By Joyce C. Mazourek and Paul N. Gray

Many animals native to Florida are threatened by the introduction of non-native species into the state, and the mottled duck, sometimes commonly known as the Florida duck or the Florida mallard, is one of these. Introduction of breeding populations of a closely related species, the mallard, threatens the existence of Florida’s only endemic duck.

Both Florida’s mottled duck and the mallard are part of a worldwide group of about 20 species of ducks that are so closely related that they collectively are called the "mallard complex." However, when mottled ducks and mallards come in contact during the breeding season they create hybrid offspring that are different from either parent.

Florida’s mottled duck, one of the few non-migratory ducks in North America, lives only in peninsular Florida. The wild mallard, on the other hand, is a migratory bird that inhabits temperate zones of North America, Europe and Asia; it occupies Florida during the winter, returning north in the spring to breed.

The mottled duck is easily distinguished from the mallard - rather than the male being brightly colored and the female dull, both male and female mottled ducks are simply a mottled brown. Also, the speculum (a colored patch on the wing) is iridescent blue with bold white borders in mallards, but iridescent green and purple with, at most, a faint white border in mottled ducks. Adult male mottled ducks have a yellowish bill that distinguishes them from the females, whose orangeish bill has black blotches across the top and sides.

Historically, three members of the mallard complex naturally inhabited Florida: Florida’s mottled duck, the black duck and the mallard. Only the mottled duck bred here. Wild populations of the other two species returned north to breed, as noted by several 19th-century naturalists, like E.D. Scott, who wrote in 1888 that mallards were not abundant in the state and were winter visitors only.

A problem now has arisen for the mottled duck, and its cause can be traced to domesticated ducks.

Only two ducks in the world are truly domesticated: the mallard and the muscovy. Both have been selectively bred by humans, just like cats, dogs and livestock, to form distinct "breeds." As with other domestic animals, all domestic mallards are the same species even though their appearances vary greatly. They range from 2-10 pounds in weight and may resemble the wild, green-headed mallards or may be black, white, brown, blue or some combination of these. Most ducks found on canals and in parks are a breed of mallard, muscovy, or a mixture of both (yes, mallards hybridize with muscovy ducks too).

Since the early 1900s, private citizens have been purchasing domesticated mallards as pets or for hunting, and releasing them in local lakes, canals and parks throughout Florida. The problem with released mallards is that they become feral (domesticated and loose, living free in the wild) and establish breeding populations that, unlike wild mallards, do not migrate north in the spring. For this reason, breeding mallards are considered exotics in Florida, while migrant mallards are deemed a normal part of Florida’s bird life.

The domesticated breeders often leave urban an suburban areas and begin nesting in the surrounding natural habitats where mottled ducks prefer to nest. Sometimes, too, mottled ducks venture in from "wild" areas to nest near developed areas.

As a result, the mottled ducks and mallards interbreed. Florida’s mottled duck and the mallard are so genetically similar that they produce fertile offspring. Scientists are already detecting mallard genes in the mottled duck population and are concerned that interbreeding with mallards may lead to the demise of Florida’s mottled duck as a distinct entity.

This concern is well-founded. The American black duck typifies the interbreeding problem. In this instance, black ducks hybridize with wild mallards, which have expanded their range into black duck territory (northeastern United States and eastern Canada), primarily because of habitat alteration.

Their courtship displays are so similar that, oddly enough, male mallards may even be better than black ducks at attracting females. When mallard and black duck males compete to mate with the same female of either species, the mallard is more likely to successfully pair with the female. His attractive color and dominant behavior presumably give him an advantage over the dull-colored male black duck, resulting in hybrid offspring that usually look more like mallards than black ducks. About 5 percent (and as many as 30 percent in some areas) of black ducks in eastern North America exhibit obvious mallard traits, and hybridization appears to be increasing. 

The problem of mallard hybridization is widespread and serious. In New Zealand, introduced mallards are hybridizing with another member of the mallard complex, the grey duck. During the past 80 years, mallards have been released there to supplement wild duck populations for hunting, and now the proportion of pure grey ducks remaining is only about 5 percent of the grey duck/mallard population. In a very short time, New Zealand’s grey duck is expected to disappear from the wild. In Hawaii, the Hawaiian Duck National Wildlife Refuge no longer has pure Hawaiian ducks: the birds are mostly mallard. Virtually the entire population of the Mexican duck in the United States has been hybridized with mallards and may not persist, and in Madagascar, it appears that the Meller’s duck faces a similar future. All the above examples can be traced directly to human activities, especially the release of domesticated mallards. Fate will deal the same bad hand to the Florida mottled duck if current trends continue.

What can be done to help? Breeding mallards must be recognized as exotics in the state of Florida, and the release of additional mallards must be stopped. Release or relocation of ducks without a permit is a violation of Florida Statutes (click HERE to more). Unfortunately, most people are unaware of these rules and often do not understand why such a rule would exist. In addition to the hybridization risk, released mallards (and muscovies) often transmit diseases such as avian cholera and duck viral enteritis to wild waterfowl.

The American Association of Wildlife Veterinarians recognizes the hazards of introducing exotic species and has issued a resolution encouraging government agencies to limit populations of domestic waterfowl in the United States. In the dispassionate world of biological science, the control and eradication of exotics is sound conservation practice. However, eliminating feral mallards from Florida would distress many people who enjoy having them around their homes and in parks.

The U. S. Fish and Wildlife Service has written regulations that protect our nation’s waterfowl, but ironically, these regulations can be interpreted as protection for these Florida intruders. Even though it is obvious that feral mallards are not wild because they remain in Florida year-round, they are included under the same federal definition of "migratory birds", as wild ducks. Therefore, feral mallards, their nests and their eggs are protected under the Migratory Bird Treaty Act. This creates considerable confusion on the legalities of controlling feral mallards because Florida’s laws do not protect domestic ducks (F.A.C. 39-1.004(87). The Florida [Fish and Wildlife Conservation Commission] is in the process of addressing this situation and hopes to develop guidelines to deal with these difficult and conflicting issues.

Citizens can help now! Mallards should never be released or fed, especially those present in Florida during the summer. We also should encourage our neighbors not to release or feed mallards. Much of the battle for saving the mottled duck must be waged by spreading the word to people who do not know why releasing and supporting feral ducks in harmful. To some people, having Florida’s mottled duck hybridized out of existence may not be a concern. To people with more of an appreciation of the natural world, losing the mottled duck is akin to destroying an original work of art - it cannot be replaced. Ever.

Today, the future of Florida’s mottled duck is uncertain. Scientists can predict what will happen, but society must decide what does happen. It is up to us. Our generation is deciding if these ducks are to remain a part of our planet’s natural heritage. Hybridization is happening now.

Reprinted from the May-June 1994 issue of Florida Wildlife.

At the time of this writing Joyce Mazourek worked as a temporary technician for the Waterfowl Management Section and later pursued a master’s degree at the University of Missouri; Paul Grey was a biological scientist with the Waterfowl Management Section in Okeechobee.

Return to the Florida Mottled Duck page.

Return to the Mallards in Florida page.

Return to Florida's Waterfowl home page.

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