Thursday, January 7, 2016

American Black Duck

A pair of American Black Ducks

     The American Black Duck (Anas rubripes) is not a very showy bird and is not common in our area. It is very similar to the common Mallard both in behavior and voice. These large ducks (23" and about 3 lbs on average) look like dark Mallard hens in appearance. They are drab and dark, with slightly lighter colored heads and eye stripes. Black Ducks have a violet-blue patch on their wing (called the "speculum") that is bordered in black, though this is not always visible. Mallard hens are lighter overall in appearance and the speculum is bordered in white when visible. 

An American Black Duck on the left with its violet speculum next to two Mallards with white-bordered speculums.

     Their scientific name Anas is Latin for "duck" while the specific name rubripes is Latin for "red-leg." After the first year, they do indeed have reddish legs, leading to one of their common names: "Redlegs." They are also sometimes referred to as "Black Mallards" and/or "Blackies." Males (drakes) have unmarked yellow bills while hens have dull olive beaks. Otherwise the sexes look very similar. Black Ducks are light colored under their wings, contrasting heavily against their darker bodies. This makes for a good field mark when these fast flying birds are in flight. 

As this Black duck opens its wings, you can see the violet speculum and the white flash under its wings. 

     Black Ducks are mostly Northern birds. They prefer to nest in Canada and wooded areas well North of us. They get rarer as you go West and do not migrate very far South. They will use both fresh and brackish wetlands in the warmer months, but tend to winter in brackish estuaries and bays, mostly along the Atlantic Coast. Blackies winter farther North than most other dabbling ducks, very reluctant to go South even as the water freezes over. Though very strong fliers, they do not stray very far South or West, but have been known to (rarely) reach Great Britain.
     Black Ducks are dabbling, or puddle ducks. They feed by dabbling along the surface and tipping up to reach food below the water. They rarely dive, though they are capable of doing so to escape danger or if wounded. Like all dabblers, Black Ducks can spring straight into the air, 8-10' when taking off, not needing to patter or run along the surface like most diving ducks need to do before flying. 
     Black Ducks pair up during the winter. They hang out in small flocks or pairs and favor coastal waters. While over 85% of their diet is vegetable matter in spring and summer, they consume much more animal matter in the fall and winter. Black ducks consume three times as much animal food as Mallards during winter. This is likely due to it being easier to find crustaceans and mollusks in the coastal waters they overwinter in. 
     Back on their Northern nesting grounds, Black Ducks prefer isolated, wooded, dark locations. They usually nest on the ground and near water. Hens, who raise their young on their own like almost all dabbling ducks, will often nest within yards of the previous year's nest. They lay from 6-12 buff colored eggs that hatch approximately 27 days after being laid. 
     Almost all the eggs hatch within hours of each other. The hen then usually waits until dark to lead her precocial ducklings to the water. They fledge in about 60 days and will breed the very next year.
     Black Ducks are among the most wary of dabbling ducks. Due to their strong flight, elusive nature, and reputation as good table fare, they were at one time a favorite of duck hunters. They are difficult to decoy and have keen eye sight. Since the early 1980's however, very strict harvest limits have been placed on them. 
     Black Ducks numbers have been declining steadily since the 1950's and these rules were put in place to help stabilize their numbers. The population now is believed to be half of what historical numbers originally were. Much research is being done as to why, despite conservation efforts, their numbers continue to decline, sponsored particularly by hunting organizations such as Duck Unlimited and Delta Waterfowl.
     The main theories as to why their numbers have dropped have to do with habitat loss and encroachment by Mallards. Black Ducks are believed to prefer darker and more isolated wooded wetlands. They are less tolerant of intrusion and wary of people. Their darker plumage provides good camouflage in these conditions. But these more isolated and wooded wetlands are of course now much rarer. So is the open coastal waters they prefer to winter over in.
     With the decline in wooded wetlands and because Mallards are much less picky about their habitat, the range of Mallards has crossed over more now so that it overlaps that of Black Ducks much more than it did in the past. So now Mallards compete with them for both food and nesting areas.
     Mallards also readily mate and hybridize with Black Ducks. Some research suggests that 4% of matings now are with Mallards rather than other Black Ducks. Further more, some recent research also suggests that many of these hybridizations result from forced copulation of Black Duck hens by male Mallards. Mallard drakes are aggressive in pursuit of hens, often ganging up on hens and sometimes even drowning them in their urge to mate. Hybrids of Mallards with many other species such as Black Ducks, Pintails, Gadwalls, Widegon, Shovelers, Teal, and Mottled Ducks are common. So it may be that Mallard matings with Black Ducks are swamping-out the less common Black Duck, helping to breed them out of existence, along with competition for resources. 

A Mallard-Black Duck hybrid below a normal Mallard hen for comparison. There was a hybrid Mallard-Domestic white duck hybrid in the same small flock.

     So although Black Duck numbers are not in any threatened status, it is something that conservationists are worried about and researching. If all goes well, Black Ducks have been known to reach the record age of 26 years and 5 months. For short video of them, check out the following:


     American Black Ducks may not be common or even that handsome, but these are interesting ducks in their own right. Let's hope that conservation efforts halt their decline and allow their numbers to once again recover. 

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