The northern hawk-cuckoo,rufous hawk-cuckoo, or Horsfield's hawk-cuckoo (Hierococcyx hyperythrus) is a bird in the family Cuculidae formerly thought to be conspecific with Hodgson's hawk-cuckoo (Hierococcyx fugax) and placed in the genus Cuculus.
Juvenile northern hawk-cuckoos have a yellow skin patch on the underside of each wing, which parents use to detect whether offspring are begging for food.[3]
^There is no evidence of this species on Sakhalin island according to Russian sources: (Гизенко А. И. Птицы Сахалинской области, М. Изд-во АН СССР, 1955. 324 с.; Судиловская А. М. 1951. Отряд Кукушки. // Птицы Советского Союза. Том 1, Под общ. ред. Г. П. Дементьева, Н. А. Гладкова. М.: Советская Наука. С. 46; Флинт В. Е., Бёме Р. Л., Костин Ю. В., Кузнецов А. А. Птицы СССР. М.: Мысль. 1968. С. 348-350.)