442 CERTHIID^. black tipped with asliy, which gradually changes to white and increases in extent towards the outer tail-feathers; chin and throat pure white; remainder of lower plumage ashy slate, the under tail-coverts fringed with white; axillaries crimson.
Colours of soft parts. Iris dark brown; bill, legs and feet black-
Measurements. Total length about 170 to 180 mm.; wing 94 to 102 mm.; tail about 50 to 54 mm.; tarsus 25 to 27 mm.; culmen 27 to 32 mm. In summer the crown of the head becomes grey and the chin and throat black. The female has generally rather less black on the throat than the male. The young resemble the adult in winter plumage but there is less crimson on the wing and all the quills have each two rufous spots on the inner web. These spots gradually disappear, except on the first four large primaries, where they eventually turn white.
Distribution. The mountains of Europe and Asia, breeding throughout the Himalayas at suitable elevations and descending lower in winter, occasionally venturing actually into the plains in exceptionally cold weather.
Nidification. The Wall-Creeper breeds throughout the Hima- layas between 14,000 and 16,000 feet, in some cases as low as 12,000 feet. Whitehead found it breeding in Chitral and the Kurram Valley and Whymper actually found its nest with young in June in the Lidar Valley in Garhwal. The young were old enough to leave the nest on the 27th of that mouth. In Tibet it breeds in some numbers just above the Gyantse Plains at little over 12,000 feet, laying in the early part of May onwards. Owing to the inacces- sible places in which it builds and to its habit of placing its nest deep down in crevices of unbreakable rock, few nests have been taken in India, though the Tibetans know well many places in which it breeds. The nest is just a pad of moss and grass, more or less mixed and lined with wool, fur or hair, wedged into the bottom of some deep but narrow crevice of the rock-face of a precipitous cliff. The eggs number four to six and are pure, but rather dull, white with a few specks and spots of black or deep red-brown at the larger end. In shape they are broad ovals, decidedly compressed and pointed at the smaller end. The n)easurements of 20 eggs, including 15 mentioned by Hartert, are: — average 21-3 x 14-9 mm.; maxima 22-7 X 157 and 20-8 x 160 mm., Diinima 20*0xl4'0 mm.
Habits. This beautiful little bird haunts the face of precipitous cliffs aud great rocks, scuttling about over their surface just as the Tree-Creepers do over the trunks of great trees. Unlike the Tree-Creepers, however, they have a habit of constantly fluttering about the holes and crevices as they search for their insect food and, when so employed, they are singularly like large and beautiful butterflies. This curious habit has earned them the name of
