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Most work on the effects of land-cover change on tropical birds has focused on forest-interior birds because these species are assumed to be the most severely affected by forest loss. However, even species that use human-altered habitat types may be severely affected by forest loss. White-throated Robins (Turdus assimilis) frequently nest in coffee and pasture in southern Costa Rica, although several lines of evidence suggest the species could not exist solely in agricultural habitat. We used radio-telemetry to examine the area and proportion of different habitat types used by adult White-throated Robins. Mean area of use for the tracking period was 0.26 km² and varied from 0.07 to 0.58 km². No robins had areas of use solely in either primary forest or agricultural cover, although individuals were initially captured in both primary forest and a coffee plantation. All areas of use contained some forest, pasture, and coffee or regenerating forest. The mean percentages of the habitat types used by the birds were fairly equal with 30% forest, 33% pasture, and 38% coffee or regenerating forest. Our results, combined with other evidence, indicate that the White-throated Robin uses multiple habitat types but that it may require some threshold level of forest to sustain viable populations.
