Distinguishing Characteristics

Medium-sized Calidris sandpiper (length 16–22 cm, mass 48–64 g; Holmes 1966a, Page 1974). In all plumages, look for black legs, relatively long, black, slightly decurved bill (especially tip), and slightly hunched appearance. Few obvious sex differences in plumages of North American birds. C. a. hudsonia males tend to have darker bellies and grayer faces than females (J. Jehl pers. comm.); male C. a. alpina has a pale grayish collar (Cramp and Simmons 1983). Females generally larger than males (Brennan et al. 1984, Cramp and Simmons 1983).

Striking differences between Basic and Alternate plumages. Alternate plumage distinguished by black belly, rufous cap, and bright rufous brown back; can be confused only with Rock Sandpiper (Calidris ptil-ocnemis) which also has black patch, but on lower breast instead of belly. Races vary in size and brightness of coloration (Hayman et al. 1986). Juvenal plumage more buff and scalloped; back also rufous brown, fewer brownish black splotches on belly; rarely seen in this plumage away from breeding grounds (photo in Paulson 1993). Basic plumage light brownish gray with diffuse brownish band of streaking on upper breast and white underparts. Very similar to Basic plumage of Curlew Sandpiper (C. ferruginea), but Dunlin lacks that species’ clear white rump. Purple Sandpiper (C. maritima) and Rock Sandpiper are similar in size but darker bodied and have short, greenish yellow to orange legs and bicolored bill. Western Sandpiper (C. mauri) and Semipalmated Sandpiper (C. pusilla) have similar Basic plumage but are smaller, have shorter bills, and are generally lighter in appearance.

In flight, Dunlin’s white wing-bar, white underwing, and black belly (Alternate plumage) are obvious; often gives a krree (NDW) or treep call (Cramp and Simmons 1983).