Red Knot (Calidris canutus)

After journeying from the southern tip of South America, the red knots that appear on the shores of Delaware Bay in May arrive so thin that they look like sparrows.There they gorge themselves on the eggs of the horseshoe crab (Limulus polyphemus), putting on a layer of fat so thick that they leave for their Arctic breeding grounds looking like plump doves.At least five other shorebird species use the bay as a spring migratory stopover.Among them, however, the red knot is the largest and stockiest.In its May-August breeding plumage, it also sports a distinctive breast of brilliant rusty red.Also described as pale salmon, this russet color extends up the neck and around the eyes, and bleeds somewhat into the patterned black, brown, gray and white colorations on the wings and back.The rump is whitish.The knot has a short, straight black bill and, during breeding season, dark brown/black legs.A small number of the adults arrive in the middle of their molt showing various amounts of the non-breeding plumage that is typical between September and April: a washed-out gray look with scaly white feather edgings, whitish flanks with dark barring and greenish legs.Juveniles are primarily gray, with a scaly pattern on the wings and dull yellow-olive legs.Passing through New Jersey again in August, adult red knots remain in breeding plumage and with many other species.During both the May and August migrations, whimbrels or Hudsonian curlews (Numenius phaeopus) look most similar to knots, but their breasts are duller, contrasting less with the rest of their bodies.Also, whimbrels are larger and their decurved bills are twice as long.As with most shorebirds, the long-winged, strong-flying knots fly in groups, sometimes with other species.