Meeting Abstract
Facultative migration is characterized by unpredictable, highly variable patterns of movement that vary in both direction and timing. Studies suggest a decline in food availability can trigger migration in an attempt to locate more favorable habitat. Many facultative migrants feed on conifer seeds, which vary both spatially and temporally in abundance. Since social information can increase foraging success in unpredictable habitats, facultative migrants may utilize information gained from conspecifics about local conditions when migrating in response to a reduction in food. Pine siskins (Spinus pinus) are a nomadic, irruptive migratory finch and exhibit behavioral and physiological responses to declining food availability that suggests a migratory transition. To examine the effect of social environment on response to food availability, birds received either ad libitum food (control) or a restricted diet and were housed such that they could either hear only birds experiencing the same food treatment as themselves or hear birds from both food treatments. Birds in the all-food restricted group had significantly higher daytime activity levels compared to birds in the all-control group. Both control and food restricted birds in the mixed-treatment group had activity levels that were intermediate between the all-control and all-food restricted groups. Birds in the all-food restricted group gained more weight post-restriction compared to food restricted birds in the mixed-treatment group. Unexpectedly, circulating corticosterone levels increased in all groups during food restriction. These results suggest pine siskins integrate vocally-communicated information gained from other group members when responding to declining resources, which may have population-level effects across a dynamic environmental landscape.
