For further details cf. Gould, Monograph of the Odontophorinae, London, 1850.
Life Histories of N. Amer. Birds, Special Bull. i. U.S. Nat. Mus. 1892, pp. 52-56.
For hybrids of grouse, cf. Meyer, Unser Auer Rackel und Birkwild. Vienna, 1887; and Millais, Game Birds and Shooting Sketches. London, 1892.
Cf. Lloyd, Game Birds of Sweden and Norway, London, 1867; and Millais, op. cit.
T. E. Buckley, P.Z.S. 1882, pp. 112-116.