Greater Scaup, Aythya marila, is a species of diving duck found in unvegetated or sparsely vegetated land, river and lake, marine inlet and transitional water and coastal ecosystems. It breeds in northern Europe, and winters mainly in north-western Europe and the Black Sea. The species breeds in tundra, moorland regions and wooded tundra in the high Arctic, occupying small, shallow, freshwater lakes, pools and rivers with grassy shorelines and high densities of invertebrate life. It shows a preference for water less than 6 m deep (usually 2 m) for diving. The species winters on shallow coastal waters (Kear 2005) less than 10 m deep as well as sheltered bays, estuaries and brackish coastal lagoons. It is also found inland on large lakes and reservoirs during this season (European Red List 2015).

Aythya marila has a breeding population size of 1300-2500 pairs and a breeding range size of 52700 square kilometres in the EU27. The breeding population trend in the EU27 is Decreasing in the short term and Decreasing in the long term. Aythya marila has a winter population size of 151000-275000 individuals in the EU27. The winter population trend in the EU27 is Fluctuating in the short term and Decreasing in the long term.

The EU population status of Aythya marila was assessed as Threatened, as the species meets one or more of the IUCN Red List criteria for threatened at the EU27 scale.