Rapid adoption of nestboxes by Prothonotary Warblers (Protonotaria citrea) in mesic deciduous forest

Breeding territory selection in Prothonotary Warblers (Protonotaria citrea (Boddaert, 1783)) is thought to hinge on standing water, with a strong preference for low-lying areas prone to seasonal flooding. However, we have observed this species nesting in much drier areas than previously reported. We recently initiated a study of the Carolina Wren (Thryothorus ludovicianus (Latham, 1790)) using wooden nest boxes, and nearly 60% of all nests produced in these boxes during the initial study year were produced by Prothonotary Warblers, despite this species being absent from our field site during the year preceding nest-box availability. Most nests were produced in dense, closed-canopy forest with a thick shrub layer >100 m from any water body. There was no difference in the mean distance from water between nests of the Prothonotary Warbler and those of the Carolina Wren, a habitat generalist that does not nest over water. We then observed a 60% increase in the number of Prothonotary Warbler nests the following year, along with significant increases in breeding productivity. Although they nested on sites that they are not thought to prefer, our observations suggest that Prothonotary Warblers may nest in drier areas than usual if appropriate nest cavities are provided.