Mallards—Where Have All the Males Gone?
With the songbird breeding season winding down, let’s talk about waterfowl for a moment. The Mallard is the most familiar and widely distributed duck in North America. Ducks are generally classified in two ways, based how they forage for food in the water. “Dabbling” ducks, such as the Mallard, feed on the surface or “tip up,” with their tails in the air and their heads underwater, to grab vegetation below the surface. “Diving” ducks such as mergansers and grebes dive and chase food—typically fish and crustaceans—underwater. Except for the Muscovy Duck, all domestic species of duck can trace their ancestries to the Mallard. In fact, as breeding goes, the Mallard is one of the most inter-species “promiscuous” breeds, hybridizing easily where ranges overlap with American Black Duck, Mottled Duck, American Wigeon, Northern Pintail, Gadwall—as well as city park pond favorites such as the large domestic Long Island and Muscovy Ducks. (Above is a photo of a Mallard x Northern Pintail that we saw on a Christmas Bird Count in Salida a couple of years ago.) Its scientific name (Anas platyrhynchos) reflects its prominent, broad bill—from Latin for “duck” (anas) and Greek for “broad” (platus) and “snout or beak” (rugkhos). The common name derives from the old French “maslard,” meaning a wild drake. And speaking of drakes—did you know that a male duck is called a “drake;” a female, a “hen;” and the young (no surprise here), “ducklings”?
The Colorado Breeding Bird Atlas found Mallards breeding in every county and in all habitats across the state except alpine tundra and waterless prairies. Pairs generally form in the winter, so migratory Mallards arrive on their breeding grounds early and ready to breed. (Not all of Colorado’s Mallards migrate; some stay in more urban areas here as long as open water is available. When lakes freeze, they may temporarily move to flowing rivers and streams. These locals too start staking out breeding areas early.) Hens lay 1-13 eggs (typically, 8-9); the incubation period is 23-30 days. Ducklings are precocial, hatching fully covered with down. They are moving competently around the nest in about 12 hours. Ducklings usually leave the nest as a group on the morning after hatching, if the weather is decent—13-16 hours after hatching—with the hen leading the way. Only the hen cares for the ducklings, brooding them for about two weeks. They begin pecking at dark spots and small objects as soon as they leave the nest. In the first month, ducklings eat mostly animal foods (e.g., invertebrates, small crustaceans, mollusks, fish eggs), catching these morsels on the water’s surface or on land. In the second month, they move to feeding below the surface—dabbling and tipping up. In Colorado, the peak time for laying eggs is in mid-May. So any ducklings that Greenwood gets late in the summer most likely reflect pairs that renested after losing a clutch to rising water levels or depredation. In 2014, Greenwood took in 23 adults and a whopping 98 ducklings! (Because Mallards leave the nest so quickly, the normal distinctions of “nestling” and “fledgling” don’t really apply here.)
This time of year, Mallard drakes undergo a dramatic, rapid, and complete molt, which lasts only briefly in late summer. As a result, they are extremely vulnerable to predators because they can’t fly without their flight feathers. Interestingly, they seem to have evolved to do what the females do for most of the year, merging safely into the background with drab brown feathers. But even in this “eclipse” plumage, as it’s called, you can differentiate males from females by their bills. Year-round, females have orange bills with dark gray or black spotting while males have yellow or yellow-green bills. Here’s a photo of the familiar Mallard hen (right) and drake in breeding plumage. Compare this—especially the bills—with a drake in eclipse plumage. So if you spot a flock (or a “raft,” a term for a group on the water) of drab-looking Mallards in late July through mid-September, take a moment to check their bills. You may find an “imposter” drake or two mingling among the ladies.