American Redstarts (Setophaga ruticilla) usurp Cerulean Warbler (Setophaga cerulea) nest in Southern Indiana

Documented observations of interspecific nest usurpation are rare and have been observed mostly in cavity-nesting species, where cavities are limiting and competition for them can be strong. We report one of the few known instances of interspecific nest usurpation in the family Parulidae (North American wood-warblers) between the Cerulean Warbler (Setophaga cerulea) and American Redstart (Setophaga ruticilla). During May and June 2016, we observed a female American Redstart usurp and successfully fledge at least one of its young from a nest built by a female Cerulean Warbler in Yellowwood State Forest, Brown County, Indiana. Based on our field observations, we provide information on nest chronology and describe American Redstart adult behaviors at the usurped nest. We hypothesize that this instance of interspecific nest usurpation may have been a result of high local breeding densities of both Cerulean Warblers and American Redstarts in our study area.