Cat. Birds Brit. Mus. xix. 1891, pp. 122-160.
The hallux is often aborted, producing a tridactylous, instead of a zygodactylous, foot (cf. p. [10]).
Cat. Birds Brit. Mus. xviii. 1890.
Mr. Abel Chapman (Wild Spain, p. 256) says that the Spanish Green Woodpecker breeds twice a year; and its British congener at times does likewise.
A Mexican species stores acorns in hollow stems of plants, but subsequently sticks them in holes bored in branches. Baird, Brewer, and Ridgway, N. Amer. Birds, ii. 1874, pp. 569-572.