Stopover ecology and habitat selection of juvenile Swainson's thrushes during fall migration along the northern California coast

I investigated stopover habitat selection of juvenile Swainson's Thrushes (Catharus ustulatus) during fall migration at the Lanphere Dunes along the Northern California Coast. For 26 birds captured and radio-tracked in 2002 and 2003, the average minimum length of stay was 8.9 ± 1.0 days. For 20 of the birds with a sufficient number of locations, the average home range size was 1.9 ± 0.3 ha. Thrushes showed no overall pattern of selection for forest type within the study area or for forest type used inside their home range. Fat and lean birds selected forest types similarly within the study area and their home ranges. However, locations occupied by lean birds had twice as much huckleberry shrub cover and 1.3 times more concealment than locations occupied by fat birds. Overall, there were 2.5 times more huckleberries at occupied than random locations, and lean birds had 2.9 times more berries than fat birds at occupied locations. Fecal analyses confirmed that huckleberries were a commonly consumed food. However, thrushes also ate arthropods and wax myrtle bracteoles. The overall lack of forest type selection coupled with differences in selection for cover and fruit abundance between fat and lean birds suggests that fat level may influence microsite selection.