Intraspecific Differentiation of the Oriental Cuckoo (Cuculus optatus) within the Range: Relationship with the Abundance of Host Species

Abstract

The distribution of C. optatus host-specific races within the breeding range has been analyzed. It has been found that these races are geographically separated: their distribution areas coincide with regions where the population density of corresponding race-forming host species (leaf warblers) is increased. The abundance of the brood parasite depends on the population density of race-forming host species and of accessory hosts (species laying pure white eggs). The group of accessory hosts plays an important role in areas where the proportion of race-forming species in the total population of leaf warblers is relatively small.