The genus Microtarsus may be recognized by its very ample and lengthened tail-coverts, rounded tail and the extraordinary development of the feathers of the lower back and rump, which are moreover barred with black; in this respect Microtarsus shows great affinities to Pinarocichla.
In this genus the feathers of the head, though erectile, are exceedingly short and glossy. The bill is about half the length of the head, and the rictal bristles are well-developed. The tarsus is very short but fairly stout. The plumage of all the known species is very pleasing.
Of the three species found within our limits it is extremely difficult to decide what relationship M. m. melanocephalus and M. cinereoventris bear to one another. It is true the former is often found in flocks with no individual of the latter but neither Mr. H. A.. Hole, who knew this bird very well, nor I myself have ever seen a flock of the latter without some of the former. The plumage of the Grey-breasted Bulbul is merely that of the Black-headed Bulbul with the yellow eliminated on some portions and this in varying degree. One of Lord Tweeddale's birds is described by him as being "in a stage of transition from yellow to grey." A specimen in the collection of Mr. Hole showed"traces of green on the hind-neck but was otherwise of purely cinereoventris type; a third, a young male shot by myself, appears also to be in a transition stage between the two forms. I expect, when the necessary evidence is obtainable, the two will be found to be one and the same bird. Age and sex have nothing to do with the matter, but no one has yet been able to prove that they breed together, however closely they may accompany one another in the non-breeding season.
Key to Species and Subspecies.
A. Lower plumage yellow or olive-yellow…………., [cephalus, p. 423.
a.Head entirely black M, melanocephalus melano-
B.Head above bluish grey.
a1. Upper tail-coverts yellow .... M. m. fusciflavescens, p. 42-5.
b1. Upper tail-coverts bluish grey . M. poiocephalus, p. 425.
B. Lower plumage bluish grey M. cinereoventris, p. 426.
* Sharpe shows that P. pusillus of Salvadori, 1874, is preoccupied by Gray, Genera Birds, i, p. 237, and cannot be used. He therefore proposes (Cat. B. M., 1881, Appendix, p. 401), P. salvadorii, but though this stands as the name for the Sumatran race, erythropthalmus of Hume has priority as the specific name.