Social behavior in birds and other animals is remarkably diverse, ranging from short-term interactions (like pollination or predation) to lifetime associations (like mutualism or competition) and can be between members of the same species or span many different species. Field work on the red-headed woodpecker project allows us the opportunity to see many different interactions as we conduct our work—both between individual red-headed woodpeckers and among these individuals and other bird species that nest at Cedar Creek. A number of interactions between red-headed woodpeckers and other species over the last two field seasons have been particularly notable to those of us working on this project and we are lucky enough to be able to share them here.
It came to our attention during the 2018 breeding season that a pair of red-headed woodpeckers appeared to be competing with a pair of European starlings (also known as Common starlings) for a nest cavity. We observed a red-headed woodpecker tossing grass out of the cavity, and subsequently recorded red-headed woodpecker eggs inside about a week later. Shortly thereafter, this woodpecker nest was usurped by starlings, who nested there successfully. Interestingly, we also observed a pair of red-headed woodpeckers and a pair of starlings nesting in the same oak snag—the starling nest was located about 6 feet above the woodpecker nest, apartment-style. The birds seemingly ignored each other, perhaps content to share the tree, rather than compete.
At the start of our 2019 breeding season, we found a Northern flicker nesting in a cavity that had been excavated and used by red-headed woodpeckers the previous breeding season. Shortly after we discovered this flicker nest we observed a pair of red-headed woodpeckers excavating a new cavity in the same tree about 2 feet away from the flicker nest. Another case of apartment-style living for a red-headed woodpecker and another species.
We kept an eye on this flicker nest while doing nest checks for red-headed woodpeckers and we're happy to report that these flickers successfully fledged. We were even lucky enough to see them being fed by a parent days after fledging the nest. Unfortunately the red-headed woodpecker nest failed in late June. We documented two red-headed woodpecker eggs and the adults incubating these eggs, but eventually the eggs disappeared from the nest. We don't know whether the removal of the eggs was caused by a predator or the parents.
In another interesting case not far from the flicker-red-headed woodpecker apartment, Siah St. Clair, one of our citizen science volunteers, documented multiple and very aggressive exchanges between an Eastern kingbird and a red-headed woodpecker. In the photo below, the woodpecker is on the trunk of the tree where the kingbird's nest is located. This tree is about 25 meters from the woodpecker's nest tree.
According to Siah, the whole episode lasted less than 4 minutes, during which time the red-headed woodpecker partially destroyed the kingbird's nest, despite both members of the kingbird pair trying to attack the woodpecker, who was eventually driven off by the kingbirds. The photo below shows the kingbird nest with a hole in the middle of it. The picture below shows two white objects that could be eggs. One of the kingbirds was incubating the day after the attack, so it's likely that the woodpecker didn't entirely destroy the nest. We don't know what caused this interaction—whether the woodpecker was defending his nesting territory or perhaps going after the kingbird eggs for a protein-rich meal.
It's not entirely clear why we see such diversity in social behavior, why and when birds choose to be social, or how individual birds mediate interactions with members of different species in order to co-exist. We'll keep observing and sharing these curious stories here.