(580) Turdus dissimilis Blyth.
THE BLACK-BREASTED THRUSH.
Turdus dissimilis, Fauna B. I., Birds, 2nd ed. vol. ii, p. 140.
This is the most Eastern of our Indian-breeding Thrushes. It is found in the hill-ranges of Assam, South of the Brahmapootra, and thence extends through the Chin, Kachin and Bhamo Hills and the Shan States to Yunnan. In Assam it breeds between 4,000 feet and the highest ranges, in the Khasia and Cachar Hills up to about 6,500 feet, in the Naga Hills up to 8,000 certainly, and 9,000 probably, and in Yunnan up to 10,000 feet.
It is a bird of densely forested country, breeding in the interior of damp evergreen woods with ample undergrowth. In the Khasia Hills its favourite haunts were mixed Oak and Rhododendron forest, every tree overgrown with luxuriant moss, orchids and tree- ferns, the ground below being broken up by huge boulders and rocky ravines. In North Cachar I found its nest in rather more open forest of stunted Oak but, here too, the undergrowth was fairly dense ; bracken, ferns, moss and orchids growing in the same great masses as in the Khasia Hills. In the Chin Hills both Hopwood and Mackenzie obtained it breeding in much the same kind of country, the nest always being built in dense forest and not open country, whilst Harington and Macdonald found it in similar country in the Shan States.
The nesting-site in Assam was always on a tree, most often between 10 and 20 feet from the ground, or a bash between 4 and 10 feet. The favourite site was undoubtedly a Rhododen¬dron-tree, where, wedged into a fork of a gnarled and twisted branch, it was quite concealed by its mossy surroundings until the bird leaving it disclosed its presence. If a small Oak was selected, the actual position was in among dense clusters of leaves, which afforded effectual concealment. Similarly, if built in high bushes, it was always in those with dense foliage.
In the Chin Hills Mackenzie and Hopwood found that the birds made use of banks as nesting-sites as often as, or more often than, trees. Even in these cases they were carefully hidden by overhanging weeds or grass.
The nests are quite typical Thrushes’ nests, but only in rare cases is there any intermediate mud lining between the body of the nest and the true hning. The main structure of the nest is a well-put-together cup almost entirely made of roots and grass, with a few dead leaves or fern-fronds incorporated with them. Inside this is the true lining, consisting of roots—the coarser under¬neath, the finer above—next the eggs. Outside the whole nest is nearly all moss, worked green and fresh into the inner structure of roots and grass. The dimensions of the whole nest are about 6 inches in diameter by nearly 4 inches in depth but, if all the straggling ends of moss are taken into consideration, the diameter would run up to 8 or even 9 inches. The inner cup, which is very neatly finished off, measures, on an average, about 3.1/2 inches in diameter by about 2.1/2 in depth.
A rather unusual nest taken by Mackenzie is described by him as follows :—“Nest on the ground ; the base made of mud, on which was piled up moss with a shallow cup of roots on the top. The bird was shot off the nest.” Another nest, also taken on the ground, was similar. On the other hand, the nests taken by Harington at Gangiri, Shan States, “are placed at the end of branches 12 feet from the ground and composed of moss and grass with plenty of mud. In fact the nests were very heavy for their size ; lined with fine grass.”
The breeding season in Assam is May and June, running into the early part of July. In the Chin Hills it seems to be from the middle of April to the second week in June, while further East again most eggs are laid in April and early May.
In Northern Burma this Thrush lays two to four eggs, as frequently Mackenzie took clutches of two which showed signs of incubation. In Assam, however, four was the normal clutch, three being unusual. The two nests found by Harington at 5,500 feet in the Shan States on the 15th May each contained three eggs.
The range of variation is extraordinary. A few eggs are of the ordinary greenish Blackbird type, more are of the erythristic type, and one pair, taken by Mackenzie, looks an almost uniform brick- red, so closely do the tiny longitudinal freckles cover the whole surface. From this closely marked form they range up to eggs with a pale green, yellow-green or buff ground, with a few large blotches of deep red or purple-brown. Other eggs are of the Missel-Thrush type, and others again are like eggs of the Geokichla group, pale, rather faintly marked with reddish-brown and pale lilac. One pair of Chin Hills eggs has a darkish dull green ground densely marked with blurred blotches of red-brown. Many eggs of this Thrush are only distinguishable by their texture from those of Geokichla citrina, these latter having a harder, finer shell, with much greater gloss.
In shape the eggs are rather broad ovals but usually decidedly compressed at the smaller end, whilst rather longer, more pointed ovals are not rare.
Fifty eggs average 26.8 x 19.8 mm. : maxima 29.2 x 20.0 and 27.2 x 21.0 mm. ; minima 21.0 x 20.0 and 26.0 x 18.3 mm.
Both sexes take part in incubation, as I have trapped both on the nest and eggs in day-time. Both also help in building the nest, though I cannot say whether the cock bird does more than bring the materials for his wife to incorporate in the nest.
They are not shy birds, and can generally be approached on the nest near enough for identification and, once or twice, I have had the female, much the bolder of the pair, sit tight on her eggs and blink at me from a distance of only two or three yards.
580. Tardus dissimilis
(580) Turdus dissimilis Blyth.