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Dryad

Data for: Patterns of extra-territorial nestbox visits in a songbird suggest a role in extra-pair mating

Data files

Nov 16, 2022 version files 19.45 MB

Abstract

Many animals make visits outside of their territory during the breeding period, but these are typically infrequent and difficult to observe. As a consequence, comprehensive data on extra-territorial movements at the population-level are scarce and the function of this behavior remains poorly understood. Using an automated nestbox visit tracking system in a wild blue tit population over six breeding seasons, we recorded all extra-territorial nestbox visits (n=22137) related to 1195 individual breeding attempts (761 unique individuals). Sixty-two percent of breeders made at least one extra-territorial visit between the onset of nest building and the day of fledging of their offspring, and individuals visited another nestbox on average on 11% of the days during this period. Visit behavior differed clearly between the sexes, with males making over three times as many extra-territorial forays as females. There was a strong overall seasonal decline in visit behavior, but this was sex dependent, with females showing a strong reduction in the number of extra-territorial visits before the onset of egg laying and males showing a strong and sudden reduction on the day their offspring hatched. The likelihood of visiting a particular nestbox declined sharply with the distance to that box, and blue tits almost exclusively visited direct neighbors. Individuals were more likely to have extra-pair offspring with an individual whose box they visited, but they were not more likely to disperse to a box they had visited. Thus, our results are inconsistent with the hypothesis that extra-territorial nestbox visits serve to inform dispersal decisions, but suggest that such visits are linked to extra-pair mating opportunities.