The Greater Scaup is the larger, more northern of the two "bluebill" diving ducks, and in Michigan it is especially a bird of the Great Lakes, where great rafts gather on open water in migration and winter. The drake shows a dark head with a faint green gloss, a pale gray back, a black chest, and a golden eye, while the hen is brown with a crisp white patch at the base of the bill. A rounded, smoothly domed head and larger size help separate it from the very similar Lesser Scaup.
Greater Scaup breed on the Arctic and boreal tundra and come south to winter on large bodies of water, favoring the Great Lakes and big inland lakes over the smaller, more sheltered wetlands that Lesser Scaup will also use. They dive to feed on mollusks and other bottom invertebrates. Sorting Greater from Lesser Scaup — by head shape, gloss color, size, and the amount of white in the wing — is one of the enduring identification challenges of the state's cold-season waterfowl.
Dives to feed on mollusks — a major part of its diet, especially in the Great Lakes — along with aquatic insects, crustaceans, and some aquatic plants. It forages in rafts on open water, diving to the bottom of lakes and bays for its prey.
The Greater Scaup is larger with a smoothly rounded head that often shows a greenish gloss, and in flight it shows more white running out along the wing. The Lesser is smaller with a peaked, slightly angular head and typically a purplish gloss. The differences are subtle.
On the Great Lakes and large inland lakes, especially in migration and winter, where big rafts gather on open water. It favors larger, more open water than the Lesser Scaup often uses.
No. Greater Scaup nest on the Arctic and boreal tundra and come to Michigan only as migrants and winter visitors on open water.
Immatures resemble the brown female with a broad white face patch, and young males show a blotchy mix through their first winter. Look for the rounded head and broad black bill tip at any age.
A raft, like other diving ducks. Winter rafts on Lake Michigan and Lake St. Clair often mix Greater and Lesser Scaup, which is why scanning the edges of a raft is worthwhile.
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