First discovery on interspecific parental care of Siberian stonechat (Saxicola maurus) nestlings provided by a male White wagtail (Motacilla alba)

Interspecific parental behavior has been reported across worldwide,
especially in Europe and North America, yet relatively little information
is available from East Asia. We present the first known interspecific
parental care by a white wagtail (Motacilla alba) at a nest of Siberian
stonechat (Saxicola maurus), documented by video in the farmland of
northwest Yunnan, China. We quantify parental behavior and describe
aggressive events between the adult Siberian stonechats and the White
wagtail. Despite incurring no obvious fitness benefit, the White wagtail
did significantly more feeding attempts than either parent of the Siberian
stonechats, but did not show significant difference in sanitation
maneuvers compared to each sex of the stonechat parent. Moreover, the
three birds’ investment, in terms of food delivery and fecal-sac removal,
distributed evenly among the five nestlings at the nest. Although
proximate causes of this behavior are unclear, close nest vicinity with
host young’s loud begging and the loss of wagtail’s offspring or eggs may
have triggered this behavior.