Egg Recognition and Rejection Ability of Azure-Winged Magpies (Cyanopica cyanus)

Egg rejection is a key defense strategy that evolved in host species to overcome the detrimental effect of brood parasitism. The degree of egg rejection in host populations often reflects the history of the interaction between brood parasites and their hosts. In the present study, we conducted model egg and conspecific egg experiments in order to determine egg rejection ability in the Korean populations of Azure-winged Magpies (Cyanopica cyanus). In addition, we also monitored breeding nests of magpies to quantify intra- and inter-specific brood parasitism rates in this species. Overall, brood parasitism was rarely observed in this population of magpies. We found only one case of intra-specific brood parasitism and no cuckoo parasitism was observed among the 74 monitored nests. However, the results of artificial egg experiments demonstrated that Azure-winged Magpies have very high rejection ability against non-mimetic model eggs (96%) and mimetic conspecific eggs (30%). In conclusion, our study suggests that Azure-winged Magpies have finely-tuned egg recognition mechanisms, indicating that,in this species,the history of either intra- or inter-specific brood parasitism or both may be longer than is currently assumed. Further studies quntifying parasitism rates in other populations of this species would be necessary.