WOOD THRUSH POSTFLEDGING MOVEMENTS AND HABITAT USE IN NORTHERN VIRGINIA

We monitored 42 radio-tagged fledgling Wood Thrushes (Hylocichla muste lina) to investigate movement and habitat use during the postfledging period. Fledglings' mean (+/- SE) age at dispersal from the natal site s was 32.5 +/- 0.6 days post hatching. First dispersal sites were loca ted 1.5 +/- 0.3 km from the natal site. All young joined flocks of juv eniles, except three birds that remained solitary. Sixteen birds staye d at the first dispersal site until departure on migration, whereas ni ne visited additional dispersal sites. On 40 occasions, 15 fledglings moved up to 6 km from their dispersal sites. Before late August, 96.7% of fledglings' locations occurred in: (1) second growth scrub/deciduo us sapling sites located along forest borders and abandoned farms (59. 4%), (2) gypsy moth (Lymantria dispar) damaged deciduous forest (24.4% ), and (3) Virginia pine (Pinus virginianus) forest with heavy deciduo us understory (12.8%). Fruiting trees and shrubs used as food sources by juveniles fruit earlier in these habitats. After late August, an in creased number of fledgling locations (14.1%) occurred in mature decid uous or mixed forest, possibly tracking the later fruiting cycles of u nderstory plants in these habitats. Twenty-four of 33 fledglings left the study area in September. Mean age at departure was 81 +/- 5 days p ost hatching. We suggest that postfledging movements in Wood Thrushes are keyed by the availability of food resources and the presence of co nspecifics, although other factors may play a role. We conclude that s uccessful conservation of migratory species requires protection of hab itats used during the postfledging period as well as those used during the nesting portion of the life cycle.