- Lifespan
- 12–15 years in the wild
- Size & Weight
- 48–56 cm, wingspan 75–85 cm; 750–1,100 g
- Habitat
- Coastal waters and large inland lakes, preferring deeper marine and freshwater areas where they can dive for food.
- UK Distribution
- Winter visitor and passage migrant to UK coasts, arriving August–September and departing April–May. Small breeding population in northern Scotland (Outer Hebrides), with the vast majority wintering in northern European waters.
- Diet
- Benthic invertebrates, particularly molluscs (mussels, cockles), crustaceans, and aquatic insects obtained by diving to the seabed.
- Prey
- Mussels, cockles, small crustaceans, chironomid larvae, other benthic invertebrates
- Predators
- Great black-backed gulls, white-tailed eagles, otters, foxes (on eggs and young)
- Mating Season
- April to July
- Breeding
- Clutch size 6–9 eggs; incubation period 27–28 days; single brood. Nests on moorland near water; females are cryptically plumaged.
- Behaviour
- Highly gregarious, often seen in large flocks on wintering grounds. Males are striking jet-black with bright yellow-orange bill; females are brown. Excellent divers, reaching depths of up to 20 metres.