Sanderling (Calidris alba)

•   Appearance: Head and back mottled with white, black, and brown in breeding season (left) that turn to light gray in winter (right); white underparts; white stripe running through wings; black legs; long black beak
  • No significant difference between male and female in size or coloration
    • Sanderlings and other piper of Calidris genus are called “peeps”
• Length: 7 to 8 inches (about 1/2 foot)
• Wingspan: 13 inches (about 1 foot)
• Status: one of most common shorebirds, but populations are declining
  • Humans develop habitat into recreational areas
  • Sensitive to pollution and oil spills
• Habitat
  • In summer coastal tundras in Arctic Circle (northernmost Canada and Greenland)
  • In winter settle on sandy beaches from northern United States (both coasts) to southern South America (mostly along Brazil though)
  • Worldwide found on six continents (not on Antarctica)
• Diet
  • Small crustaceans, marine worms, mollusks
  • Run down beach after waves recede to snatch invertebrates left behind
  • Probe wet sand for burrowing prey
  • While running, sanderlings may skim food from tide pools, pick up prey moving on ground, or snap at flying bugs
    • Eat insects such as crane flies, mosquitoes, beetles, butterflies, moths
  • In absence of prey, sanderlings eat grasses, mosses, and algae
  • During migration feed on horseshoe crab eggs

• Migration
  • Breed in tundra in arctic circle (High Arctic Canadian Islands, Greenland)
  • Wintering grounds vary significantly
    • West coast stop as far north as Alaska, east coast stop as far north as Newfoundland and Nova Scotia (Canada)
    • worldwide,can be found roosting on almost any temperate beach
    • May also overwinter beside freshwater bodies, but less common
  • Migrate above continental land to save time
    • Stop at bodies of water to rest
  • Major stopover at Chesapeake Bay where sanderlings eat horseshoe crab eggs
    • Sanderlings need high protein and fat content in the eggs to sustain their energy while they migrate, these jelly-like eggs are the only thing their exhausted bodies can digest during their long migration path
    • Large horseshoe crab fisheries in this area forces human competition with sanderlings during migration season – birds come in massive flocks
  • If approached by a predatory bird (such as a falcon), the entire sanderling flock takes flight in compact “ball” and flies erratically over a body of water
    • Individuals may also dive into the water to escape the predator
  • Average flight speed is 20-25 mph, top speed is about 40 mph
• Nesting
  • Year round, sanderlings roost in flocks with up to thousands of other birds
    • It is often impossible to count how many birds are present in one site
  • Usually have one mate per season, but in certain areas or certain years
  • Nesting sites vary from moist sites with lots of vegetation to well-drained clay/gravel slopes to tops of stony ridges
  • Usually choose exposed location within nest site that has little to no vegetation
  • Usually use pre-existing depression, but if none exist the females digs a new one
    • Lines nest with vegetation, twigs, and pebbles
  • Average brood is 3-4 green eggs with brown/black streaks
  • Within 24 hours after hatching, young leave nest to forage
  • Both parents may care for chicks, but chicks largely feed themselves on insects
    • Sometimes female leaves, so male protects chicks
  • If potential predator approaches nest, sanderlings will freeze until last second, then they creep away from nest and feign injury
  • Fledglings learn to fly at 17 days old
  • Juvenile sanderlings have checkered backs, look like non breeding adults but backs appear darker
  • Often do not return to breeding grounds for a year or two while maturing so they do not waste energy on long migrations – stay on wintering grounds
  • Average lifespan is about 10 years, but oldest sanderling was about 13 years old