The greater scaup (Aythya marila), just scaup in Europe or, colloquially, "bluebill" in North America, is a mid-sized diving duck, larger than the closely related lesser scaup. It spends the summer months breeding in Alaska, northern Canada, Siberia, and the northernmost reaches of Europe. During the winter, it migrates south to the coasts of North America, Europe, and Japan.

Drake greater scaup are larger and have more rounded heads than the females; they have a bright blue bill and yellow eyes. Their heads are dark, with a green gloss; the breast is black, the belly white and the wing shows a white stripe. The females are mostly brown, again with white on the wing. They have dull blue bills and white on the face.

Greater scaup nest near water, typically on islands in northern lakes or on floating mats of vegetation. They begin breeding at age two, but start building nests in the first year. The drakes have a complex courtship, which takes place on the return migration to the summer breeding grounds and concludes with the formation of monogamous pairs. Females lay a clutch of six to nine olive-buff colored eggs. The eggs hatch in 24 to 28 days. The down-covered ducklings are able to follow their mother in her search for food immediately after hatching.

Greater scaup eat aquatic molluscs, plants, and insects, which they obtain by diving underwater. They form large groups, called "rafts", that can number in the thousands. Their main threat is human development, although they are preyed upon by owls, skunks, raccoons, foxes, coyotes, and humans. Greater scaup populations have been declining since the 1980s; however, they are still listed as a species of least concern on the IUCN Red List.
Greater Scaup
Date Location Count
2019-09-10 14:55Chestertown--Wilmer Park1
2019-09-19 13:03Silver Lake
2019-09-15 06:06Jamaica Bay Wildlife Refuge--East Pond1
2019-09-14 08:27Seneca Lake SP1
2019-09-15 10:45Long Point--Tip16
2019-09-18 08:02Long Point--LPBO Old Cut Field Station13
2019-09-15 15:20Fair Haven Beach SP1
2019-09-15 16:19Moses H. Cone Memorial Park--Bass Lake1
2019-09-12 16:05Hamilton--Van Wagner's Beach (Lakeland Centre)2
2019-09-19 14:58Hamilton--Windermere Basin1
2019-09-15 08:43Hamilton--Tollgate Ponds1
2019-09-21 06:55Rondeau Provincial Park (general location for observations within the park)1
2019-09-15 07:20Point Pelee National Park (general location for observations within the park)10
2019-09-21 11:02Tommy Thompson Park7
2019-09-17 17:15Toronto--Colonel Samuel Smith Park1
2019-09-19 14:10Presqu'ile Provincial Park--Owen Point1
2019-09-15 14:30Strathroy--Sewage Lagoons5
2019-09-13 07:21Moonstone Beach Rd.1
2019-09-21 10:10Essex Sewage Lagoons (western)1
2019-09-15 08:15Sarnia--Wawanosh Wetlands4
2019-09-12 07:55Kettle Point2
2019-09-20 08:58Barrie--Minet's Point2
2019-09-21 08:07Kincardine--Sewage Lagoons1
2019-09-21 13:40Inverhuron Sewage Lagoon1
2019-09-11 06:18Charlotte Town Beach3
2019-09-16 06:06Monomoy NWR--South End2
2019-09-16 17:40Monomoy NWR--Big Station Pond1
2019-09-21 09:16Etang, St-Louis-de-Gonzague3
2019-09-17 17:50Sablière, St-Lazare1
2019-09-08 13:14RN Baie-Missisquoi2
2019-09-11 11:56Quai, La Prairie4
2019-09-11 13:50Houghton Lake Sewage Ponds1
2019-09-10 14:45Baie-du-Febvre (station d'épuration, étangs & Route Janelle)5
2019-09-09 08:45Waukegan Yacht Club Marina1
2019-09-15 10:46Pointe de Maizerets1
2019-09-16 13:20Station d'épuration, Montmagny1
2019-09-15 12:12Quai, Montmagny1
2019-09-20 07:24Whitefish Point25
2019-09-09 11:45Seney NWR5
2019-09-08 18:12Chase Place1
2019-09-19 10:25Battures, Kamouraska2
2019-09-18 16:32Moncton--Bell Street Marsh (Wilson Marsh)1
2019-09-12 08:21Atholville--Station de Pompage et Marais (pump station and marsh)4
2019-09-08 12:20Dalhousie--Station d'épuration (sewage ponds)14
2019-09-08 10:57Plage Champlain1
2019-09-15 12:26Stephenville Crossing--Pond S of Main Gut61
2019-09-14 16:13Elk Island NP--Admin Area1
2019-09-10 07:10Nakusp - mouth of creek and adjacent lakeshore1
2019-09-17 14:30Grande Prairie--Crystal Lake10
