Within-Season Breeding Dispersal in Prairie Warblers and Other Passerines

Abstract

We examine the hypothesis that avoidance of predation on the nest can select for within-season breeding dispersal, as it does for between-season breeding dispersal. Only five studies have adequately tested this hypothesis against a null hypothesis, e.g., that dispersal is more likely to occur following a failure than following a successful nesting attempt, and all supporta t least one of the predictionso f the predation-avoidanceh ypothesis.W e also find supportf or the hypothesisi n PrairieW arblers( Dendroicad iscolor):la te-cyclel osses resultedi n a greaterp robabilityo f dispersal.T wo alternativeh ypothesesm ay explainw ithinseason breeding dispersal: dispersal to permit more rapid renesting and dispersal to avoid depleted resources. Neither is supported in Prairie Warblers. Only one of the five earlier studies has tested either alternative. Although there is a clear need for further testing of all of these hypothesest he ratherl imited existing data do suggestt hat predation-avoidanceis important in establishing within-season patterns of breeding dispersal.