I’ve had the good fortune to photograph both the eastern and western subspecies of Willet (Tringa semipalmata) in breeding plumage, the eastern in Florida and the western in Utah and Montana.
The image above shows the eastern subspecies; Tringa semipalmata semipalmata, in breeding plumage. This bird and another successfully reared young at Fort De Soto’s north beach in 2009. This bird is perched on a White Mangrove on June 21, 2009.
This image shows the western subspecies; Tringa semipalmata inornata, in breeding plumage perched on Rabbitbrush on Antelope Island State Park on June 6, 2012.
It is difficult to see the differences in the two subspecies but close observation shows that the bill of the eastern subspecies is thicker than the western and the bill of the western is slightly longer. The plumage patterns are also slightly different plus the white around the eye of the western seems more pronounced.