The other swift commonly seen in the Himalayas is the Alpine swift (_Cypselus melba_). This is distinguishable from the Indian species by its white abdomen and dark rump. It is perhaps the swiftest flier among birds. Like the species already described, it utters a shrill cry when on the wing. THE CUCULIDAE OR CUCKOO FAMILY It is not possible for anyone of sound hearing to be an hour in a hill station in the early summer without being aware of the presence of cuckoos. The Himalayas literally teem with them. From March to June, or even July, the cheerful double note of the common cuckoo (_Cuculus canorus_) emanates from every second tree. This species, as all the world knows, looks like a hawk and flies like a hawk. According to some naturalists, the cuckoo profits by its similarity to a bird of prey. The little birds which it imposes upon are supposed to fly away in terror when they see it, thus allowing it to work unmolested its wicked will in their nests. My experience is that little birds have a habit of attacking birds of prey that venture near their nest. The presence of eggs or young ones makes the most timid creatures as bold as the proverbial lion. I therefore do not believe that these cuckoos which resemble birds of prey derive any benefit therefrom. The hen European cuckoo differs very slightly from the cock. In some species, as, for example, the famous "brain-fever bird" (_Hierococcyx varius_), there is no external difference between the sexes, while in others, such as the Indian koel (_Eudynamis honorata_), and the violet cuckoo (_Chrysococcyx xanthorhynchus_), the sexes are very dissimilar. I commend these facts to the notice of those who profess to explain sexual dimorphism (the different appearance of the sexes) by means of natural or sexual selection. The comfortable theory that the hens are less showily coloured than the cocks, because they stand in greater need of protective colouring while sitting on the nest, cannot be applied to the parasitic cuckoos, for these build no nests, neither do they incubate their eggs. In the Himalayas the common cuckoo victimises chiefly pipits, larks, and chats, but its eggs have been found in the nests of many other birds, including the magpie-robin, white-cheeked bulbul, spotted forktail, rufous-backed shrike, and the jungle babbler. The eggs of _Cuculus canorus_ display considerable variation in colour. Those who are interested in the subject are referred to Mr. Stuart Baker's papers on the Oology of the Indian Cuckoos in Volume XVII of the _Journal of the Bombay Natural History Society_.