Ruddy Duck

This small, compact, stiff-tailed waterfowl exhibits a striking sexual dimorphism during the breeding season. Breeding males are easily recognized by their rich chestnut-red plumage, a velvet-black cap on the head, and conspicuously bright white cheek patches, which contrast with a wide, flat, scoop-shaped bill of an intense sky-blue coloration. Non-breeding males and females present a much duller, cryptic appearance, dominated by grayish-brown tones, a dark cap, and a distinct horizontal dark smudge crossing the pale buffy cheek. Adults measure between 35 and 43 centimeters in length, have a wingspan of 53 to 62 centimeters, and weigh between 310 and 795 grams. The long, stiff rectrices of the tail are often cocked vertically, creating an iconic silhouette that represents a diagnostic family trait of the Oxyurinae subfamily.

Geographical distribution: The native breeding range encompasses much of North America, extending from the subarctic regions of Canada through the United States and down into central Mexico, with resident populations also present in the West Indies. During the autumn migration, northern populations travel southward to winter in ice-free coastal waters, the southern United States, and parts of Central America. Furthermore, the species was introduced to the United Kingdom in the mid-20th century as an ornamental species, from where it spread to mainland Europe, establishing feral populations in countries such as Spain, France, and the Netherlands, where it is now classified as an invasive alien species subject to strict control.

Habitat: It primarily selects shallow freshwater wetlands, including marshes, ponds, lakes, and sluggish rivers featuring a dense fringe of emergent vegetation such as cattails (Typha) and bulrushes (Scirpus), which are essential for shelter and breeding. During wintering and migratory stopovers, its habitat preferences shift toward larger, open water bodies, including deep inland lakes, brackish estuaries, coastal lagoons, and even wastewater treatment ponds, where ice-free surface water is guaranteed.

Feeding: It is an opportunistic omnivore that secures its food almost entirely by diving to the bottom of wetlands and straining muddy benthic sediments through its specialized lamellate bill. Its diet consists largely of aquatic macroinvertebrates, particularly midge larvae of the family Chironomidae, but also includes aquatic beetles, snails, small crustaceans, and annelids. To complement this protein-rich diet, it consumes seeds, tubers, and vegetative parts of submerged aquatic plants, such as pondweed (Potamogeton) and coontail (Ceratophyllum).

Behavior: Highly aquatic and adapted for a life afloat, it is extremely clumsy on land because its legs are positioned far back on the body to facilitate powerful underwater propulsion. When threatened, this duck rarely takes flight, preferring to compress its plumage and sink slowly beneath the surface or swim away with only its head and eyes exposed. The male´s elaborate courtship display involves rapidly beating its bill against its inflated throat sac, producing a series of hollow tapping sounds and creating bubbles in the water, while raising its tail and performing short, rushing glides.

Nesting: It constructs a well-concealed, bowl-shaped nest woven from dry rushes and cattails, placed directly over water and anchored to surrounding emergent vegetation, often featuring a woven ramp to facilitate access. The female lays a clutch of 5 to 10 unusually large, chalky-white eggs with a rough, coarse texture. Incubation, which lasts between 21 and 26 days, is carried out solely by the female. Intraspecific and interspecific brood parasitism is a common reproductive strategy, with females frequently laying eggs in the nests of other waterfowl. The hatchlings are highly precocial and covered in thick down; they can swim and dive efficiently within hours of hatching, although they remain under maternal care until they fledge.

Conservation status: It is categorized as Least Concern (LC) on the IUCN Red List of Threatened Species, owing to its vast global population and extremely wide geographic range. However, in Europe, it is classified as an invasive species of high concern. Rigorous eradication programs are actively implemented to prevent hybridization with the globally endangered white-headed duck (Oxyura leucocephala), as such hybridization threatens genetic integrity and poses a major extinction risk to the native European species.