SI2015-C-5: “Post-breeding movements of a migratory songbird reveal dramatic differences between adults and fledglings” – Zoe J. Crysler

Post-breeding dispersal is a crucial yet challenging period for migratory birds. It is poorly understood due to difficulties in tracking cryptic, and sometimes far ranging birds preparing for migration. Island breeding birds are ideal candidates for breeding ground studies because their populations are clearly demarcated and movement is confined. The Ipswich Sparrow (Passerculus sandwichensis princeps), a subspecies of the Savannah Sparrow, is a species of special concern, that breeds exclusively on Sable Island, Nova Scotia. Automated digital telemetry was used to assess the dispersal and movement behaviour of adult and fledgling Ipswich Sparrows on their breeding grounds. Here we seek to answer the following questions with regard to the various dispersal hypotheses: 1) does use of primary sites vary by age or body condition; 2) does movement behaviour (direction of movement and distance of uninterrupted flights) change as migration approaches; and 3) does the type of behaviour (movement vs. stationary) change with time of day or location. We found that adult and fledgling breeding ground dispersal is distinctly different. Adults were present at primary sites for a significantly higher proportion of time and were not detected at any other location on the breeding grounds suggesting very little dispersal. Alternately, fledglings appear to use primary sites much less frequently, and have numerous broad scale movements dependent on approaching migration initiation date.

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