Biologist Caldwell Hahn at the Patuxent Wildlife Research Center in Maryland is trying to find out which songbirds raise the most cowbirds. She could have tediously observed the nests of hundreds of songbirds to see which species were targeted most often. But, she says, she realized the cowbirds would pick up lice that infest songbird feathers and that perhaps she could examine lice on songbirds and cowbirds to identify those species the cowbirds victimize. She and her colleagues caught 797 songbirds of 30 species and 249 cowbirds. They placed each bird in a jar containing ethyl acetate, which kills the bugs but not the birds.
Avian lice are species-specific.
To birds, lice are an itchy annoyance. But to biologists Caldwell Hahn and P. C. Osenton of the Patuxent Wildlife Research Center and R. D. Price of the University of Minnesota, they're a source of inspiration. Recently, the trio used the tiny parasites to track the incursions of a much larger parasite, the Brown-headed Cowbird. Female cowbirds lay their eggs in other birds' nests, where the greedy cowbird babies outcompete their foster siblings. Scientists think these habits may be contributing to population declines in some songbird species.