Territorial Exclusion by a Long-Distance Migrant Warbler in Jamaica: A Removal Experiment with American Redstarts (Setophaga ruticilla)

Abstract

To test whether male American Redstarts (Setophaga ruticilla) excluded conspe- cifics from selected habitats on their wintering grounds, we removed territorial individuals from four replicate sites in two different habitats in Jamaica, West Indies, and recorded territory shifts and new colonizations of the vacated areas. In total, 12 American Redstarts (nine after-hatch-year [AHY] or older males, two yearling [HY] males, and one female) were removed, and their vacated territories were re-occupied by 18 neighboring or newly-ap- pearing redstarts (five AHY males, four HY males and nine females). The re-occupation of the vacated areas supports the hypothesis that territoriality in this species acts to exclude conspecifics from certain winter habitat, and shows that American Redstarts compete with conspecifics for habitat in their winter grounds. Moreover, a statistically significant shift in sex composition following removal indicates that AHY males excluded females from mutually acceptable habitats. Such behavioral dominance, if confirmed, could help account for sexual habitat segregation during winter, and could result in differential winter survival rates between the sexes, thereby influencing population structure and regulation in this long- distance migrant. Received