![]() Of the 121 Big/Big pairs, 74% contained only a bluebird nest while 26% contained both a bluebird nest and the successful nest of a chickadee or nuthatch. We had 100 “Big/Small” box pairs with a successful bluebird nest. Photo © Douglas Wipf Bluebirds Exclude Their Small NeighborsĬombining two years of data, we had a total of 121 “Big/Big” pairs with a successful bluebird nest. Black-capped Chickadee Nest Boxīlack-capped Chickadees can nest in boxes with entrance holes as small as 1 1/8 inches in diameter. Finally, if bluebirds guard all usable nest boxes in a small area (the Greedy Bluebird scenario), we would expect to find high occupation of “Big/Small” box pairs by nuthatches and chickadees and low occupation by these species of “Big/Big” box pairs. If, however, bluebirds simply defend their own nest cavity (the Tolerant Bluebird scenario), we would expect to find similar (and high) occupancy by nuthatches and chickadees in box pairs of either type that contained bluebirds. If Eastern Bluebirds are intolerant of subordinate cavity-nesters breeding nearby (the Intolerant Bluebird scenario), we would expect to find similar (and low) occupancy by nuthatches and chickadees in box pairs of either type that contained bluebirds. Eastern Bluebirds Scoping Out A Nest BoxĮastern Bluebirds can nest in boxes with holes as small as 1 1/2 inches in diameter. ![]() The larger holes could accommodate bluebirds, chickadees, and nuthatches, but the smaller holes effectively excluded bluebirds. Some of the pairs consisted of two identical nest boxes (both with 1.5-inch entrance holes) while other pairs consisted of one box with a 1.5-inch entrance hole (“Big”) and the other with a 1-inch entrance hole (“Small”). Consequently, we had two treatments that would allow us to narrow down what was going on. But would bluebirds allow smaller species, specifically Carolina Chickadees and Brown-headed Nuthatches, to use the box that they were not using themselves? Of course, the absence of a second species nesting beside a bluebird could be due to any number of factors. Because Eastern Bluebirds are territorial, there was no way that two pairs of bluebirds would nest side-by-side. We installed identical nest boxes in pairs 10 meters (~33 feet) apart. My students and I at Davidson College in North Carolina decided to test this. How then, can one assist smaller birds like chickadees and Brown-headed Nuthatches if they are continually facing competition from larger birds like bluebirds? Could paired boxes ensure the coexistence of chickadees and bluebirds the same way that paired boxes allow bluebirds and Tree Swallows to nest peacefully side by side? On the Tolerance of Bluebirds Body size is often a fairly reliable predictor of interspecific dominance, so it seems likely that larger species (Tree Swallows, bluebirds) might be able to monopolize boxes that smaller species could potentially use. By installing boxes in pairs (close enough that both boxes are unlikely to fill with Tree Swallows), nest box monitors can ensure that their beloved bluebirds have somewhere to nest.īut what about cases where the bluebird, aided by its bigger body size, is the dominant species? In eastern North America, a standard bluebird box is likely to attract a variety of potential residents, many of them smaller than bluebirds. Indeed, fans of Eastern Bluebirds in the upper Midwest long ago began to provide paired nest boxes to ensure that bluebirds were able to coexist with the more aggressive Tree Swallows. Perhaps the simplest way to reduce such competition is to provide multiple nest boxes. This doesn’t mean that there is nothing we can do as nest box monitors to reduce nest site competition. Tree Swallows On The WatchĪdult Tree Swallows will compete with Eastern Bluebirds for nest boxes. This is a natural part of the avian life cycle, and one that humans often have little ability to control. If a dominant species is simply able to monopolize the area around a nest box, subordinate species may not even attempt nesting. ![]() But often nest site competition is so subtle it’s practically invisible (to us). Sometimes one can observe chases and even violence. In particular, many nest box landlords can be disheartened or even upset when multiple species compete for a nest box: it’s not always a pretty sight. However, sometimes nature can be a bit red in tooth and claw. Watching cavity-nesting birds build nests and care for young in our nest boxes is deeply satisfying. Mark Stanback, Professor of Biology, Davidson College A Tale of Two Boxes: When Pairing Doesn’t Promote Peace Photo ©
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |