Most birds have hollow bones which are filled with air. It was claimed by those who like to find a use for everything that this was an obvious adaptation for purposes of flight, but when one reflects that, in some of the Ostrich and Emu group, the members of which never fly, the bones are strongly "pneumatic," while in Terns and Swifts, and some other flying birds, the bones are solid, one must hesitate before generalizing even about such an apparently obvious matter. Swifts are in no way related to Swallows, but are close to Humming Birds, which are born with a wide, Swift-like mouth.
ORDER XVIII.—CORACIIFORMES, PICARIAN BIRDS.
F. 78. Steatornithidae, Oil-Bird, Guacharo, 1 sp. Nl.
F. 79. PODARGIDAE (6), FROGMOUTHS, 32 sp.—20(20)A., 12(12)O.
4
7
217 Tawny Frogmouth (Tawny-shouldered), Mopoke (e), Podargus strigoides, A.T.
Stat. c. open forest 18
Upper brown freckled grayish-white and darker-brown; wings lighter, spotted black and buff; tawny patch on wing; tail tawny-brown barred blackish-brown; wide bill brown; nocturnal; f., sim. Insects. "Oom, oom."