Western Sandpiper

Bird of the Month: Western Sandpiper

By Andy McCormick

PC: Mick Thompson (Western Sandpiper)

PC: Mick Thompson (Western Sandpiper)

Scientific Name: Calidris mauri

Length 6.5 in

Wingspan 14 in

Weight 0.9 oz

AOU Band code WESA

The Western Sandpiper is part of the genus Calidris from the Greek kalidris which was used by Aristotle for a speckled waterbird.  Mauri is from Ernest Mauri (1791-1836) an Italian botanist and a friend of Charles Bonaparte (1803-1857), who named this bird for him.  They co-authored a book on Italian fauna.  The bird is the western counterpart to the Semipalmated Sandpiper Calidris pusilla and the common name designates this location.  Like the Semipalmated the Western also has partially webbed feet.  Piper is from the Latin pipare, to chirp (Holloway, 2003).  This sandpiper is one of a large group of small shore birds commonly called peeps or stints. 

The Western Sandpiper does not nest in Washington but is an abundant migrant in spring and fall.  The fall migration begins in late June and goes through September with some wintering birds seen along the southwest coast of Washington.  Identification of the peeps can be difficult and the overall gray coloration in the fall does not make it any easier to tell them apart.  The Western’s bill is moderately thick with a slight droop at the end, but not as much droop as the larger Dunlin Calidris alpina.  The Semipalmated has a shorter, straighter bill and since it is less likely to be found along the west coast in the fall and winter the odds favor seeing the Western.  The Least Sandpiper Calidris minutilla is the smallest of the four and has yellowish-greenish legs.   In fall the overall size, bill and legs are the best field marks to tell these peeps apart.  In breeding plumage the Western has a rufous crown, ear patch and scapulars. The Semipalmated has no rufous coloration but is brown and black instead.  The Least Sandpiper is the brownest of the three with brown on the breast as well.  

These adventurous birds breed in a gravel scrape in the western Alaska arctic tundra.  Three to four brownish eggs with dark brown spots are incubated by both parents for 21 days.  The chicks will walk from the nest shortly after hatching and fly in about 17-21 days.  Often the female will leave the nest just before or after the birds hatch and the male will be responsible for caring for the young.  The birds generally feed on insects, crustaceans and marine worms (Kaufman, 1996).   Recent research has found that they also get half of their daily energy from feeding on the biofilm that grows as a mat on the surface of mudflats and their ability to feed on this goo of microscopic bacteria is thought to be a reason for the species’ abundance even while North America is losing wetlands areas (Lovette in Ecology 89, 2008).  Despite their abundance special protection is needed at the Copper River in Alaska where nearly 90% of the total population of Western Sandpipers stops during migration.  In 1973 over 6.5 Million individuals were counted in April and May.