Yellow wing-patch of a nestling Horsfield's hawk cuckoo Cuculus fugax induces miscognition by hosts: mimicking a gape?


  • Keita D. Tanaka,

  • Gen Morimoto,

  • Keisuke Ueda

Keita D. Tanaka, Gen Morimoto and Keisuke Ueda, Department of Life Sciences, Rikkyo University, Ueda Laboratory (4213), 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo 171-8501, Japan. E-mail:


A chick of the Horsfield's hawk cuckoo Cuculus fugax has a vivid yellow skin patch on each wing-bend, which is very similar in colour to its own gape. Almost every time a host parent delivers food, the chick explicitly displays the wing-patch by raising and shaking the wing. We observed that host parents tried to place food onto the wing-patch of the nestling instead of into its mouth. The wing-patch would be perceived as a gape by host parents, possibly resulting in an overestimation of brood size. Signals induced by the wing-patch may vary with the luminosity of environments.