Читать книгу A Manual of Philippine Birds - Richard C. McGregor - Страница 177

 a1. Tail more or less forked (except in Anous); bill slender; terminal portion of culmen straight or but slightly curved; angle of lower mandible not prominent. Sterninæ (p. 86)

 a2. Tail even; bill stouter; terminal portion of culmen decidedly curved; angle of lower mandible distinct. Larinæ (p. 95)