Preferences for Nesting Sites in Prothontary Warblers (Protonotaria citrea)

The Prothonotary warbler (Protonotaria citrea) is a secondary cavity-nesting species found in bottomland forests throughout the eastern half of the United States. Although not classified as a threatened species, its population has been in decline over the past few decades. This decline is mainly due to agriculture and wetland drainage causing a decrease in habitat and food sources and an increase in predation and brood parasitism by raccoons (Procyon lotor) and brown-headed cowbirds (Molothrus ater). Interspecific competition for nesting sites and food with Carolina wrens (Thryothorus ludovicianus) and house wrens (Troglodytes aedon) also has contributed to their decline. Because of their close relationship with hydrological processes and sensitivity to ecological change, Prothonotary warblers can serve as an important indicator species to determine the health of the ecosystems they reside in. Conservation of this species focused on improving site fidelity for nesting also often inadvertently improves the overall quality of its habitat. Previous studies have had success with installing artificial nesting boxes to increase the number of individuals nesting in the area. The purpose of our study is to determine the ideal nesting sites for Prothonotary warblers to guide the placement of artificial nesting boxes in the bottomland forests in Springfield, Illinois.  Nesting boxes placed within 5 m from a regular water source, 1.5 to 1.7 m above the ground, and spaced 25 to 40 m apart from each other were used more readily by Prothonotary warblers.  Siting that discourages house wrens, Carolina wrens, raccoons, and brown-headed cowbirds is also desired.