THE CONSERVATION IMPLICATIONS OF SITE FIDELITY - A CASE-STUDY INVOLVING NEARCTIC-NEOTROPICAL MIGRANT SONGBIRDS WINTERING IN A COSTA-RICAN MANGROVE

The ecological and conservation implications of site fidelity among ne arctic-neotropical migrant songbirds wintering in a Costa Rican mangro ve forest were examined. During two boreal winters, 168 (24%) of 700 i ndividuals were captured more than once within winter seasons. Among t hese, 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 winter s, only prothonotary warblers, northern water thrush and yellow warble rs Dendroica petechia were recaptured, with 55 (16%) of 336 individual s originally caught in winter 1990-91 being re-trapped in winter 1991- 92. Examination of body condition indices revealed no significant diff erence between prothonotary warblers which returned the second year an d those which did not, but northern waterthrush which returned for a s econd winter had significantly greater body mass and body condition in dices than those which did not return. Although we detected no differe nces in between-year recapture rate for migrants at this site, differe nces 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 degradati on and loss. As distance between patches of suitable habitat grows wit h increasing deforestation of tropical zones, even returning to the sa me region may not lead to the discovery of suitable habitat. Migratory species such as these may be the most vulnerable to population declin es in the face of losses on their wintering grounds. (C) 1996 Elsevier Science Ltd