First Evidence of Mutually Exclusive Home Ranges in the Two Main Colonies of Lesser Kestrels in Italy

Animals compete for resources, and one way to ensure access to resources is by excluding competitors from the area containing the resources. Advances in tracking technology make it possible to quantify the overlap in home ranges between individuals and between populations. We present the first evidence of space partitioning between the two main Lesser Kestrel Falco naumanni colonies with the highest numbers of individuals in Italy, and with the highest densities of Lesser Kestrels in inhabited areas in their Eurasian breeding range. Using GPS data loggers, we collected 41,126 GPS points of Lesser Kestrels from both colonies during the nestling period. Home range overlap between the two colonies was almost zero at both 100%- and 99%-isopleths, and zero at 95%- and 90%-isopleths. Using a randomization procedure, we could show that home ranges were more spatially-segregated than expected by chance. We did detect increased overlap in home ranges among individuals within colonies. Although our results require further confirmation, they suggest that competition for food between colonies is weaker due to this strategy of spatial segregation of foraging areas. Our study confirms the recent notion that between-colony areal segregation may be the norm in colonial central-place foragers.