Читать книгу A Manual of Philippine Birds - Richard C. McGregor - Страница 181

 a1. Black or dark gray below (adults in summer).b1. Upper tail-coverts and tail white; under wing-coverts black. leucoptera (p. 86)b2. Upper tail-coverts and tail gray; under wing-coverts white. hybrida (p. 87)

 a2. White below (adults in winter and young).b1. Tail white. leucoptera (p. 86)b2. Tail gray.c1. Rump gray like back. hybrida (p. 87)c2. Rump white (young). leucoptera (p. 86)