Home range overlap and its genetic correlates in an avian brood parasite, the lesser cuckoo Cuculus poliocephalus

Abstract

The absence of parental care is of importance in the evolution of mating and breeding systems. However, its importance in the evolution of these systems in higher vertebrates, such as birds and mammals, has not been well defined since nearly all of them exhibit some form of parental care. Avian brood parasites thus provide a unique opportunity to explore the effect of a lack of parental care in higher vertebrates because they shift care for their progeny onto other species. We investigated the social system of an avian brood parasite, the lesser cuckoo (Cuculus poliocephalus), by using a comprehensive approach that included field observation, radio-tracking, and genetic analyses. We found that genetically unrelated, multiple males and females coexist in a single area; radio-tracking confirmed that this co-occurrence was neither temporary nor arbitrary. Instead, sympatric cuckoos appeared to share their home ranges and often chased each other for mating without antagonistic physical interaction. We conclude that the lesser cuckoo may employ a scramble competition mating system without territoriality, and that this mating system, which is unusual in higher vertebrates, may have arisen due to the absence of parental care. Future studies assessing the parentage of nestlings are needed to establish the genetic basis of this social system.