Western Sandpiper
Calidris mauri

Physical Description 

• Small birds, rather chunky and round in shape.
• Breeding males: Have black legs, a long thin black bill that slightly droops at the end, and black eyes. Rusty-brown and black mottled feathers on the back, a rusty head cap, and a white belly with dark streaks.
• Breeding females: Look like males, but are generally larger and have longer bills than males.
• Non-breeding adults: Have lighter feathers than breeding adults, more of a light brown or gray than a rust, with little streaking on the chest.
• Juveniles: Look like non-breeding adults with a whiter face and a more scaly looking feather pattern on the back. Have a black stripe down the center of the tail.

Range 

• Migrating: they migrate across most of western Canada and the United States.
• Non-migrating: they spend the winters on the coastlines of the US and Mexico, and, rarely, in the interior of Mexico.
• Breeding: they breed in northern Alaska and eastern Siberia.

Habitat

• Sandpipers nest on the ground near dry vegetation.
• They forage for food in tidal estuaries, coastal lagoons, shorelines, ponds, river deltas, and salt marshes.
• They always forage for food in very shallow water, often only a few inches deep.

Reproduction

• The male sandpipers make the nests and perform elaborate courtship displays for the females. Although the female looks like she is ignoring the male for several days, eventually she chooses the nest she approves of.
• The nest is made of dry willow leaves, birch leaves, grass, and lichens.
• All mating is monogamous, and about half of the same pairs nest together year after year.
• Both the male and the female will sit on the egg to keep it warm and both will help defend the nest.
• The female will leave before the chick hatches, however, leaving chick-rearing to the male.
• The female lays 2-4 eggs which are about 1.2 inches long.
• The chicks are born active and covered with down.

Diet

• When we see them in La Jolla Shores, they are eating aquatic invertebrates, such as crustaceans, mollusks, plankton, and marine worms.
• Sandpipers also slurp the frothy “biofilm,” a mixture of diatoms, microbes, organic detritus, and sediment.
• Females have longer beaks, so they hunt by probing in the sand. Males hunt visually, by pecking and gleaning. Males are often hunting in more dry, shallow sand.

Predators 

• Red foxes, arctic foxes, long-tailed jaeger birds.

Interesting Facts 

• Western sandpipers are one of the most abundant shorebirds in North America with a population in the millions.
• Western sandpipers migrate together in huge, spectacular flocks.

Sources: AllAboutBirds.org; Birds of North America.org; AnimalDiversity.org; Audubon Field Guide 

Photo: Thomas A. Blackman