Gadwall
Mareca strepera
The Gadwall is a medium-sized dabbling duck, slightly smaller and more slender than the Mallard. In breeding plumage, the male exhibits a fine grey vermiculated pattern, a black rump, and a distinctive white wing speculum. It prefers nutrient-rich, still waters with abundant submerged vegetation and dense shoreline cover.
Details
Identification
White wing speculum (both sexes), male with black rump and grey body, female with orange-sided bill.
Social behavior
Gregarious outside the breeding season, often forming flocks with other dabbling ducks; more territorial during breeding.
Diet
Primarily herbivorous; feeds on leaves, stems, and seeds of aquatic plants as well as algae, supplemented by insects.
Hunting strategy
Dabbling in shallow water, filtering at the surface, and occasional short immersion of the head.
Overwintering
Migration to ice-free regions of Central and Southern Europe; utilizing large lakes and coastal waters.
Ecology
Ecological role
Important consumer of aquatic plants; acts as prey for predators and disperses plant seeds.
Natural predators
Red fox, brown rat, Western marsh harrier, Northern pike (for chicks), various mustelid species.
Competitor species
Mallard, Eurasian Wigeon, Red-crested Pochard.
Ecosystem service
Support of biodiversity through endozoochory (seed dispersal) and nutrient cycling.
Threats
Loss of wetlands, disturbance from recreational activities, changes in aquatic vegetation.
Scientific profile
Morphology & ID
Breeding plumage
The drake in breeding plumage features fine grey vermiculation on the body, a distinct black rump, and a pure white wing speculum. The female is inconspicuously patterned in brown and beige but also possesses the diagnostic white speculum.
Non-breeding plumage
In eclipse plumage, the drake closely resembles the female but is usually slightly greyer on the back and retains the high-contrast white wing speculum and often darker tones on the rump.
Juvenile plumage
Similar to the female, but with narrower, darker feather fringes on the upperparts; the white wing speculum is often less extensive or less clearly defined.
Sexual dimorphism
Distinct in breeding plumage; drakes with contrasting grey-black plumage, females cryptically colored in brown. Reduced in eclipse plumage but distinguishable by bill and plumage details (speculum).
Distinguishing features
The most important feature is the white wing speculum, which is not as pure white in any other native dabbling duck. The drake also has a conspicuously black rump that contrasts sharply with the grey of the body.
Confusion species
Mallard (Anas platyrhynchos): Female very similar but has a blue speculum. Common Teal (Anas crecca): Significantly smaller with a green speculum. Gadwalls appear overall more delicate and have a steeper forehead.
Bill
Drake: Dark grey to black, often with a fine pale edge. Female: Dark with orange lateral margins, similar to the Mallard but usually narrower and more delicate.
Vocalization
Song
No classical song; courtship calls of the drake are deep, belching 'rhek-rhek' sounds or a short, whistling 'piu'.
Call
The female utters a high-pitched, repeated 'quack' that often drops in pitch and is faster than that of the Mallard.