Charles R. Brown, professor of biological sciences, has received a five-year, $148,000 grant from the National Science Foundation for his continuing studies on the social behavior of cliff swallows in western Nebraska. Brown has studied cliff swallows for 34 years. The NSF grant will support his research on how climate-driven selection on group size varies in different years and can cause a range of colony sizes documented within the species’ natural habitat.
Brown’s paper “Ectoparasitism shortens the breeding season in a colonial bird” was published in the journal Royal Society Open Science in February 2015. The research reports the first evidence that blood-sucking parasites alter the breeding cycle in their bird hosts by shortening the amount of time birds can nest in the summer. Birds that attempt to nest later in the season often fail because parasite numbers increase over time.
“Over a 30-year period, we’ve fumigated colonies of cliff swallows to remove their parasites, and the birds responded by lengthening their breeding season and sometimes nesting twice in a summer,” Brown said.
His research showed the number of pairs initiating double nesting at a site increased each year for 27 years, suggesting natural selection for double nesting occurred when parasites were removed. According to Brown, the results indicate parasites have a previously unknown but major effect on their hosts.