Habitat selection and habitat-specific survival of fledgling ovenbirds (Seiurus aurocapilla)

Patterns of habitat use by some passerines change after the young leave the nest, and thus our understanding of habitat selection derived from counts of singing males earlier in the nesting cycle may not adequately represent the breeding habitat requirements of these species. Post-fledging changes in habitat use may have important conservation implications if the survival of fledglings is affected by characteristics of the habitat; however, there have been relatively few systematic studies of the post-fledging ecology of forest passerines and, of these, even fewer have incorporated analyses of the relationship between habitat characteristics and fledgling survival. We studied the post-fledging habitat selection and survival of ovenbirds Seiurus aurocapilla in northern New Hampshire, USA during two breeding seasons using radio telemetry. Habitat at sites used by radio-marked fledgling ovenbirds was characterized by fewer large trees and greater vertical structure 0-3 m above ground than ovenbird nest sites. Similarly, habitat at sites used by fledgling ovenbirds was characterized by fewer large trees and greater vertical structure than unused sites. Most (80%) of the 15 mortalities that we observed were due to predation. Nine (70%) of these occurred within the first 3 days of fledging, resulting in a significant drop in survival during this period. Fledgling survival increased significantly with increased vegetation structure. Our observations that fledgling ovenbirds are selective in their habitat use, that they select different habitat features than adult ovenbirds select for nesting and that fledgling survival is positively associated with these habitat features suggest that the use of habitat models based on counts of singing males before fledging does not adequately represent the habitat needs of this species. Conceivably, mortality during the post-fledging period could limit recruitment to levels insufficient to maintain the viability of ovenbird population even if adequate nesting habitat were available.