Muscovy ducks have been introduced into urban and suburban areas in Florida where they often occur in high densities. These birds were illegally released primarily by private individuals for ornamental purposes or as pets. Muscovy ducks can be extremely prolific and local populations can increase dramatically in a short time. As a result, controversies frequently arise between residents who enjoy the birds and residents who consider them a nuisance.
Because this introduced, non-native species sometimes creates problems through competition with native species, damage to property, and transmission of disease, in 2010 the U.S. Fish and Wildlife Service revised its regulations concerning Muscovy ducks. FWC does not remove nuisance Muscovy ducks. Removal of ducks can be done by the landowner or by a hired nuisance wildlife trapper.
Historically, wild mallards (Anasplatyrhynchos) normally winter in Florida in widely scattered, small flocks and are seldom seen in large concentrations except in some of the northern counties. These wild birds migrate out of our state to northern breeding areas in the spring and are not present in Florida during the mottled duck breeding season.
However, captive-reared mallards are being unlawfully released by humans in large numbers in Florida. It is estimated that more than 12,000 mallards are purchased statewide from feed-and-seed stores and potentially are released each year. These domesticated mallards are being purchased by well-intentioned individuals and are being released on local ponds, lakes and canals for aesthetic reasons.
Currently, these domesticated mallards can be found year-round throughout Florida on water bodies at city and county parks, apartment and condominium complexes, and in other urban and suburban areas. They are not part of Florida's native wildlife and are causing problems. State biologists are observing more and more mixed flocks and mixed pairs in the wild and these feral mallards are mating with mottled ducks, producing a hybrid offspring. These hybrid offspring are fertile, which further compounds the problem. Every mallard released in Florida can potentially contribute to the hybridization problem and the result is that fewer and fewer pure-bred Florida mottled ducks are left each year. An estimated 7 to 12 percent of mottled ducks are already exhibiting genetic evidence of hybridization and biologists list this hybridization as the biggest immediate threat to the conservation of Florida's mottled duck.
Other Examples Of Mallard Hybridization
Mallard releases in other parts of the world have devastated local populations of closely related species.
New Zealand grey duck - Mallards did not occur in New Zealand naturally, but were released to provide hunting stock. Now because of hybridization, approximately 95 percent of the native gray ducks in New Zealand are hybrids.
Hawaiian duck - This endangered bird is most likely completely hybridized on the island of Oahu, and may be genetically intact only on the island of Kauai.
Meller's duck - This highly endangered duck occurs in Madagascar and the remaining birds are being hybridized by introduced mallards.
The situation in Florida with mottled ducks and feral mallards is comparable to these examples in that we have a small, isolated population of a subspecies that is closely related to the mallard.