Ruddy Duck

About the ruddy duck

The ruddy duck (Oxyura jamaicensis) is one of six living species of stiff-tailed duck in the genus Oxyura. Its scientific name comes from Ancient Greek oxus, "sharp," and oura, "tail," a nod to its long, stiff tail, which it holds cocked upward — and jamaicensis, "from Jamaica," referencing the specimen used in its original description. The species has also picked up the nickname "butterball," a reference to its short, stout build, which makes flying and walking upright look awkward.

It's a small, compact duck with a stout, scoop-shaped bill, a slightly peaked head, and a fairly short, thick neck. The male has a blackish cap that contrasts sharply with bright white cheeks. In summer he wears a rich chestnut body with a bright blue bill; in winter he turns dull gray-brown above and paler below, with the bill fading to dull gray. Females and first-year males are brownish year-round, resembling the winter male but with a blurry stripe crossing the pale cheek patch. In flight, the ruddy duck shows solidly dark wing-tops, and on average the female is smaller and lighter than the male.

The bill's scoop shape is built for underwater foraging, and the species is a strong swimmer even though taking flight is comparatively laborious — ruddy ducks rarely fly, and when they do it's with a fast wingbeat low over the water. An unusual internal feature is the trachea, along with inflatable air sacs and esophagi, which the birds use in courtship displays.

The ruddy duck was formally described in 1789 by German naturalist Johann Friedrich Gmelin, who placed it in the genus Anas based on a "Jamaica shoveler" specimen described a few years earlier by English ornithologist John Latham. It was later moved to Oxyura, a genus established in 1828 by French naturalist Charles Lucien Bonaparte. The closely related Andean duck was once considered the same species, but since that split the ruddy duck is monotypic, with no recognized subspecies.

Behavior and diet

Ruddy ducks are not especially vocal for most of the year, but become more so while courting and raising young. Males give short "aa-anh" calls in bursts; females have a higher-pitched "raanh" used with their brood, plus squeaks when chased by males and hisses toward intruders. Courtship typically begins on the breeding grounds rather than on wintering grounds, which sets the species apart from many other migratory ducks. Pairs can act aggressively toward each other one moment and be loafing calmly side by side minutes later.

The signature courtship behavior is called "bubbling": a male beats his lower mandible against his breast hard enough to churn up swirls of bubbles in the water, orienting his body laterally toward a female he's courting or facing a rival directly when the display turns aggressive. Nests are built by the female from grass in dense marsh vegetation near water, and a typical brood holds 5 to 15 ducklings. The female incubates for 23 to 26 days while her mate stands guard, but males take no part in actually raising the young. Ducklings become capable of flight within a month or two, and because they gain independence quickly, they often wander away from the rest of the brood before then. Females have also been observed practicing brood parasitism, laying eggs in other ducks' nests, though it isn't clear what drives the behavior.

Feeding happens mostly underwater, where ruddy ducks forage by straining food from the substrate, sweeping the bill side to side while opening and closing the mandibles to catch food while filtering out sediment. Because this stirs up the water, they locate prey by touch rather than sight, using sensory endings concentrated at the bill tip. The diet leans heavily on plant matter such as seeds and roots, along with aquatic insect larvae and pupae, small mollusks, and crustaceans like bivalves and amphipods; animal food makes up a larger share of the diet in winter. When searching for scattered food patches, ruddy ducks tend to revisit sites that were previously productive more often than chance would predict.

Range and habitat

Ruddy ducks breed in marshy lakes and ponds and are migratory, wintering in coastal bays and unfrozen lakes and ponds. Outside their native range, ruddy ducks were introduced to the United Kingdom in the 1940s. Escapes from wildfowl collections in the late 1950s helped the species become established there, and it later spread into continental Europe.

Conservation status

The ruddy duck is listed as Least Concern (LC) and faces no described threat within its native range. Outside the Americas, however, it is considered a highly invasive species. In Britain and parts of Europe, its aggressive courtship and its willingness to interbreed with the endangered native white-headed duck raised concern among conservationists, particularly in Spain, and led to a controversial culling program. By March 2012, a UK cull supported by the RSPB had killed 6,500 birds; by early 2014, the cull had reduced Britain's ruddy duck population to roughly 20 to 100, down from a peak of about 5,500 in 2000. Since 2016, the species has been included on the European Union's list of Invasive Alien Species of Union Concern, which bars its import, breeding, transport, sale, or intentional release anywhere in the EU.