In truth, the size and coloration of ducks have nothing to do with where they call home. Physically, mallards produced in the northern reaches of the prairie provinces are no different from mallards that nest in southern Illinois. Part of the answer lies in a little-understood process known as the molt. Because their feathers become worn from abrasion and exposure, ducks periodically replace their plumage through a process called molting. They grow new wing feathers to improve flight, replace down feathers for better insulation and sprout new body feathers for waterproofing.
Drakes wear their colorful breeding plumage until they abandon their mates in early to mid summer.
They then move to large bodies of water that provide adequate nutrition and offer protection from predators during the three to four weeks they'll be flightless after shedding their wing and tail feathers. Hens abandon their broods as soon as the ducklings have fledged. Scientists believe all family ties are severed once the hens leave their young behind to seek molting waters. Radio-banded mallard hens in central California have been known to make molt migrations of up to 300 miles. While most hens complete the molt of wing and tail feathers before migrating south, some pintails and gadwalls have been known to wait until they reach the wintering grounds.