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The costs and benefits associated with migration differ depending on individual decisions regarding the distance to migrate and where to winter. These decisions affect an individual's winter experience, which may in turn impact reproductive success the following breeding season. We investigated whether winter location influences performance on the breeding grounds in a short-distance migrant, the Ipswich Sparrow (Passerculus sandwichensis princeps Maynard, 1872), endemic to Sable Island, Nova Scotia, Canada. We used stable hydrogen isotope analysis to infer the winter location of individuals breeding on Sable Island, and investigated whether body condition, timing of breeding initiation, and number and condition of nestlings varied with winter location. Males wintered farther north than females, and males from the northern end of the wintering range were in better condition, established territories earlier, and tended to produce heavier nestlings than those wintering farther south. Conversely, females that wintered farther south had significantly earlier first egg dates than those that wintered farther north. The results of this study suggest that individual decisions about migration distance can impact reproductive success and that optimal winter locations differ between male and female Ipswich Sparrows. Les coûts et les bénéfices associés à la migration peuvent varier d'après les décisions individuelles faites concernant la distance de la migration et l'endroit de l'hivernage. Ces décisions affectent l'expérience individuelle pendant l'hiver qui, à son tour, a un impact sur le succès reproductif durant la saison de reproduction suivante. Nous examinons si le lieu de l'hivernage influence la performance sur les aires de reproduction chez un migrateur de courte distance, le bruant des prés (Passerculus sandwichensis princeps Maynard, 1872) endémique à l'île de Sable, Nouvelle-Écosse, Canada. Nous utilisons une analyse des isotopes stables d'hydrogène pour déduire le site d'hivernage des individus qui se reproduisent à l'île de Sable et recherchons si la condition corporelle, le calendrier du début de la reproduction et le nombre et la condition des petits au nid varient en fonction du lieu d'hivernage. Les mâles passent l'hiver plus au nord que les femelles et les mâles provenant de la partie plus nordique de l'aire d'hivernage sont en meilleure condition, établissent leur territoire plus tôt et tendent à produire des petits au nid plus lourds que ceux qui hivernent plus au sud. À l'inverse, les femelles qui hivernent plus au sud produisent des premières pontes significativement plus hâtives que celles qui hivernent plus au nord. Les résultats de notre étude indiquent que les décisions individuelles concernant la distance de migration peuvent affecter le succès de la reproduction et que les sites optimaux d'hivernage ne sont pas les mêmes chez les mâles et les femelles du bruant des prés. [ABSTRACT FROM AUTHOR]

The Ipswich Sparrow (Passerculus sandwichensis princeps) population on Sable Island, Nova Scotia, has been designated as "vulnerable" by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). Previous surveys of this population during the nesting season have varied in coverage and the rigour of statistical-survey design. In 1998 we surveyed the population using a stratified random-transect design. Estimated total numbers (±SE) were obtained along with confidence intervals calculated using bootstrap methods. The precision of our survey estimates would permit detection of population differences on the order of 20%. Higher densities of birds were observed in areas with heath, grass (fescue), and beach grass and pea vegetation types than in areas with other vegetation types. However, densities within these favoured vegetation types were constant with increasing transect length, which appears to be contrary to patterns expected from using published models of the effects of breeding habitat patch size on bird population density. Topographical constraints characteristic of Sable Island may impose limits on the birds' territorial boundaries and constrain density, independently of patch size. [ABSTRACT FROM AUTHOR]