The nostrils are pervious, the tongue is sagittate, the furcula {261}is Y-shaped, and often ancylosed with the sternum, the syrinx is tracheo-bronchial. An after-shaft is present, and the down, which is uniform in the young only, is in them mottled with black and lighter tints. A most remarkable phenomenon, moreover, is the gular pouch, opening under the tongue, found in the male of some examples of _Otis tarda_ during the breeding season. This pouch becomes very small or vanishes altogether at other times of the year, and seems to be restricted to adult birds. Similar, but smaller, processes have been observed in _Eupodotis kori_, _E. edwardsi_ and, it is said, _Otis tetrax_; while dilatations of the oesophagus have been recorded in _E. australis_ and _Neotis denhami_. [Illustration: FIG. 54.–Great Bustard. _Otis tarda._ × ⅑ or ⅒.] _Otis tarda_, the Great Bustard, which, as a native, only became extinct in Norfolk about 1838, used to extend from East Lothian to Dorset, but is now merely an occasional visitor to Britain. The upper parts are mottled with rufous, buff, and {262}blackish-brown, the head is blue-grey, with long white bristles at the base of the mandible, the lower surface is white, relieved in the male by a tawny gorget for a short time during the breeding season. The primaries are black, most of the secondaries and wing-coverts white. Some other Bustards seem to have a similar vernal change of plumage. The female is smaller and has no bristles. _O. tetrax_, the Little Bustard, a straggler to our shores, is somewhat like the last species in colour, but has the cheeks and throat grey, bordered by a white line, and below this comes a broad black collar divided in front by a median white band in the nesting time. The female is brown and black, with white breast and no collar. The remaining members of the Family vary considerably in pattern of colour, being spotted, streaked, or vermiculated above, and being occasionally very dark; the head and the lower parts, moreover, are not uncommonly quite black, or the latter may be greyish-blue, as in _Trachelotis coerulescens_. The bill and feet are usually yellow, more seldom greyish or dusky. Females and young exhibit a more uniform mixture of brown, black, and buff, while rufous bases to the feathers are characteristic of the group.