Greater Scaup

How to find it

Check any Aythya duck near the coast closely, since this species prefers saltier water. Start with head shape: flat-topped with a green tinge points toward Greater Scaup, while a peaked, purple-tinged head is the regular Lesser Scaup. If the birds fly, watch how far the white wing stripe extends along the primaries. Be cautious with a female on the water, because she can be told apart safely only in flight or in the hand. Beginners should not expect this bird, as it has been recorded only once.

How to recognise it

In flight, the white wing stripe is the best clue. It reaches at least the middle primaries, while on Lesser Scaup it stops at the secondaries.

At rest, all plumages resemble Lesser Scaup, so head shape and colour matter:

- Flat-topped head with a green tinge.

- White flanks.

- Adult male: a rounder head with a green gloss and a whiter-looking back.

Lesser Scaup, the regular Costa Rican scaup, has a peaked head with a purple tinge and light gray flanks.

Females can be told apart safely only in flight or in the hand, so a female sitting on the water is best left as a scaup until the wing can be seen.

What it sounds like

Recording: Dan MacNeal, CC BY 4.0, source, read 4 Nov 2026.

Behaviour and diet

Outside the breeding season this duck is very sociable with its own kind. Across its range, flocks can reach 10,000 to 15,000 birds or more, and it rarely mixes with other species. It often lives in large floating groups called rafts.

It dives for food and feeds at sea in rough weather, rarely coming ashore except to breed. These habits describe the species as a whole. A Costa Rican source describes winter birds as solitary, which fits a country where the only record is of three birds.

Where it lives

The species uses ponds, lakes and muddy wetlands like those of Lesser Scaup, but it prefers brackish or salty water. That fits the one Costa Rican record, which comes from the coast, in the Gulf of Papagayo on the Nicoya Peninsula.

It is a full migrant, and Costa Rica is listed among its non-breeding countries, so any bird here would be a visitor far from its breeding grounds.

When to see it

The only record dates from mid-October 1974, during fall migration.

Similar birds

Lesser Scaup is the look-alike, and all plumages of the two resemble each other. Greater has a flat-topped, green-tinged head and white flanks, while Lesser has a peaked, purple-tinged head and light gray flanks. In flight, the wing stripe is the surest difference.

Names and lore in Costa Rica

The official Costa Rican Spanish name is Porrón Mayor, with Pato given as an alternate. It pairs with Porrón Menor for Lesser Scaup. Other Spanish-speaking regions differ: Spain uses Porrón Bastardo and Mexico uses Pato Boludo Mayor.

Status and conservation

The official Costa Rican list gives it status A (accidental), while globally it is rated Least Concern, though its population is decreasing.