Factors Governing Habitat Selection by Prothonotary Warblers: Field Tests of the Fretwell‐Lucas Models

Abstract

The ecological and evolutionary ramifications of habitat selection for the population dynamics of Prothonotary Warblers (Protonotaria citrea) were examined by evaluating specific factors affecting choice of habitat by the warblers, and testing the predictions of habitat selection theories proposed by Fretwell and Lucas (1970). Seven study plots were established along the Tennessee River in west—central Tennessee between 1987 and 1989. Each plot consisted of 80 nest boxes in a 20 column $\times$ 4 row grid, with one row placed along shoreline over standing water (flooded habitat), and three parallel rows placed inland at 35—m intervals (dry habitat). Flooded and dry habitats differed in vegetative structure and species composition, and flooded habitat contained more natural nest sites, higher arthropod abundances, and fewer species competing for nest sites than did dry habitats. Warblers settled preferentially in flooded habitat, where breeding density was higher than in dry habitat. When predation effects were excluded, birds in flooded habitat fledged more young per nest and made more nesting attempts than did birds in dry areas. With predation included, no significant differences in breeding success in the two habitats were found. Distribution of breeding warblers across wet and dry habitats followed the “ideal dominance” model of Fretwell and Lucas (1970), with older and larger males excluding younger and smaller ones from flooded areas. Territoriality in Prothonotary Warblers apparently serves to limit breeding density and to maximize breeding success within preferred habitat.