Ruddy Duck

• Its courtship is more elaborate and more striking than that of the white-headed duck, and the females of that species seem particularly drawn to it: that is the root of the hybridisation problem.
• It reached Europe from a British collection: escapes and releases in the early 1950s, first wild breeding in 1960, and exponential spread ever since.
• It appears on the GEIB list of the twenty most damaging invasive species present in Spain.
• It is listed in the Spanish Catalogue of Invasive Alien Species (Royal Decree 630/2013). It reached Europe from collections in the United Kingdom and was first recorded in the Iberian Peninsula in the winter of 1983-84. Its problem is not competition but hybridisation: in 1991 the first hybrid with the white-headed duck, an endangered native species, was detected, and since then every bird and hybrid found is systematically removed.

Skeleton type

Vertebrate - internal bony skeleton (bird)

Habitat & environment

Shallow fresh water with abundant marsh vegetation. Native to western North America, with isolated populations in the Caribbean and Mexico; introduced into western Europe

Size at birth

The chicks fly between 50 and 55 days

Sexual maturity

12 months

Gestation / incubation

23 days

Litter / clutch size

8

Sources consulted: IUCN Red List; SEO/BirdLife (ficha y III Atlas: Onrubia y Gutiérrez-Expósito 2022); Catálogo Español de Especies Exóticas Invasoras (RD 630/2013); MITECO (ficha de especie invasora, 2013); Hughes 1996; Kershaw y Hughes 2002; Cranswick y Hall 2020 (WWT, Convenio de Berna); GEIB 2006, TOP 20 especies invasoras más dañinas de España; Urdiales y Pereira 1993

Best time: All year round; it is a partial migrant and travels by night