ABSTRACT
Abstract. We used radiotelemetry and observations of color-banded birds in Costa Rica and Nicaragua to characterize the social system and foraging behavior of Golden-winged Warblers (Vermivora chrysoptera) at the nonbreeding grounds, and we assessed how these behaviors affected intraspecic spacing and home-range size. Golden-winged Warblers spent the majority of their time associating with mixed-species ocks composed of migrant and resident species. Males were territorial, responding aggressively to broadcast vocalizations and exhibiting a high degree of within-and among-season site delity. We rarely observed males ocking with other male Golden-winged Warblers, and there was little overlap of neighboring male home ranges. In contrast, female home ranges overlapped extensively with neighboring male home ranges. Home-range sizes did not differ between sexes but were larger in Costa Rica (8.77 ± 0.92 ha) than in Nicaragua (4.09 ± 1.30 ha). Home ranges were larger than reports of most
other migratory parulids, and we hypothesize that large home-range size and high propensity to join mixed-species ocks result from the species’ specialized foraging behaviors. The predominant foraging behavior involved probing hanging dead leaves and epiphytes for arthropods. Although this foraging strategy can be highly effective, it is noisy and reduces vigilance, which may explain the propensity for joining mixed-species ocks because group living can reduce predation risk. Our results indicate that the nonbreeding season behaviors of Golden-winged Warbler have important conservation implications because mixedspecies ocks can be disrupted by habitat loss and fragmentation, and because specialized foraging requirements, large home ranges, and territorial behavior reduce the potential density at which the species can occur.
