SURVIVAL OF FLEDGLING HOODED WARBLERS (WILSONIA CITRINA) IN SMALL AND LARGE FOREST FRAGMENTS

Abstract

Studies on the effects of forest fragmentation on the reproductive ecology of forest songbirds have focused almost exclusively on the egg and nestling stages. Little is known about survival or habitat use of fledglings in their first weeks out of the nest. We radiotracked adult Hooded Warblers (Wilsonia citrina) attending fledglings from large (>150-ha) and small (<30-ha) forest fragments during 2002 and 2003. Mark–recapture models were used to assess the effects of forest-fragment size and age of the attending adult on the survival of young. We also examined the structure of nesting- versus postfledging-habitat used by fledglings. Only 19% of fledgling Hooded Warblers survived the 28-day fledgling period prior to independence, and fledglings' daily survival probability was lowest in the first four days after they left the nest (1–2 days postfledging: 0.72; 3–4 days postfledging: 0.69). Fledgling survival did not differ between large and small forest fragments. Large fragments were more likely to contain older adults, and age of parent had a positive influence on fledgling survival, independent of fragment size. As in many other studies, overall productivity was higher within larger fragments; this was largely attributable to differences in number fledged rather than fledgling survival. Habitat used by fledglings was more structurally complex than habitat at nest sites, which indicates that fledglings may seek habitat with high cover to avoid predation. Fledgling survival was much lower than estimates used in demographic models, which suggests that for many species, these models may need re-evaluation. Supervivencia de Volantones de Wilsonia citrina en Fragmentos de Bosque Pequeños y Grandes