Large-scale Input Matching by Urban Feral Pigeons (Columba livia)

Ideal Free Distribution (IFD) theory predicts the number of animals choosing habitats of differing quality. Most experimental tests of the IFD have been conducted at small spatial scales (i.e. smaller than maximum daily movement of animals) by comparing the number of animals foraging at adjacent food patches of different quality. Urban pigeons ( Columba livia ) feed in large, open aggregations, and can distribute according to predictions of the IFD at alternative food patches. In this study, we test IFD predictions over a much larger spatial scale by comparing the abundance of urban feral pigeons at four sites spread over the city centre of Montréal, Québec, Canada, to the amount of anthropogenically provided food in each site. We found that the pigeons' distribution among the four sites qualitatively matched that of resources available at these sites. After controlling for the effect of stochastic variation in food resources, two pair-wise comparisons between sites indicated undermatching, one indicated matching and three indicated overmatching of consumers to resources. These results suggest that the pigeons inhabiting the downtown area of Montréal may behave as a single population that distributes qualitatively among foraging sites in proportion to the quantity of food offered, and that deviations from expectations cannot be attributed simply to stochastic variation in the food levels at the sites.