| While wintering and breeding are geographically separated in migratory bird species, a growing body of evidence suggests that winter events and winter location may have effects that carry over and impact aspects of the breeding season. In this study, I investigated the effects of a winter event (prealternate moult) and winter location on breeding success in a short-distance migrant, the Ipswich Sparrow (Passerculus sandwichensis princeps). Ipswich Sparrows, a subspecies of Savannah Sparrow, breed almost exclusively on Sable Island, Nova Scotia; and winter along the Atlantic coast from Nova Scotia to Florida.;My second goal was to determine if aspects of winter location impacted the breeding season in Ipswich Sparrows. I used hydrogen stable isotope analysis to determine wintering latitude and carbon and nitrogen stable isotope analysis to infer aspects of winter diet. My sample of sparrows wintered mainly in the northern and middle portions of the range. Males also wintered further north than females, and winter location impacted reproductive success in both sexes. Males that wintered in the northern part of the wintering range were in better condition, established territories earlier, and tended to produce heavier nestlings than those that wintered further south. Conversely, females that wintered towards the southern part of the wintering range had earlier first egg dates than those wintering further north. Individuals wintering further south relied mainly on a diet of C4 plants, while those wintering further north incorporated C3 plants in their diet. Nitrogen isotope ratios were not useful in determining trophic level, but were related to condition and therefore may provide information regarding quality of winter habitat.;My first goal was to describe the incidence, timing and extent of the partial winter (prealternate) moult of Ipswich Sparrows, and determine if relationships existed between prealternate moult and breeding performance or winter location. Prealtemate moult only occurred in 25% of Ipswich Sparrows and was mainly restricted to tertials, rectrices and back feathers. Approximately half of the individuals that moulted were actively moulting during the breeding season; and stable isotope evidence suggests that some individuals moult during migration. There was no relationship between the incidence of prealternate moult and breeding performance, nor was prealternate moult related to winter location. My results suggest that prealternate moult is a relatively low-cost activity for Ipswich Sparrows, and that it may function to replace plumage degraded by sunlight. |
