Nest desertion by blue-gray gnatcatchers in association with brown-headed cowbird parasitism

The blue-gray gnatcatcher, 'Polioptila caerulea,' deserts its nest in response to parasitism by the brown-headed cowbird, 'Molothrus ater.' Nest desertion seems to be an effective strategy to avoid parasitism and increase fitness. Deserting gnatcatchers usually obtain clutches free from cowbird disturbance. However, nest desertion response was inconsistent and the factor that triggers it is unclear.