By Chuck Fergus
Pennsylvania ducks may be grouped into two types: diving ducks and puddle ducks. Diving ducks often spend much more of their time farther out from shore than puddle ducks. Both groups can be found on streams, rivers, lakes and marshes. This note covers 15 species commonly called diving ducks.
Diving ducks eat seeds and other parts of aquatic plants, fish, insects, mollusks, crustaceans and other invertebrates. They dive underwater to obtain much of their food. They have large broad feet, fully webbed and with strongly lobed hind toes, that act as paddles. Their legs are spaced widely apart and located well back on the body, improving diving efficiency but limiting agility on land. Their bodies are compact, and their wings have relatively small surface areas. While this arrangement helps their diving and swimming, it hinders their ability to become airborne. Instead of springing straight out of the water into flight, as puddle ducks are able to do, diving ducks must run across the water to build up speed before taking off.
Diving ducks, puddle ducks, geese and swans begin migrating north through Pennsylvania in late February. Each year there is a peak in migration, when ponds across the state are crowded with waterfowl. While this period varies from year to year, it often follows heavy nighttime rains in late March or early April.
Diving ducks nest in New England, Canada, Midwestern and prairie states, the Pacific Northwest and Alaska. Several species inhabit both the Eastern and Western hemispheres. Three species of mergansers (which, though not actually diving ducks, are usually grouped with them) breed in Pennsylvania's northern tier.
Beginning in winter and before heading north, and into spring, males in their brightly-colored breeding plumage vie for females. Courtship may include ritualized drinking and preening movements, posturing and calling. Copulation takes place in the water. Males and females form monogamous pairs that last until the female begins incubating eggs; then, the male leaves the area and usually joins a band of other males.
Nesting habits and habitats vary from species to species. Generally, female diving ducks lay 5-15 eggs in vegetation, tree cavities, or rock crevices over or near the water. Because females do not start incubating a clutch until they lay their last egg, young develop simultaneously and all hatch at about the same time.
Ducklings are covered with down, patterned with shades of yellow or brown to break up their body outlines. Their eyes are open, and they can swim and feed themselves soon after hatching. The group, called a brood, remains together until the ducklings can fly, usually 8-10 weeks after hatching.
Adults undergo a post-breeding molt, growing a new set of feathers. Males molt first; in all species, the male's bright nuptial plumage is replaced by drabber, less-conspicuous feathering. While their flight feathers are growing, ducks cannot fly; they keep quiet and stay hidden during this period of vulnerability.
Ducks are preyed upon by raccoons, foxes, mink, hawks and owls; young are also taken by snapping turtles. Crows, raccoons and skunks eat the eggs.
In Pennsylvania, the fall migration of waterfowl begins in late August, peaks in October, and ends in December. Some ducks winter in our state, but most go farther south. Diving ducks winter along the Atlantic and Pacific coasts, across the southern states and in Mexico and Central America.
Habitat is of prime importance to ducks. Wetlands originally covered some 127 million acres in the U.S., but today more than half of those acres have been drained and converted to farmland, or developed for housing and industry. Drought periodically dries up parts of remaining wetlands, affecting duck reproduction. Ducks are vulnerable to oil spills on coastlines where they winter or breed. Pesticides, heavy metals and industrial pollution also harm them, either directly or by killing food plants or animals.
The Canadian prairie provinces -- Manitoba, Saskatchewan and Alberta -- form the single largest breeding habitat for many duck species. Alaskan and Canadian arctic wetlands are crucial to geese, swans and ducks. Our southern coastal states form an important wintering ground.
By the early 1900s, unregulated market killing had decimated duck populations along the Atlantic seaboard. Today, waterfowl populations in the region are stable, thanks to modern law enforcement and habitat management and preservation. The U.S. Fish and Wildlife Service monitors waterfowl numbers. The service divides the United States into four administrative units called flyways (they correspond to four major migration corridors for waterfowl) and gives states within the flyways guidelines for setting hunting seasons and bag limits.
Duck hunting is a challenging, rewarding sport. To pursue waterfowl, today's hunter is required to buy a federal duck stamp and a Pennsylvania migratory game bird license, revenues are used to monitor waterfowl populations through surveys and to acquire wetland habitat. Many people other than hunters also enjoy waterfowl, observing and photographing these colorful, diverse birds.