Monday, December 17, 2018

Redhead Ducks

An aptly named Redhead Duck drake (male) on an inland lake in Alexandria, VA.

     Redhead Ducks (Aythya americana) are medium-sized (18"-22") diving ducks which visit the mid-Atlantic region in winter. Weighing between 1.5-3lbs, these are considered bay ducks, or pochards in some parts of the world, members of the duck tribe called Aythyini. We have 5 species of bay or freshwater diving ducks locally that are all winter visitors (Redheads, Canvasback, Ring-necked Ducks, and both Greater and Lesser Scaup), though there are some 16 species globally. Though often just called divers, pochards around the world (2 different Genera worldwide) share some similar traits. First of all, most do not inhabit oceans and swim using only their feet (which like other diving birds are placed well back on their bodies). Sea ducks use their wings as well as their feet when swimming. Most male bay ducks also have similar plumage patterns of dark patches with light colors, bright colored eyes, and very similar voices due to having the same voice box apparatus (called fenestrated bullae). They all share a common ancestor.
     Redheads are aptly named, the drakes (males) having a bright red head, along with a bluish bill with a black tip, and a black bib. The females are much drabber. They are sometimes confused with their slightly larger cousins the Canvasbacks, but they have a much more rounded foreheads. Like all members of the Genus Aythya, none have the metallic colorful wing feathers referred to as a speculum and have their feet (much more webbed than many other ducks) placed well back on their bodies. This makes them superb divers, but awkward on land. Like other diving ducks, Redheads need to run or patter along the water's surface before they can take off.

A partial raft of Redhead drakes and hens near Dyke's Marsh on the Potomac River.

     While considered diving ducks, they often do not dive very deeply and sometimes just dabble or feed on the surface like Mallards and other "puddle or dabbling" ducks. Aquatic vegetation makes up a good portion of their diets, but they will also feed on animal matter such as mollusks and crustaceans. This is especially true during their breeding season when they consume the most animal protein.

Aquatic vegetation, particularly in winter, makes up a good portion of a Redhead diet.

     Like other diving ducks, these do not normally nest around the DC region. The vast majority of them nest in the northern prairie pothole and Great Lakes regions. More of them nest within the U.S. as opposed to Canada than all the other diving ducks. They choose treeless wetlands with lots of emergent vegetation.
     Redhead nests are basket-like and lined with down. They are usually anchored to the surrounding vegetation. The hens lay between 9-13 pale buff eggs which take between 24-28 days to incubate. The drakes leave after incubation starts, hanging out in small bachelor groups where they molt and are flightless for a period of time. The young ducklings fledge from 56-73 days later, but the mother hen often leaves them before the young can fly, sometimes 2-4 weeks prior to obtaining flight.
     Redheads are well known for brood parasitism. This is an unusual reproductive practice where hens dump their eggs into other birds nests. While other ducks may do this, none to the extent of Redheads. These are usually other Redhead nests, but up to 10 other duck species have been documented as serving host to Redhead egg dumping. They've even been known to lay their eggs in such completely different birds such as American Bitterns and even raptors such as Northern Harriers (Marsh Hawks)! Now this is not always a successful strategy, and those who lay their eggs into nests that are not even ducks rarely survive. In some locales 50% of the eggs are dumped, often by young females who may not even build their own nests. That these ducks nest so close to each other facilitates this behavior as well.
     Redheads who dump into other Redhead nests have the best chance, and some of them don't dump eggs at all or dump only part of their brood. But those that dump into other duck nests may only have 30% success rate if at all. One abandoned nest had 87 eggs in it. The favorite host to dump their eggs into other than another Redhead are their close cousins the Canvasbacks. Perhaps partially due to the chance of being raised in a foster nest, Redheads may hybridize with other ducks, especially other divers like Ring-necks and scaup. If they hybridize with Canvasbacks, the young are actually fertile and can mate as well.
     We see Redheads during their migration. They spend the winter in the interior parts of the country more so than any other diving duck, though they can range as far south as Guatemala and the Caribbean. While we get some in our area, 80% of all Redheads winter in the Laguna Madre region of Texas and Mexico, where  winter flocks of hundreds are the norm. In our region, they tend to be mixed flocks with other ducks, especially other diving ducks, sometimes in small numbers and sometimes in very large rafts.

A Redhead swims away from a Canada Goose intent on stealing the food it just brought up during a dive.

     Populations of Redheads overall have been relatively steady since 1955, though these are well below historical levels. Population numbers tend to be over a million birds, making up about 2% of the duck numbers in North America. However some areas have had greater declines than others. The worst regional declines seem to be an 87% decline in the Great Basin region, and even worse a 99% decline in Idaho, but overall the populations seem to have been steady and readjusted to other areas.
     These declines are usually considered to be due to habitat loss and changes such as droughts. Hunting pressure on them is relatively low, as they make up less than 1% of harvested ducks. This despite their widespread nature and their mild taste (due to vegetable matter making up such a large portion of their diet). This is also surprising as they decoy very well, earning a nick name in some places as Fool Ducks, being easily tricked into hunting range. But game laws and conservation practices seem to make hunting losses negligible to the overall population.

A Redhead Duck drake preens its feathers among some of its Ring-necked duck cousins.

     In our area, look for Redheads mixed in with other ducks in large open waters. I seem to bump into good numbers mixed in with Scaup ducks along the shallow stretches of the Potomac. They may reach the age of 12 years or so, and the accepted record so far from a banded bird is 22 years. So when you're near open freshwater (though again they can tolerate salty bays and such as well) keep an eye out for large rafts of diving ducks. If you search those groups, you may be rewarded with seeing Redheads among their numbers before they head back to their normal breeding grounds in the late spring. I'll leave you with a short video clip from the Capital Naturalist YouTube Channel of a Redhead drake that showed up in Kingstowne Lake in Alexandria: