Specific floater home ranges and prospective behaviour in the European starling, Sturnus vulgaris

In many bird species, floaters are present on the breeding grounds in one or more years before they breed. There is increasing evidence that they have specific home ranges in which they search for information about current and future breeding opportunities. We investigated the role of prospecting in a migratory European starling (Sturnus vulgaris) population. Radio-tracking showed that male starling floaters use specific home range areas during the breeding period. Nest-box observations demonstrated that non-parental nest intrusion is common in the starling and that it is significantly more frequent during the nestling than during the incubation period. In addition, small groups of nest boxes were more likely to be occupied by starlings if they had been put up during the preceding breeding season. The results suggest that floaters try to acquire information about local breeding communities. One specific type of information may be the location of potential breeding sites.