The explanation of the fact that one species of bird of prey leaves the plains in the hot weather, while a nearly related species remains, may perhaps be found in the nature of their food. Birds of prey are to a greater or lesser extent specialists; while quite ready to devour any small bird, reptile, or mammal which comes their way, they lay themselves out more especially to catch one particular species, and if that species migrates it follows that the bird that preys upon it will also migrate. Thus the peregrine falcon lays itself out to catch ducks and naturally goes with them to their breeding grounds, just as the hawker of cheap wares, who preys upon the _mem-sahib_, follows her to the hills in the summer.
In conclusion mention must be made of the _Corvi_ which visit us in winter. The arch-corvus, the grey-necked rascal (_Corvus splendens_), of course, abides with us all the year round. The raven, too, is to be seen at all times of the year, but is more abundant in the cold weather than in the hot. During the summer months we see comparatively few ravens; in the winter they are exceedingly numerous. Every evening towards sunset a long stream of them may be observed flying in a westerly direction to the common roosting place. There is a similar stream of crows that flies in a north-westerly direction. The rook (_Corvus frugilegus_) is a permanent resident of Kashmir and the North-Western Himalayas, but in mid-winter many individuals are driven by the cold into the Frontier Province and the Punjab; some come as far south as Lahore, where they consort with the crows. If the winter is a severe one large numbers of rooks come to Lahore, otherwise these birds are not very numerous. The same applies to the jackdaw (_Corvus monedula_), but he never comes in such numbers as the rook. There is in the octagonal bird house in the Lahore “Zoo” a compartment in which there is a “Happy Family” of ravens, rooks, and jackdaws, with an Australian crow-shrike and a Nicobar pigeon to keep them company. Thus every one who cannot already do so may learn to identify the various _Corvi_ which visit Lahore in the winter.
Nearly every village in India has its pond which becomes filled with water during the monsoon and grows drier and drier during the winter and hot weather. The pond is usually a natural depression, sometimes enlarged and deepened by human agency. Occasionally a village is situated on the edge of a lake, or _jhil_, but such fortunate villages are few and far between; the average hamlet has to be content with a small tank. This morning I came upon such a tank, in which the water had become low, leaving a wide margin of mud between it and the artificially made bank. At one end a couple of people were squatting. _Mirabile dictu_, there was not a paddy bird to be seen, and the only feathered creature disporting itself along the edge was a grey wagtail. In mid pond four domestic ducks were feeding. A tern—the Indian river tern (_Sterna seena_)—was busy at the tank, flying gracefully over the water and dipping into it every few seconds. Judging from the frequency with which the bird dived, the water must have teemed with food, but there were no signs of fish rising, so that how the eye of the tern was able to penetrate the very muddy water is a mystery. However, the tern did manage to distinguish its quarry, for, although its movements were so rapid that I was not able to discover what it was catching, I could see distinctly that, when rising, it carried something tiny in its bill.