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Future Concerns About Mottled Ducks

By Charles R. Sharp, Former Wildlife Biologist, Alabama Department of Conservation and Natural Resources 

Alabama’s Gulf Coast is blessed with an abundance of wildlife species. One such species that calls this region home is the mottled duck (Anus fulvigula). Often referred to as the “summer mallard” or “summer duck,” the mottled duck lives in the coastal marshes of Baldwin and Mobile counties. Mottled ducks generally inhabit the coastal wetlands from Texas to South Florida. Unlike many other waterfowl species, the mottled duck calls the Gulf Coast home throughout the year instead of migrating north during the spring and summer months.

Mottled ducks nest in the fresh and brackish marshes and bays along the coast. With the increase of development along the Gulf Coast, much of the nesting habitat used by mottled ducks is being negatively impacted. Industrial and residential development, as well as the silting in of thousands of acres of preferred nesting habitat, occurs each year. These coastal wetlands are fragile ecosystems that can be affected greatly by only slight changes in the system such as water level, turbidity and salt concentration. Fluctuations in any of these factors can be extremely harmful to the wetland vegetation necessary for nesting.

The grassy wetlands used for nesting also provide an abundant food supply. These dense vegetated areas hold a tremendous amount of aquatic insects, mollusks, crayfish and plant material that make up a large portion of their diet.

 

The mottled duck is very similar in appearance to both the mallard (Anus platyrhynchos) and the black duck (Anus rubripes). Dark, chocolate-brown plumage on its body with contrasting lighter brown coloring on its head make it very difficult to distinguish between the black duck and mottled duck. The mottled duck, although similarly colored, will be slightly lighter in color.

In recent years, the close genetic relationship between the mottled duck and the mallard has brought about another hazard to the perpetuation of the mottled duck. The mallard is a migrating waterfowl that normally returns to its breeding grounds in the prairie pothole regions of Canada and the northern United States, and the mottled duck breeds almost exclusively in the Deep South. There has been only minimal opportunity for these two species to cross breed and hybridize. That has changed over the last several decades. The introduction of pen-raised mallards, which tend to be non-migrating, into the mottled duck range is allowing these two species to have contact during the breeding season. The release of pen-raised mallards has provided the opportunity for the hybridization of these two species. The aggressive mating nature and the number of these pen-raised mallards being released into the wild have fueled growing concerns of waterfowl managers for the mottled duck population.

The mottled duck, like many other waterfowl species, needs the help of this nation’s many conservation groups and outdoor enthusiasts. Great amounts of waterfowl habitat along the Gulf Coast, as well as around the world, are lost daily. Continued loss of habitat and the increase of hybridization over time may result in critical population declines in mottled ducks.


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