The conservation implications of site fidelity: A case study involving nearctic-neotropical migrant songbirds wintering in a Costa Rican mangrove

Abstract

The ecological and conservation implications of site fidelity among nearctic-neotropical migrant songbirds wintering in a Costa Rican mangrove forest were examined. During two boreal winters, 168 (24%) of 700 individuals were captured more than once within winter seasons. Among these, birds from six of 15 migratory species were re-trapped. The vast majority of recaptures were either prothonotary warblers Protonotaria citrea or northern waterthrush Seiurus noveboracensis. Between winters, only prothonotary warblers, northern waterthrush and yellow warblers Dendroica petechia were recaptured, with 55 (16%) of 336 individuals originally caught in winter 1990–1991 being re-trapped in winter 1991–1992. Examination of body condition indices revealed no significant difference between prothonotary warblers which returned the second year and those which did not, but northern waterthrush which returned for a second winter had significantly greater body mass and body condition indices than those which did not return. Although we detected no differences in between-year recapture rate for migrants at this site, differences in site fidelity may exist and be an important conservation issue for nearctic-neotropical migrants. Those species with high levels of site fidelity between years may be less adaptable to habitat degradation and loss. As distance between patches of suitable habitat grows with increasing deforestation of tropical zones, even returning to the same region may not lead to the discovery of suitable habitat. Migratory species such as these may be the most vulnerable to population declines in the face of losses on their wintering grounds.