red-headed woodpecker out from its nest. In this instance, the animals briefly skirmish just outside the cavity and it’s not clear who is the victor. While the woodpecker does get wrenched out, the squirrel also loses its footing and plummets out of frame.
Below, a still photo of the exchange captures this chaotic battle, with the squirrel hanging on for dear life.
Once squirrels drive out the previous inhabitant, they readily occupy the new cavity and use it as a shelter or storage cache for acorns and other nuts. Seen in this video are three squirrels clambering in and out of the now vacant cavity as if it were their own.
Woodpecker Defensive Maneuvers
For their part, red-headed woodpeckers don’t take intrusions lying down. Studies show red-headed woodpeckers vigorously defend their cavities from encroachment by other animals (Ingold 1989)—and based on footage from the Woodpecker Cavity Cam, squirrels are no exception. Oftentimes, all it takes is a quick and powerful show of force from a woodpecker to scare off squirrel intruders. A common pattern is for the squirrel to peek in, get pecked by the alert woodpecker, and immediately flee the scene.
In fact, multiple squirrels can be held at bay by an alert woodpecker. In the video below, notice the two juvenile flying squirrels observing in the top right section of the video, while a third is swiftly repelled by the woodpecker.
Even a young, nestling red-headed woodpecker can sometimes fend off a squirrel, with the right amount of determination!
According to the research team, the squirrels in these scenarios are likely performing a kind of reconnaissance. They "test" a woodpecker in the cavity several times by approaching the hole, but will retreat if they find the woodpecker too tough of an adversary.
Revenge of the Woodpeckers
Woodpeckers aren’t always successful at driving off squirrels, and the “turnover” for cavity possession can be unpredictable. But even with a squirrel already inside the cavity, red-headed woodpeckers aren’t afraid to mount a counterattack to try to reclaim their nest.
In this video, the red-headed woodpecker positions itself right up to the hole and fiercely pecks at the squirrel hiding inside the cavity. It appears that the squirrel is attempting to fight back as well, but the woodpecker retracts its head too quickly for the squirrel to make contact.
Here, a fledgeling observes the occupying red squirrel. Both retreat when the adult red-headed woodpecker executes a flyback attack.
Approximately a minute later, while the squirrel is climbing around outside, another decisive aerial attack causes the squirrel to scramble away. Victory for the red-headed woodpecker!
Red-headed woodpeckers can be vigilant and aggressive defenders of their cavity nests, even against determined squirrel intruders. That’s just as well, since it’s unlikely that there will be a truce in the Woodpecker v. Squirrel war anytime soon; as oak savannas become scarcer in the U.S., woodpeckers must compete with other species for more and more limited resources. But hopefully, by participating in the Woodpecker Cavity Cam project, citizen scientists can keep contributing to research on woodpecker nesting ecology and the importance of savanna sites, which in turn will help with restoration and preservation efforts for these rare habitats.
McCormick, James R.; Conner, Richard N.; Saenz, Daniel; Burt, D. Brent. 2004. Evidence of Red-cockaded Woodpecker nestling displacement by southern flying squirrels. Bulletin of the Texas Ornithological Society 37(1):8-9. See also Loeb, Susan C. 1993. Use and Selection of Red-Cockaded Woodpecker Cavities by Southern Flying Squirrels. Journal of Wildlife Management 57 (2): 329-353.
Ingold, D. J.1989a.Nesting phenology and competition for nest sites among Red-headed and Red-bellied Woodpeckers and European Starlings. Auk 106: 209-217. See also Reller, A. W. (1972). Aspects of behavioral ecology of Red-headed and Red-bellied woodpeckers. American Midland Naturalist 88: 270–290.