Meeting Abstract
Spring migratory movements of obligate migrants are consistent, both in terms of where animals travel to and from, as well as when these movements occur. In contrast, facultative migrants have unpredictable migrations that vary both spatially and temporally. While recent studies have examined the environmental cues used to initiate facultative migration, it is still unclear what information facultative migrants use to terminate their migratory movements. We examined whether the addition of a social partner influences the termination of migratory behavior in pine siskins (Spinus pinus), a nomadic, irruptive migrant. We videotaped birds in late spring to assess their nocturnal activity as an indicator of migratory status (migratory/non-migratory) and then either paired birds that differed in their migratory status or left migratory and non-migratory birds unpaired as controls. We videotaped birds immediately after pairing and again 10 days later. We also measured body parameters that are indicative of migratory preparations when birds were initially assigned a treatment and at the end of the experiment. Migratory and non-migratory control birds did not change their nocturnal activity levels during the experiment, but the paired migratory birds decreased their nocturnal activity. The decrease in nocturnal activity in the paired migratory birds was evident on the first night after pairing. Paired migratory birds also decreased their mass and fat deposits. These results suggest that social pairing can quickly synchronize not only migratory behavior, but also physiology. This would increase group cohesiveness and the likelihood that individuals that migrate together would ultimately terminate movements at the same time, which may ultimately facilitate the transition to breeding.
