Although poetic licence has ascribed the song to the female, it is the male nightingale only that sings, and for the purpose aforementioned. The note of the nightjar, on the other hand, is equally uttered by both sexes, and both also have the curious habit of repeatedly clapping the wings for several minutes together. They moreover share the business of incubation, taking day and night duty on the eggs, which, two in number, are laid on the bare ground without any pretence of a nest, and generally on open commons in the neighbourhood of patches of fern-brake. Like the owls, these birds sleep during the day and are active only when the sun goes down. It is this habit of seeking their insect food only in the gloaming which makes nightjars among the most difficult of birds to study from life, and all accounts of their feeding habits must therefore be received with caution, particularly that which compares the bristles on the mouth with baleen in whales, serving as a sort of strainer for the capture of minute flying prey. This is an interesting suggestion, and may even be sober fact; but its adoption would necessitate the bird flying open-mouthed among the oaks and other trees beneath which it finds the yellow underwings and cockchafers on which it feeds, and I have more than once watched it hunting its victims with the beak closed. I noticed this particularly when camping in the backwoods of Eastern Canada where the bird goes by the name of nighthawk. In all probability its food consists exclusively of insects, though exceptional cases have been noted in which the young birds had evidently been fed on seeds. The popular error which charges it with stealing the milk of ewes and goats, from which it derives the undeserved name of "goat-sucker," with its equivalent in several Continental languages, is another result of the imperfect light in which it is commonly observed. Needless to say, there is no truth whatever in the accusation, for the nightjar would find no more pleasure in drinking milk than we should in eating moths. Here, then, are two night-voices of very different calibre. These are not our only birds that break the silence on moonlight nights in June. The common thrush often sings far into the night, and the sedge-warbler is a persistent caroller that has often been mistaken for the nightingale. The difference in this respect between the two subjects of these remarks is that the nightjar is invariably silent all through the day, whereas the nightingale sings joyously at all hours. It is only because his splendid music is more marked in the comparative silence of the night, with little or no competition, that his daylight concert is often overlooked. JULY SWIFTS, SWALLOWS AND MARTINS SWIFTS, SWALLOWS AND MARTINS