Greater Scaup is a mid-sized diving duck that occurs in Arizona almost exclusively as a winter visitor, typically arriving in late November and departing by early March. They concentrate on open waters—reservoirs, sewage ponds and marshes—most reliably within the lower Colorado River valley (Lake Mead through Lake Havasu and the Bill Williams River), where winter counts often list them as common. Outside this corridor, Greater Scaup are scarce in Arizona, with any records beyond the lower Colorado requiring photographic or written verification. In the field they usually form small flocks, often mixed with the more abundant Lesser Scaup, and can be separated by their rounder head, broader white wing stripe and slightly paler gray back.
