Common. Only scaup that breeds in Great Plains. Widespread winter distribution with preference for fresh water. Rarely in large flocks. Often seen in salt water after frozen out. ID: Compared to GRSC, LESC is roughly 10% smaller and looks slighter-bodied. Different head shape critical: peaked at rear crown (long crown feathers), giving a more balanced square-headed feel than GRSC (very difficult to judge on diving birds). Thin-necked. Shorter and more parallel-sided bill with black usually confined to nail. Purple-headed male scaup is usually LESC. However, LESC commonly shows green iridescence, particularly in winter. Flanks brighter and cleaner white through early winter in GTSC, LESC usually has brown mixed in white so doesn’t look as striking. Males average coarser barring on upperparts than GRSC, and browner on flanks. Female’s coloring essentially as GRSC. Young birds have darker eyes (paler in adults, both sexes), less white at base of bill and fewer gray feathers than older birds. In flight upperwing has white wingstripe on inner wing, contrastingly browner in primaries, but not always easy to see. GRSC has less contrast and usually appears more uniform. GRSC’s larger head is sometimes noticeable in flight. LESC has darker gray greater underwing coverts.