Ninety-seven percent of the Delaware Bay shorebirds are known collectively as the “big-four sandpipers”. They are the red knot, the sanderling, the ruddy turnstone, and the semipalmated sandpiper.

Red Knots
About half of the total population of red knots (about 100,000 birds) depend upon Delaware Bay’s horseshoe crab eggs as a food supply. This group makes up the largest concentration of the species in the Western Hemisphere, and they eat about 248 tons of eggs. The red knots reach the Delaware Bay after a 7,000 mile flight from Argentina, with the last part of the trip covering 5,000 miles apparently nonstop. One part includes a long stretch over open ocean. The bay is the only known stopover for the birds on their trip from coastal Brazil to the Arctic. From the bay they will fly 2,000 miles nonstop to their nesting grounds in the Arctic and Greenland.
The scientific name for this buff black backed bird is Calidris  canutus. It has the red color of a robin for its head and underparts. This particular shorebird is 9.5 to 10'' tall.

Ruddy Turnstone
The ruddy turnstone, or the Arenaria interpres , finds its horseshoe crab eggs by digging holes in the sand, exposing horseshoe crab eggs that have been buried there. It uses its beak to flip stones and shells in search of food.  This bird has a harlequin pattern of black, white and rust-red on the top of it.  It is a  black bibbed, white bellied, coral-red short legged bird.

Ruddy Turnstone

Sanderlings
  Although sanderlings can be found on almost every beach in the entire world, their population has decreased 80% in the past ten years. The way they find their food, including horseshoe crab eggs, is by running behind receding waves, poking around with its bill in search for small invertebrates, (animals with no backbone). A sanderling is 7 to 8.5 inches tall. It has bright rusty- red above and on the breast, with a white belly, and black legs that match with its black bill. The scientific name for this bird is Calidris alba.

Sanderlings

Semipalmated Sandpiper
The semipalmated sandpiper, or the Calidris pusilla, stands 5.5 in. tall to 7 in. tall.  It has gray on top and white below with a streaked breast.  It sleeps  with only one leg to stand on with its bill tucked into its back!  Like the sanderling, this bird runs along beaches above the wave line, capturing exposed aquatic insects for it to eat, as well as horseshoe crab eggs.