Survivorship, habitat use, and movements for two species of mature forest birds

摘要: Habitat quality on the breeding grounds has been typically evaluated by investigating patterns in nesting success, while events that occur following fledging have largely ignored. However, one especially overlooked aspect of ground is how habitat affects post-fledging survival, which can be very low and greatly influence population recruitment. In this study, we estimated survival rates, identified features selected fledglings, then extent to selection other biological factors influenced survivorship fledgling Ovenbirds (Seiurus aurocapillus) Worm-eating Warblers (Helmitheros vermivorum). From 2004-2007, radio-tagged recorded daily locations 51 60 Warbler fledglings southeast Ohio, USA. We compared vegetation structure between actual random using a chi-squared analysis. For each species separately, known fate models program MARK were used generate estimates evaluate covariates. Post-fledging rates similar for two 65% 67% Warblers. Overall, both actively habitats characterized 32 dense contained 40-60% more woody stems understory locations. Moreover, use actually promoted survival. Fledgling condition at time radio-tagging also was positively related during period. Conservation strategies improved taking into account requirements. Although riparian thickets tree-fall gaps within some forests may provide abundant habitat, lack necessary maximize these cases, managers should consider creating suitable habitat. Introduction ecology North American songbirds focus numerous studies, ecological information concerning life cycle stages remains surprisingly incomplete. fact, basic parameters (i.e., survivorship, use) period are just beginning understood species, despite evidence suggesting juvenile play important roles demography (Anders & Marshall 2005; Yackell Adams et al. 2007). migratory generally spans 2-3 months with from nest lasting until initiation fall migration. Our poor understanding results primarily difficulty associated collecting data birds phase when they furtive do not broadcast their presence through song. Nevertheless, recent technological advances allowed miniaturization radio-transmitters, thereby permitting researchers track bird’s movement, 33 use, survivorship. Despite increased interest an unprecedented number studies over last 10-15 years, much research America focused single Wood Thrush (Hylocichla mustelina; Anders 1997; Powell 2000; Vega Rivera 1998), few exist majority forest songbirds. Traditionally, assumed similar, but empirical show necessarily case 1998). needs might expected change across annual given need meet reproductive requirements site selection, mate acquisition, courtship, nestling provisioning), whereas non-breeding birds, including Indeed, differences postfledging periods well documented Ruffed Grouse (Bonasa umbellus), frequently move broods areas young aspen stands (Thompson Dessecker 1997) alder (Rusch 2000). Similarly, there strong mature The most forest-breeding exhibit same