FLEDGING AND MIGRATION OF JUVENILE BALD EAGLES FROM GLACIER NATIONAL-PARK, MONTANA

During 1985-95, we documented fledging, migration, and subsequent loca tions of juvenile bald eagles (Haliaeetus leucocephalus) from Glacier National Park (GNP), Montana. The median fledging date was 1 August (N = 29). We radiotagged 11 fledglings, nine of which also received wing markers. The median date of migration from natal areas was 13 Septemb er (N = 15). The interval between fledging and migration varied from 3 2 to 70 d (median = 42 d, N = 15). Juveniles appeared to migrate alone , joining other eagles at foraging sites. GNP adults remained on their nesting territories when juveniles departed. One juvenile wintered 13 0 km from GNP. Others migrated as far as 1000 km. Six migrated to sout hern Montana, Idaho, Wyoming, and California. Three moved west to Wash ington or British Columbia. Two juveniles from the 1988 Lake McDonald nest migrated separately to the Pacific Coast. By 1991, one Lake McDon ald adult had been replaced; the juvenile produced that year migrated south to Idaho. This contrast suggests that juveniles inherited distin ct migration direction ''programs'' from different parents. Early autu mn migration departures of GNP juveniles also may be genetically deter mined; we found no evidence that they remained locally to feed on autu mn spawning runs of kokanee salmon (Oncorhynchus nerka) in GNP. At lea st 10 of the 11 radio-tagged juveniles survived their first winter. Du ring spring migration, four juveniles passed through or near GNP. Nine summering sites or last known spring locations were in Alberta or Bri tish Columbia, Canada. There is no evidence to date of marked juvenile s returning to breed in GNP natal areas.