2019-09-19 10:10Grande Prairie--Muskoseepi Park (Reservoir)9
2019-09-15 09:40Ferguson Lake4
2019-09-20 07:40Kelowna--Alki Lake landfill5
2019-09-17 15:13Kelowna--mouth of Mission Creek1
2019-09-11 15:47Fort St. John--north sewage lagoons1
2019-09-14 17:30McNary NWR--HQ14
2019-09-15 11:00Lake Pateros2
2019-09-15 09:07Priest Rapids Forebay (Grant Co.)25
2019-09-14 09:15Eaglet Lake21
2019-09-15 10:19Shelley sludge lagoons9
2019-09-13 12:45Skagit WMA--Wiley Slough/Wylie Rd1
2019-09-19 09:55Lake Sammamish SP1
2019-09-19 10:00Samish Flats--West 908
2019-09-12 14:37Skagit WMA--Hayton Reserve1
2019-09-13 17:00Skagit WMA--Jensen Access1
2019-09-13 07:45Tsawwassen Ferry Terminal Jetty1
2019-09-20 09:20Iona Island--South Jetty4
2019-09-15 06:45Eagle Lake, Chilcotin3
2019-09-14 08:40Roberts Creek Jetty1
2019-09-16 07:15Three Crabs7
2019-09-10 18:29Dungeness NWR--Harbor side2
2019-09-16 06:45Victoria Golf Course (restricted access)1
2019-09-19 12:05Patricia Bay3
2019-09-16 14:42Ediz Hook1
2019-09-16 17:50Englishman River Estuary--Plummer Rd side6
2019-09-14 16:32Englishman River Estuary (general)4
2019-09-14 15:02Pillar Point Recreation Area6
2019-09-19 11:42Deep Bay1
2019-09-17 14:09Neah Bay--town and bay only1
2019-09-18 12:35Grays Harbor NWR3
2019-09-20 11:59Tokeland -- marina10
2019-09-08 09:30Ross Lake Provincial Park, Hazelton7
2019-09-15 14:24Ocean Shores--Damon Point6
2019-09-13 10:49Ocean Shores -- Pt. Brown Jetty25
2019-09-09 10:29Tule Lake NWR--Auto Tour and Sump 1A1
2019-09-15 09:34Warrenton Sewage Ponds (restricted access)2
2019-09-15 16:58Veterans Park--Klamath Falls1
2019-09-18 10:50Wingwatchers Lake Ewauna Nature Trail1
2019-09-16 18:30Ucluelet--Amphitrite Point3
2019-09-09 11:20Boiler Bay State Wayside5
2019-09-08 07:07Moss Landing Harbor--Jetty Rd & north harbor1
2019-09-20 07:00Teslin Lake--Teslin Lake Bird Observatory2
2019-09-17 07:45MLK Jr. Regional Shoreline3
2019-09-21 07:50MLK Jr. Regional Shoreline--Arrowhead Marsh1
2019-09-16 13:30Wedderburn Oxidation Ponds1
2019-09-19 12:47Albany Mudflats1
2019-09-20 08:50McLaughlin Eastshore SP--Albany access
2019-09-10 15:00Reykjavík--Tjörnin pond5
2019-09-13 11:00Rauðavatn3
2019-09-20 16:50Hamilton Wetlands8
2019-09-18 15:32Selfoss--ræsi12
2019-09-17 11:01Laugarvatn1
2019-09-11 17:32Whitehorse--sewage ponds--long-term storage pond (restricted access)6
2019-09-13 14:35Langidalur--tjarnir við Móberg (ponds)
2019-09-13 17:00Reykjadalur--Hólkotstjörn3
2019-09-08 15:49Lón--suðurhluti (south part)2
2019-09-08 14:49Skjálftavatn lake
2019-09-14 12:06Sulphur Lake11
2019-09-14 14:32Nes--Þveit30
2019-09-14 08:47Barter Island (Kaktovik)5
2019-09-11 09:17Tanana Lakes Recreation Area22
2019-09-17 16:15Colville River Delta--Helmericks' (Restricted)(Anachlik Is.)17
2019-09-15 11:00Nenana (town)(MP A305 Parks Hwy)2
2019-09-20 09:23Spenard Crossing2
2019-09-18 16:56Westchester Lagoon1
2019-09-11 19:30Potter Marsh (MP A9.4 to MP A11.5 Seward Hwy)2
2019-09-13 19:12Anchorage International Airport32
2019-09-15 15:00Kasilof--Kasilof River Mouth2
2019-09-19 07:20Anchor Point4
2019-09-16 11:00Isle of Mull
2019-09-17 08:39Loch Mallachie1
2019-09-17 15:45Collennan Reservoir and Aught Wood1
2019-09-21 13:02Musselburgh--Levenhall Links1
2019-09-15 15:53Bethel--Sewage Ponds3
2019-09-19 14:18Bethel--H-Marker Lake2
2019-09-18 17:42Attenborough NWT Nature Centre and Reserve3
2019-09-20 09:15Gambell (general area)3
2019-09-08 06:25Sheringham--Seawatch1
2019-09-09 15:33Izembek NWR--Swan Lake30
2019-09-19 14:01Tåkern birding tower1
2019-09-14 14:30Biesbosch1
2019-09-15 09:00St. Paul Island (Pribilof Islands-Bering Sea)5
2019-09-19 12:30Fehmarn--Wallnau-Fehmarn (Wasservogelreservat)4
2019-09-19 07:15Falsterbonäset--Nabben1
2019-09-19 07:00Falsterbonäset2
2019-09-17 11:19Smygehuk2
2019-09-18 14:52Ottenby--södra udde1
2019-09-14 16:46Poosaspea Neem25
2019-09-19 10:15Rezerwat Mewia Łacha (Seagull Shoal Reserve)--East Side2
2019-09-20 08:45Adak Island (Andreanof Islands-Aleutian Is.)35
2019-09-08 08:00福岡市--和白干潟 (Fukuoka--Wajiro tidal flats)1