First Discovery on Interspecific Parental Care of Siberian Stonechat (<scp><i>Saxicola maurus</i></scp>) Nestlings Provided by a Male White Wagtail (<scp><i>Motacilla alba</i></scp>)

Interspecific parental behavior has been reported worldwide, particularly in Europe and North America, yet relatively little information is available from East Asia. We present the first known instance of interspecific parental care by a white wagtail (<i>Motacilla alba</i>) at a Siberian stonechat (<i>Saxicola maurus</i>) nest, documented via video footage in the farmland of Northwest Yunnan, China. We quantify parental behaviors and describe aggressive interactions between the adult Siberian stonechats and the white wagtail. The white wagtail lightened the provisioning load of the male and female stonechats and increased total provisioning to nestlings to some extent. Moreover, the investment of the three birds, in terms of food delivery and fecal-sac removal, was evenly distributed among the five nestlings at the nest. Although proximate causes of this behavior are unclear, close nest vicinity with the host young's loud begging and the loss of the wagtail's offspring or eggs may have triggered this behavior.