Egg rejection by Iberian azure‐winged magpies Cyanopica cyanus in the absence of brood parasitism

The Iberian azure‐winged magpie Cyanopica cyanus shows a remarkable ability to discriminate against great spotted cuckoo Clamator glandarius eggs. Here, I studied whether egg recognition in this species could be a derived feature resulting from intra‐specific brood parasitism. Azure‐winged magpies showed a very high level of discrimination and rejection of great spotted cuckoo models (73.7%), and of conspecific eggs (42.8%), even when no evidence of great spotted cuckoo or conspecific brood parasitism has been found in the population. Azure‐winged magpie discriminated more readily than magpies, the current favourite host of the great spotted cuckoo. The high rejection rate of conspecific eggs by the azure‐winged magpie suggests that it is quite possible that egg discrimination in this species evolved in response to conspecific brood parasitism rather than to cuckoo parasitism.