Common Merganser

Mergus merganser

Sleek fish-eater with a serrated bill. Ferries chicks downstream on her back in single file.

Population: Approx. 1,700,000–2,400,000 mature individuals globally (2015 estimate, per BirdLife International / IUCN assessment); European population component ~134,000–206,000 mature individuals (66,800–103,000 pairs).
Habitat: Clear, fast-flowing rivers and large lakes in forested landscapes for breeding (nests in tree cavities); shifts to large lakes, big rivers, reservoirs, and sheltered coastal/estuarine waters in winter.
Fun fact: Female Common Mergansers sometimes form 'crèches' by combining broods, with one female recorded tending more than 70 ducklings at once.
Range: Holarctic distribution — breeds across northern North America (Alaska/Canada south into the northern contiguous US), and across northern Europe and Asia (including Scandinavia, the UK, and Siberia); northern populations migrate south to temperate latitudes for winter, while some populations are resident year-round.
Diet: Primarily fish, caught by diving and gripped with a long, narrow, serrated ('sawbill') bill; also takes mollusks, crustaceans, worms, aquatic insect larvae, amphibians, and occasionally small mammals or birds. Ducklings start on aquatic insects before shifting to fish around 12 days old.
Size: 0.65 m
Wingspan: 0.88 m
Lifespan: 13 years

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