Attributes / relations provided by
♦ 1del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.).
Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona.
♦ 2Vormela peregusna, Wanda A. Gorsuch and Serge Larivière, MAMMALIAN SPECIES No. 779, pp. 1-5 (2005)