The shoveler, of course, has a bill that is in a league of its own. Shovelers primarily eat aquatic invertebrates, and their extra-wide, flattened bill with well-developed lamellae helps them skim crustaceans and other invertebrates from the water’s surface.
There are distinct differences in bills between blue- and green-winged teal. During the nonbreeding period, blue-winged teal consume seeds, aquatic insects, and some vegetation, but green-winged teal primarily eat seeds, including a variety of grains. As a result, the bill of the blue-winged teal resembles a miniaturized shoveler bill, whereas the bill of the green-winged teal might be compared to the shape of a small pinky finger—the width of the bill is uniform throughout its whole length.
In contrast to mallards, two species of ducks common to bottomland hardwood forests, wood ducks and hooded mergansers, have bills that are quite specialized. The wood duck eats acorns, seeds of moist-soil plants, some vegetation, and aquatic insects. Its bill is shorter and narrower than the mallard’s because it specializes in grabbing acorns or cutting bulbs from wetland plants and swallowing them in pieces. Because the hooded merganser primarily eats small fish and aquatic invertebrates, its bill is long and narrow, resembling a pair of needle-nose pliers capable of demobilizing its prey.
The bills of diving ducks are also interesting. For example, canvasbacks use their stout, wedge-shaped bill to grub or rip tubers and roots of aquatic plants, whereas redheads are more like aquatic browsers and eat stems and leaves of submersed plants. As you might expect, the canvasback has a longer and heavier bill and a thicker, more muscular neck than the redhead.
We often see several species of geese in the same open green fields, but they are not necessarily eating the same foods. Snow geese uproot grasses and sedges to eat roots, rhizomes, and bulbs, while Canada geese shear off short grasses above ground. The bill of the snow goose is much higher than it is broad at the base, which gives the impression that the bird is smiling. The bill of a large Canada goose is stout but appears straight rather than curved like the bill of the snow goose. Although both geese eat waste grain, their bill adaptations evolved long before the advent of agriculture. Snow geese historically wintered along southern coastal wetlands and ate tubers and roots of marsh grasses and sedges. Long ago, Canada geese adapted to forage on seeds and herbaceous plants in river bottoms and probably in upland fields that contained short, new growth of green grasses. Today, agricultural fields are smorgasbords for these geese. Both species eat a variety of grain at specific times and places. However, Canadas still savor the stems of short green shoots, like wheat or barley, while snow geese grub the roots of these and other plants.
Nature has modified characteristics of waterfowl species so that they can exploit different types of foods. This allows them to coexist in the same habitats without much competition for food. Next time you are waterfowl hunting or just watching ducks and geese, study their modes of feeding and think about how they have developed great tools for accessing their favorite foods.
Dr. Brian Davis is a DU regional biologist based in Little Rock, Arkansas.