Like other waterfowl, mallards undergo a series of molts or "feather changes." The male bird usually leaves the female after the eggs have been laid and retires to the seclusion of the marsh where he undergoes a complete molt from the green head, white neck-ring, and rusty colored breast to a drab-colored, brown plumage not unlike the female. He is completely flightless at this time. Almost immediately another molt, involving only the body feathers begins, and by mid-October most adult males again sport the brilliant "courtship" plumage. As soon as the female is finished rearing the young, she, too, undergoes a complete molt, including her flight feathers which must be regrown before the southward migration in mid-September can begin. Unlike the male, which goes from one molt to another within two months, the female mallard retains the plumage acquired in late summer until the following spring when the body feathers are changed.
Migratory mallards from Ontario, Quebec, and the northeastern states begin arriving in Connecticut during October. Some of these remain for a while and then continue south while others remain for the winter. Few mallards come from the mid-continent to Connecticut. Many mallards overwinter in park settings and are especially attracted to artificial feed which may do more harm than good. Feeding waterfowl may result in high numbers of birds concentrating in small areas, creating crowded conditions and competition among birds. In addition, waterfowl may become more susceptible to the spread of disease and less likely to migrate when the weather turns harsh.