Movement ecology of songbirds during migratory periods

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Migratory birds undertake long-distance movements yearly between over-wintering and breeding areas. During these migrations they must stopover in often unfamiliar landscapes to rest and refuel for subsequent flights. These stopover periods are important to the life history of the individuals since a considerable portion of yearly mortality likely occurs during them, and choices made may influence subsequent survival or breeding success. Because of the small size of many passerine birds (they are difficult to track through space and time), there is little known about these behaviours at the scales required. My lab has developed an automated system of VHF telemetry (motus.org) that can be used to track small passerine birds. In previous work we have shown that during stopover, individuals may move considerable distances over landscapes during the fall migratory period. Here, we propose to extend our work on stopover to the spring period (by marking birds on the wintering grounds), to initiate additional demographic studies during the overwintering period, and to experimentally test two hypotheses regarding the function of regional-scale movements in fall. The results will help elucidate the function of these movements, and provide insight into their demographic consequences.