Familiar Common Nighthawk, pictured above, is in steep decline. Reasons for the falloff aren’t certain. A drop in populations of the flying insects the bird eats is a likely factor, as is the loss of nesting habitat, on the ground in rural areas and on flat, gravel roofs in cities.
Curious whether urban American Crows may also be playing a role, researchers Steven C. Latta and Krista N. Latta placed artificial nests atop buildings at the University of Wyoming, in Laramie, and on the ground in a pristine mixed-grass prairie, and monitored them with motion-activated cameras.
None of the rural nests lost eggs, while almost 45 percent of the roof nests did. In each case where a culprit could be identified, it was one or more crows. “While experimental predation rates may not represent actual levels of predation on natural nests,” conclude the researchers, the results suggest that urban crows may be an “important contributor to declining populations of Common Nighthawks.”
Steven Latta is director of conservation and field research at the National Aviary, in Pittsburgh. Krista Latta is in the Department of Veterinary Sciences, University of Wyoming, in Laramie. The researchers described their study in the September 2015 issue of the Wilson Journal of Ornithology, the quarterly journal of the Wilson Society for Ornithology.
Read the paper
Steven C. Latta and Krista N. Latta (2015) Do Urban American Crows (Corvus brachyrhynchos) Contribute to Population Declines of the Common Nighthawk (Chordeiles minor)? Wilson Journal of Ornithology, 127 (3): 528-533.
A version of this article appeared in the August 2016 issue of BirdWatching.
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