So great is the number of species of warbler which either visit India every winter or remain always in the country, so small and insignificant in appearance are these birds, so greatly do they resemble one another, and so similar are their habits, that even the expert ornithologist cannot identify the majority of them unless, having the skin in one hand and a key to the warblers in the other, he sets himself thinking strenuously. For these reasons I pay but little attention to the warbler clan. Usually when I meet one of them, I am content to set him down as a warbler and let him depart in peace. But I make a few exceptions in the case of those that I may perhaps call warblers of distinction--warblers that stand out from among their fellows on account of their architectural skill, their peculiar habits, or unusual colouring. The famous tailor-bird (Orthotomus sartorius) is the best known of the warblers distinguished on account of architectural skill. As a warbler of peculiar habits, I may cite the ashy wren-warbler (Prinia socialis), which, as it flits about among the bushes, makes a curious snapping noise, the cause of which has not yet been satisfactorily determined. As warblers of unusual colouring, the flycatcher-warblers are pre-eminent. In appearance these resemble tits or white-eyes rather than the typical quaker-like warblers.
Cryptolopha xanthoschista and Hodgson's grey-headed flycatcher-warbler are the names that ornithologists have given to a very small bird. But, diminutive though he be, he is heard, if not seen, more often than any other bird in all parts of the Western Himalayas. It is impossible for a human being to visit any station between Naini Tal and Murree without remarking this warbler. It is no exaggeration to state that the bird's voice is heard in every second tree. Oates writes of the flycatcher-warblers, "they are not known to have any song." This is true or the reverse, according to the interpretation placed on the word "song." If song denotes only sweet melodies such as those of the shama and the nightingale, then indeed flycatcher-warblers are not singers. Nevertheless they incessantly make a joyful noise. I can vouch for the fact that their lay is heard all day long from March to October. Before attempting to describe the familiar sound, I deem it prudent to recall to the mind of the reader the notice that once appeared in a third-rate music-hall:--"The audience are respectfully requested not to throw things at the pianist. He is doing his best." To say that this warbler emits incessantly four or five high-pitched, not very musical notes, is to give but a poor rendering of his vocal efforts, but it is, I fear, the best I can do for him. He is small, so that the volume of sound he emits is not great, but it is penetrating. Even as the cheery lay of the Otocompsa bulbuls forms the dominant note of the bird chorus in our southern hill stations, so does the less melodious but not less cheerful call of the flycatcher-warblers run as an undercurrent through the melody of the feathered choir of the Himalayas.
In what follows I shall speak of Hodgson's grey-headed flycatcher-warbler as our hero, because I shrink from constant repetition of his double double-barrelled name. I should prefer to give him Jerdon's name, the white-browed warbler, but for the fact that there are a score or more other warblers with white eyebrows. Our hero is considerably smaller than a sparrow, being only a fraction over four inches in length, and of this over one-third is composed of tail. The head and neck are grey, the former being set off by a cream-coloured eyebrow. Along the middle of the head runs a band of pale grey; this "mesial coronal band," as Oates calls it, is far more distinct in some specimens than in others. The remainder of the upper plumage is olive green, and the lower parts are bright yellow. Coloured plate, No. XX, in Hume and Henderson's Lahore to Yarkand, contains a very good reproduction of the bird. The upper picture on the plate represents our hero, the lower one depicting an allied species, Brook's grey-headed flycatcher-warbler (C. Jerdoni). It is necessary to state this because the book in question was written in 1873, since when, needless to say, the scientific names of most birds have undergone changes. The plate in question also demonstrates the slenderness of the foundation upon which specific differences among warblers rest.
Our hero is an exceedingly active little bird. He is ever on the move, and so rapid are his movements that to watch him for any length of time through field-glasses is no mean feat. He and his mate, with perhaps a few friends, hop about from leaf to leaf looking for quarry, large and small. The manner in which he stows away a caterpillar an inch long is a sight for the gods!
Sometimes two or three of these warblers attach themselves, temporarily at any rate, to one of those flocks, composed mainly of various species of tits and nuthatches, which form so well-marked a feature of all wooded hills in India. Hodgson's warblers are pugnacious little creatures. Squabbles are frequent. It is impossible to watch two or three of them for long without seeing what looks like one tiny animated golden fluff ball pursuing another from branch to branch and even from tree to tree.
The breeding season lasts from March to June. The nest is globular in shape, made of moss or coarse grass, and lined with some soft material, such as wool. The entrance is usually at one side. The nest is placed on a sloping bank at the foot of a bush, so that it is likely to escape observation unless one sees the bird flying to it. Three or four glossy white eggs are laid. Many years ago Colonel Marshall recorded the case of a nest at Naini Tal "at the side of a narrow glen with a northern aspect and about four feet above the pathway, close to a spring from which my bhisti daily draws water, the bird sitting fearlessly while passed and repassed by people going down the glen within a foot or two of the nest." At the same station I recently had a very different experience. Some weeks ago I noticed one of these warblers fly with a straw in its beak to a place on a steep bank under a small bush. I could not see what it was doing there, but in a few seconds it emerged with the bill empty. Shortly afterwards it returned with another straw. Having seen several pieces of building material carried to the spot, I descended the bank to try to find the nest. I could find nothing; the nest was evidently only just commenced. I then went back to the spot from which I had been watching the birds, but they did not return again. I had frightened them away. Individual birds of the same species sometimes differ considerably in their behaviour at the nesting season. Some will desert the nest on the slightest provocation, while others will cling to it in the most quixotic manner. It is never safe to dogmatise regarding the behaviour of birds. No sooner does an ornithologist lay down a law than some bird proceeds to break it.