(554) Muscisylvia leucura Hodgs.
THE WHITE-TAILED BLUE ROBIN.
Notodela leucura, Fauna B. I., Birds, 2nd ed. vol. ii, p. 106.
Muscisylvia leucura, ibid. vol. vii, p. 111.
This Robin, which was described from Nepal, extends East through Sikkim to the extreme East and South of the Assam Hill ranges and thence through those of Burma and the Malay States as far South as Perak. North-East it occurs in Yunnan, Shan States, Northern Siam and Annam. Blyth recorded it from as far West as Mussoorie, a record which has never been confirmed, but Dods¬worth obtained it in the Simla States.
The White-tailed Blue Robin breeds freely in Sikkim from about 4,000 feet up to 8,000 or 9,000 feet and Stevens observed it in the Mai Kola Valley, East Nepal, at the former elevation. In Assam it breeds from 4,000 to 7,000 feet in great numbers and between 3,000 and 4,000 and, again, between 7,000 and 9,000 feet in smaller numbers.
It is entirely a forest bird, so far as my own observations go, keeping preferably to evergreen forest of big trees with plenty of undergrowth and, almost invariably, close to some small stream. In the Khasia Hills it also frequented Pine forest but kept to the borders of the streams, along which there was always a considerable mixture of evergreen, small tree and bush-jungle. I never saw the bird or its nest in the drier portions of Pine forest, nor did any of my collectors ever take its nest in such areas.
It places its nest among boulders beside streams or in wet ravines, in grassy or mossy banks in similar places ; sometimes in among the roots of trees overhanging streams or, less often, in holes in dead trees or stumps a few feet from the ground. Its favourite site, however, is a crack or hole in the face of some vertical rock on, or close to, the banks of a stream, the hollow selected being most often a comparatively small one.
A very unusual position from which I took one nest was in among the branches, close to the trunk, of a tree which had fallen across a stream. This nest was rather large and domed and, until the bird flew out, I half expected it to be a very neat nest of a Dipper.
The nests found by me in the Assam Hills were almost invariably cup-shaped, but they were equally invariably placed in such positions that they were well protected from above and, of those found in more or less open banks, perhaps one in every ten was domed or semi-domed. In Sikkim most nests seem to be domed. Gammie writes thus of nests sent by him to Hume :—“Two nests of the White-tailed Blue Robin taken in May at 5,000 feet elevation were placed in the face of banks, among scrub near large forest. They were hooded with lateral entrances and each contained three set eggs. They were composed of fine roots intermixed with a few leaves ; a few pieces of green moss were stuck here and there on the outside to aid in concealment. Externally they measured 5.1/2 inches wide and the same deep ; the egg-cavity is 2.5 inches wide by 1 deep, with an entrance of 2.25 diameter.”
Hume adds to this : “Numerous nests of this species sent me from Sikkim show that the nest is always a compact, more or less deep cup, more or less hooded or domed where plants or rocks do not form sufficient shelter. The chief material of which the nest is always composed are extremely fine black fibrous rootlets felted closely together ; a good many dead leaves are generally incorporated towards the base of the structure, and fern-leaves (withered or green) and green moss are in many cases more or less profusely woven on to the outer surface of the sides. Where, as sometimes happens, the nest is placed in a cleft of a bank, it consists entirely of dead leaves and black rootlets, only a little moss being attached to the outer lip of the cup or the summit of the hood, as the case may be.”
To the foregoing description there is little to be added but, in the Assam Hills, the birds used far more green moss in the construction of the outer parts of their nests, so that they appeared to be made entirely of living green moss, lined with fine roots ; it was only, therefore, when the nests were pulled to pieces that their real construction could be ascertained. I have seen nests placed in small holes in the flat face of a rock on which there was no vegetation of any kind and which shone black and wet with the constant trickle of water draining over them. The vivid patch of green moss was very conspicuous but, to those not knowing what to look for, would have been passed by as a patch of moss growing in a crevice.
The cup-nests found by me averaged about 6 inches in diameter by 4 inches deep externally, or rather less, by 2 inches internally either way.
Most birds breed in May and June but I have taken eggs as early as the 4th April and as late as 10th August, the majority of birds having two broods every year, using the same nest for the two broods.
The female does most of the incubation but not all, as I have several times snared the males on the nest. The male also takes part in the building of the nest.
The eggs generally number three only in Sikkim but in Assam nearly always four.
Examined cursorily they appear to be uniform pinkish clay- coloured eggs, varying from very pale cream to a deep buff clay- colour. If examined closely with a magnifying glass they will be seen to be closely stippled all over with pale reddish clay and, in a few eggs, the stippling is visible to the naked eye, occasionally the markings becoming tiny well-marked blotches. The texture is hard, fine and very close, most eggs having a fine surface-gloss, whilst only exceptional eggs are glossless. In shape they are moderate ovals, very little compressed at the smaller end. Indi¬vidual eggs could hardly be distinguished from those of Niltava grandis but, as a series, they are more uniformly coloured, harder shelled, more glossy, as well as being a broader oval in shape.
One hundred eggs average 23.3 x 17.1 mm. : maxima 25.4 x 18.1 and 24.1 x 8.4 mm. , minima 20.1 x 17.4 and 21.4 x 15.9 mm.
554. Muscisylvia leucura
(554) Muscisylvia leucura Hodgs.