Egg rejection and egg recognition mechanism in a Chinese Azure-winged Magpie (Cyanopica cyanus) population

Recognition and rejection of foreign eggs are effective defense of hosts against brood parasitism. However, brood parasitism can impose various selection pressures on different geographic populations of the same host species. In a multiple cuckoo system in China, Azure-winged Magpies (Cyanopica cyanus) are parasitized by both Indian Cuckoos (Cuculus micropterus) and Asian Koels (Eudynamys scolopaceus). In this study, egg recognition ability and recognition mechanism of the Azure-winged Magpie were investigated using a population in Fusong, southeastern Jilin, China. The results showed that 55.6% (20/36) of the Azure-winged Magpies correctly rejected quail (Coturnix japonica) eggs in their nests, while 13.9% (5/36) of the individuals experienced rejection costs by wrongly rejecting their own eggs. Azure-winged Magpies could accurately reject the experimental eggs when the number of such eggs in the nests was the same as that of the magpie eggs. However, Azure-winged Magpies do not recognize and reject conspecific eggs (0/28). The present study indicates that the Azure-winged Magpie has moderate egg recognition ability toward non-mimetic quail eggs and shows a true recognition mechanism with rejecting foreign eggs by accurately recognizing their own eggs. However, they cannot recognize conspecific eggs.