The addition of the adjective "Bengal" is important, for every province of India has its own special species of bulbul.
The Molpastes bulbul is a bird about half as big again as the sparrow, but with a longer tail. The black head is marked by a short crest. The cheeks are brown. There is a conspicuous crimson patch under the tail. The remainder of the plumage is brown, but each feather on the body is margined with creamy white, so that the bird is marked by a pattern that is, as "Eha" pointed out, not unlike the scales on a fish. Both ends of the tail feathers are creamy white.
Otocompsa is a far more showy bird. The crest is long and pointed and curves forward a little over the bill. There is the usual crimson patch under the tail and another on each cheek. The rest of the cheek is white, as is the lower plumage. A black necklace, interrupted in front, marks the junction of the throat and the breast. Neither of these bulbuls ascends the hills very high, but I have seen the former at the Brewery below Naini Tal.
The common bulbul of the Himalayas is the white-cheeked species (Molpastes leucogenys). This bird, which is very common at Almora, has the habits of its brethren in the plains. Its crest is pointed and its cheeks are white like those of an Otocompsa bulbul. But it has rather a weedy appearance and lacks the red feathers on the sides of the head. The patch of feathers under the tail is bright sulphur-yellow instead of crimson.
The only other species of bulbul commonly seen in the hills is a very different bird. It is known as the black bulbul (Hypsipetes psaroides).
The bulbuls that we have been considering are inoffensive little birds which lead quiet and respectable lives. Not so the black bulbuls. These are aggressive, disreputable-looking creatures which go about in disorderly, rowdy gangs.
The song of most bulbuls is a medley of pleasant tinkling notes; the cries of the black bulbuls are harsh and unlovely.
Black bulbuls look black only when seen from a distance. When closely inspected their plumage is seen to be dark grey. The bill and legs are red. The crest, I regret to say, usually looks the worse for wear. Black bulbuls seem never to descend to the ground. They keep almost exclusively to tops of lofty trees. They are very partial to the nectar enclosed within the calyces of rhododendron flowers. A party of half a dozen untidy black birds, with moderately long tails, which keep to the tops of trees and make much noise, may with certainty be set down as black bulbuls.
These curious birds form the subject of a separate essay.