Composition and Microclimate of Prothonotary Warbler Nests

During studies of Prothonotary Warblers (Protonotaria citrea) nesting in artificial nest boxes, we made two observations suggesting that physical environment affects nesting by this species. In the present analyses, we examine the composition and microclimate of these nests and ask the following questions: (1) Does their use of moist bryophytes significantly modify the microclimate of the nest cavity? (2) Does ambient temperature affect nest cavity selection by Prothonotary Warblers? We studied Prothonotary Warbler breeding activity in 250 wooden nest boxes in tidal swamps in and near Presquile National Wildlife Refuge on the James River near Hopewell, Virginia, (37 degree 20'N, 77 degree 15'W), from 1987 through 1991.