First detailed report of cooperative breeding in red-billed blue magpie (Urocissa erythrorhyncha) in central China

The cooperative breeding system of birds is an ideal model for studying and exploring social evolution in animals. However, a basic question, i.e., how many cooperative-breeding bird species exist in the world, remains controversial due to the lack of accumulated knowledge of the natural history of many birds, which prevents a generalized understanding of the evolution of cooperative breeding in birds and challenges the accuracy of results in many comparative studies. In this paper, we provide the first evidence of cooperative breeding in red-billed blue magpies (Urocissa erythrorhyncha). Moreover, we document and discuss potential relationships between cooperative breeding and nest predation, brood parasitism and breeding performance in U. erythrorhyncha. These findings about cooperative breeding in red-billed blue magpie will lay a foundation for further research on this species' sociality and provide useful insights into the evolution of cooperative breeding and other social systems in birds.