The genus Thamnobia contains two species, one or other of which is found over a considerable portion of India.
I have much hesitation in placing this genus here. It is the only genus of the Turdidae, with the exception of the Accentorinae, in which the tarsus is strongly or at all scutellated; the bill is, moreover, quite of a different character to that of any of the Thrush tribe, and the rictal bristles are reduced to a minimum. The young are mottled to a slight extent only. A better place may possibly hereafter be found for it.
In Thamnobia the bill is slender and curved downwards, the wing is very rounded, and the tarsus is strongly scutellated in front.
The two species of this genus appear to run into each other at the common point of meeting in about the latitude of Bombay; but with reference to this, two points should be carefully regarded. They are both subject to two kinds of change of plumage. One change is caused by the ordinary wearing away of the margins of the feathers during the winter, and the other, coincident in time with this, is caused by the further abrasion of the feathers after the margins are worn off. In consequence of these changes it is difficult for nine months of the year to be quite certain to which species any particular specimen may belong if the abrasion of the feathers has been at all normal. I have had no difficulty, however, in separating autumnal freshly-moulted birds, and they can be ranged into two series, each of which is found to occupy a different geographical area. In a certain zone, from Ahmednagar to the mouth of the Godavari valley, both species occur, but they are to be separated even here if birds in good plumage be examined.
The Indian Robins, as they are termed by residents in India, are familiar birds, being found in compounds, &c, and nesting in houses, or in their immediate vicinity. These birds feed a good deal on the ground, and have the habit of erecting the tail after the fashion of Robins. Both "species are resident. The sexes are different, and while the males of the two species are not difficult to discriminate, the females are very close to each other.
Key to the Species.
a. With white on the wing-coverts.
a1. Upper plumage sandy brown…………………… T. cambaiensis p. 114.
b1. Upper plumage black……………………T. fulicata p. 115.
b. With no white on the wing-coverts. ……………………T. cambaiensis p. 114. & T. fulicata p. 115.