PUBLIC INFORMATION AND TERRITORY ESTABLISHMENT IN A LOOSELY COLONIAL RAPTOR

Abstract

Evidence is increasing that animals may select habitats using direct cues (direct assessment hypothesis) and indirect cues, such as cuing on the presence of conspecifics (conspecific attraction hypothesis) and on their productivity in the previous year (public information hypothesis). We tested such hypotheses by studying the establishment of new territories (by inexperienced individuals) in the Black Kite (Milvus migrans), a long-lived, loosely colonial raptor, previously shown to exploit public information for foraging and dispersal decisions. All three hypotheses (direct assessment, conspecific attraction, and public information) were simultaneously supported; new territories were established on the basis of a complex system of integrated, direct and indirect cues, collected in the current and previous year. Exploitation of public information was allowed by the patchiness and moderate temporal predictability of breeding success (the information cue). Establishment of new territories near conspecifics involved a breeding cost for nearby previous residents, suggesting that conspecific cuing may be a form of information parasitism, at least in our system. Conspecific cuing affected nest spacing and population trend; mean nest spacing declined with colony size, while higher colony and population-level productivity in one year were followed by higher recruitment of new breeders in the following year, despite the delayed maturity of the species. All results were consistent with recent predictions by theoretical models.