(605) Monticola rufiventris Jard. & Selby.
THE CHESTNUT-BELLIED ROCK-THRUSH.
Monticola erythrogastra, Fauna B. I., Birds, 2nd ed. vol. ii, p. 170.
Monticola rufiventris, ibid. vol. viii, p. 625.
This Rock-Thrush is found throughout the Himalayas from Murree (Whistler) to Setchuan. It also occurs in the mountains of Yunnan and Burma but may not breed in the latter. The Chinesebirds, which extend East to Fokhien, should probably be separated tinder another name.
They breed at all heights between 4,000 and 8,000 feet. ; In the Khasia Hills we found them common between 4,000 and 6,000 feet and in the Naga Hills they breed at least as high as 8,000 feet ; Thompson found them breeding in Kuman at about 6,000 ; Rattray found nests near Murree between 5,000 and 7,000, and at Mussoorie, where Mackinnon also obtained nests, between 4,000 and 6,000 feet ; Cock took a nest at Dharamsala at about 4,000 feet, whilst Hodgson seems to have got them at about the same elevation in Nepal.
I have seen many nests of this Thrush and the very great majority of these have been built in crevices or holes in rocks in the faces of cliffs or on ledges and projections forming part of the rock-face itself. Sometimes the rocks may have been huge boulders beside a path but, more often, they formed part of the precipitous cliffs abounding on the borders of the Khasia Hills district in Assam. In these the birds nearly always selected holes in which they could place their nests so as to be invisible both from below and from above, and most were detected by seeing the birds go in or out. Often, also, the sides of the cliff on the less vertical portions are well wooded and, even on the steepest parts, there is almost invari¬ably a lot of vegetation growing in the broken places where earth has lodged. This, of course, makes the nest still harder to locate, even after one has noticed the parent birds.
Sometimes the nest is placed on banks, in hollows or among the roots of some tree, or on a ledge under the crest of the bank. In such cases a well-sheltered place in forest is usually selected and the nest is more or less concealed by the surrounding herbage.
The nest itself varies very much in construction, materials and size. Those built in crevices in rocks are, more often than not, very untidy, shallow cups or pads made of moss, roots, grass, straw, leaves and other vegetable oddments. Moss generally forms a considerable proportion of the nest but the birds seem to be satisfied with almost any material soft enough for the purpose and handy for their work. I have seen nests made entirely of grass and roots, one made entirely of very coarse grass, the ends of which stuck out many inches from the crevice and so betrayed the presence of the nest. Others are made partially of fern-fronds, bracken and lichen. When, however, the birds place their nest in a hole in a bush they make quite a neat compact cup-nest of green moss with a few dead leaves, roots or a little grass added, well lined with roots, fibre or grass and, very occasionally, with hair or wool. These latter nests average somewhere about 5.1/2 to 6 inches across by about 3 to 4 inches deep externally, and have small, compact egg-cavities of about 3.1/2 inches in diameter and a full 2 inches deep. The nests in crevices average much more across and run up to 8 inches, whilst in depth they are very seldom more than 2 inches, generally with very shallow receptacles for the eggs. A nest found by Hume, “placed at the root of a tree in forest, was composed almost entirely of moss.” In Kuman Thompson describes some taken by him as made “of mosses, twigs and small roots, some six inches in diameter, on the ground under a rock or stump, or in a hole.” Marshall, who found them breeding in clefts in banks round about Naini Tal, says that they were “neatly made of moss and lined with a little grass and a few roots.”
I think they often have two broods. In Assam nearly all my eggs were taken in May and June, but I also found young out of their nests by the first week in the former month. So, too, Thompson obtained eggs in Kuman in June and July, whilst Marshall found “half-fledged young” and “just fledged young” between the 29th April and the 7th May. My earliest record for eggs is the 5th April (Kuman) and the latest 23rd July (Khasia Hills).
They lay four to six eggs, generally five or six, which are more like large eggs of Muscisylvia or of the genus Niltava than those of other Thrushes. The ground-colour varies from a pale yellowish cream, almost white, to a fairly deep buff, the whole surface densely covered with tiny freckles of reddish. As examples of the two extremes of coloration I have two clutches, one of which appears to be creamy white, just showing a faint cloud of freckles at the larger end, whilst the other appears to be a deep reddish-buff, unicoloured in two eggs but definitely freckled with dark reddish in the others. In between these two there is every shade of colour but, in nearly all, the freckles are obvious.
In shape they vary from short, broad ovals to rather long ovals, but in all they are blunt at the smaller end. The texture is fine, close and hard, the surface slightly to decidedly glossy.
Seventy-five eggs average 26.8 x 19.9 mm. : maxima 29.5 x 20.0 and 27.4 x 21.1 mm. ; minima 24.3 x 19.6 and 26.0 x 19.0 mm.
Both sexes take part in incubation but, apparently, the hen does more than the cock, as we seldom succeeded in snaring the latter on the nest. Both birds take an equal part in building the nest.
605. Monticola ruflventris
(605) Monticola rufiventris Jard. & Selby.