some time since flown, he has recommenced singing vociferously at intervals throughout the day; and doubtless, in conformity with what I have observed elsewhere, will go on singing till July. How marked is the direct relation between singing and the conditions which cause high spirits, is perhaps best shown by a fact I noted on the 4th December, 1888, when, the day being not only mild but bright, the copses on Holmwood Common, Dorking, were vocal just as on a spring day, with a chorus of birds of various kinds—robins, thrushes, chaffinches, linnets, and sundry others of which I did not know the names. Ornithological works furnish verifying statements. Wood states that the hedge-sparrow continues "to sing throughout a large portion of the year, and only ceasing during the time of the ordinary molt." The song of the Blackcap, he says, "is hardly suspended throughout the year;" and of caged birds which sing continuously, save when molting, he names the Grosbeak, the Linnet, the Goldfinch, and the Siskin.
I think these facts show that the popular idea adopted by Mr. Darwin is untenable. What then is the true interpretation? Simply that like the whistling and humming of tunes by boys and men, the singing of birds results from overflow of energy—an overflow which in both cases ceases under depressing conditions. The relation between courtship and singing, so far as it can be shown to hold, is not a relation of cause and effect, but a relation of concomitance: the two are simultaneous results of the same cause. Throughout the animal kingdom at large, the commencement of reproduction is associated with an excess of those absorbed materials needful for self-maintenance; and with a consequent ability to devote a part to the maintenance of the species. This constitutional state is one with which there goes a tendency to superfluous expenditure in various forms of action—unusual vivacity of every kind, including vocal vivacity. While we thus see why pairing and singing come to be associated, we also see why there is singing at other times when the feeding and weather are favorable; and why, in some cases, as in those of the thrush and the robin, there is more singing after the breeding season than before or during the breeding season. We are shown, too, why these birds, and especially the thrush, so often sing in the winter: the supply of worms on lawns and in gardens being habitually utilized by both, and thrushes having the further advantage that they are strong enough to break the shells of the hibernating snails: this last ability being connected with the fact that thrushes and blackbirds are the first among the singing birds to build. It remains only to add that the alleged singing of males against one another with the view of charming the females is open to parallel criticisms. How far this competition happens during the pairing
