The mallard is the most common and best-known freshwater duck in Britain, and is a resident species, breeding in suitable localities throughout the country; but the birds that breed and remain all the year are few in number compared to the migrants that come to us in winter from more northern regions. In the domestic state the mallard is, next to the fowl, the most abundant and familiar bird we possess. The tame duck differs from the mallard only in its heavier body and shorter wings, and in being polygamous instead of monogamous in its habits. The tendency to vary in colour is a result of domestication in all species. It was from observing the annual change in the plumage of the domestic drake that the discovery was made that ducks differ from other birds in the manner of their moult. The period of the moult does not coincide in the drake and duck; and this discrepancy in the sexes has caused ducks to differ in their breeding habits from all other birds. Thus, in most birds, male and female share the labours of incubation, and of rearing and protecting the young; and the moult, which is always a period of danger, during which the bird is obliged to go into hiding, takes place some time after the young are able to shift for themselves--in other words, the family tie is broken after it has ceased to be necessary; and the female of the mallard, and of other ducks, moult in this way. Not so the male. He is smitten by the change after the eggs are all laid and incubation begun; with the result that the marriage tie is dissolved just at the period when his help is most needed. This is one of the strangest things in bird history; for up to the time when the physical change begins the drake is not less loving and solicitous than any other male bird, and if by chance the moulting period is delayed, he continues to guard the nest and share the labours of incubation; so that we may say, without straining a metaphor, that the drake is forcibly torn away from his marital duties, just as the late-breeding swift or swallow is sometimes forced by an overpowering migratory instinct to abandon its helpless young in the nest. The action of the swift in leaving its helpless young to perish of starvation in the nest is painful to contemplate, since we are accustomed to look on the parental affection as the most powerful of all; and in this case there is a conflict between this emotion and another--the desire for another climate; and the last conquers, and the young are forsaken. In the drake it is not a case of a conflict between two emotions or two instincts, but of a physical change, which kills or makes nugatory the instinct and emotion; for it is certain that the moulting period in all species that, like the duck, change their whole plumage in a short time, is not only a period of danger, but of suffering. When the change comes the bird acts like the ‘stricken deer,’ and like animals afflicted with some fatal disease: he goes