Geographical Variation in Egg Rejection by Azure‐Winged Magpies ( <i>Cyanopica cyanus</i> ) Across China

Brood parasitism negatively affects the reproductive success of hosts, leading many hosts to evolve defense strategies to recognize and reject parasitized eggs. While studies have shown that hosts may adjust their defensive behavior according to parasitism risk, whether different geographical populations of the azure-winged magpie (<i>Cyanopica cyanus</i>), which are parasitized by multiple cuckoo species and face varying parasitism risks, exhibit geographical variation in egg rejection behavior is unclear. As studies have shown that the color of model eggs can influence the egg rejection behavior of hosts, we also tested whether red or blue model eggs would affect the egg rejection behavior of the azure-winged magpies. From April to June in 2023, we investigated the egg recognition ability of azure-winged magpie populations in Fusong County, Jilin Province; Huangpi District, Hubei Province; and Luqu County, Gansu Province, China. The results showed that the azure-winged magpie populations in all three regions rejected approximately 100% of the model eggs, with no significant difference in rejection rates between red and blue model eggs. This study revealed that Chinese populations of azure-winged magpies exhibited high egg recognition ability. There was no geographical variation in their egg rejection behavior when presented with non-mimetic blue or red model eggs. This study provided basic data for further research on the anti-parasitic strategies of the azure-winged magpie.