Timing of migration and patterns of winter settlement by Henslow\u27s Sparrows

Abstract

Fall arrival is an important period in the life history of migratory birds because processes during this period determine where birds spend the winter, which is linked to subsequent survival and condition at the time of spring migration. Henslow\u27s Sparrows (Ammodramus henslowii) winter in savannas of longleaf pine (Pinus palustris), but their secretive behavior limits our knowledge of their winter ecology, including behavioral processes that lead to their documented preference of an ephemeral habitat-recently burned savannas. We expected that upon arrival Henslow\u27s Sparrows actively seek out recently burned savannas and that their over-winter location is dependent on intraspecific interactions during the arrival period. We conducted a 2-year mark-recapture study in southeastern Louisiana longleaf pine savannas to examine these predictions. Bird densities were highest in savannas burned during the previous growing season. There was a large turnover of transient individuals in October and early November, but the proportion of dispersing birds was not related to the number of years since fire or to the bird\u27s age or sex. Early-season movements did not result in skewed age or sex distributions associated with years since fire, suggesting the lack of a class-mediated competitive hierarchy. Birds were then site faithful from late November through spring departure, which began in March and lasted through mid April, with males departing first. © The Cooper Ornithological Society 2009