Migratory Shorebirds

Overview: This quintessential “peep” (or small, brownish, easily confusable sandpiper) is endemic to the Americas—nesting on the tundra of northern Canada and wintering in the Caribbean and along the coast of northern South America. During their long migration journey spring and fall, “Semipalms” stop in New York City’s marshes in great numbers to rest and refuel. Most confusable with the Western Sandpiper, the Semipalmated Sandpiper is best differentiated from it by its straighter bill and less “hunched,” forward-weighted shape and posture.

 Where and When They Stop in NYC: Semipalmated Sandpipers migrate north through our area in May and June. And like other shorebirds that nest on the northern tundra, they return startlingly quickly: most pass through from July through October, hitting peak numbers in August. They may stop in any suitable habitat of marsh or mudflat, but congregate in the greatest numbers in and around Jamaica Bay, in the tidal wetlands of Staten Island, in the Bronx’s Pelham Bay Park, and in Manhattan’s Muscota Marsh.

 Conservation Status: The Semipalmated Sandpiper population consists of three North American breeding groups—western (Alaska), central (western Canadian Arctic), and eastern (eastern Canadian Arctic). Our eastern population appears to be in decline, and is on the 2014 State of the Birds watchlist.
 
 

Overview: The Red Knot is a large, colorful sandpiper with a global range—breeding on the northern tundra to within the Arctic Circle and wintering on coasts across the world as far south as Tierra del Fuego, the Cape of Good Hope, and New Zealand. Its migration is among the longest of any animal, as much as 9,300 miles in both spring and fall, including non-stop flights of 1,500 miles or more. 

 

The Rufa subspecies (Calidris canuta rufa), which passes through our area, has evolved to time its spring migration with the spawning of the Atlantic Horseshoe Crab, and depends on this ancient animal’s energy-rich eggs to fuel its long migration flights. Read more about horseshoe crabs and NYC Audubon’s horseshoe crab monitoring program.
 

Where and When They Stop in NYC: Red Knots migrate north through our area in late May and early June, and return in August and early September; some birds may linger through the winter when weather is mild. They are most often seen in marsh and mudflat habitat in and around Jamaica Bay and on the southern shore of Staten Island.

 Conservation Status: 

The three subspecies of Red Knot found in North American are in decline; our Rufa subspecies is listed as Threatened, both federally and in New York State. Read more about the conservation status of the Red Knot on the U.S. Fish and Wildlife Service website.

Overview: The Sanderling is well named—it is the beach bird across most of our planet, beloved for chasing the surf as it ebbs and flows, its small dark legs a blur of motion. Beaches and (to a lesser extent) mudflats and marshes are the species’ habitat most of the year, but it breeds on the High Arctic tundra. Outside breeding season, this small sandpiper is identified by its pale gray and white coloring, black legs and bill, and the black-and-white marks on its shoulder. From May to August, you may get to see the rusty orange head and breast of the male’s breeding plumage. (Unlike most of our sandpipers, the Sanderling is sexually dimorphic; in breeding plumage, the female’s upperparts are a more subdued beige-brown.)

 

Where and When They Stop in NYC: Like the Red Knot, the Sanderling depends upon horseshoe crab eggs for substance as it migrates north in spring, and so migrates through our area at the same time, in late May and early June. Peak numbers are seen in the City during the southward migration, from late July through August—but a good number of Sanderlings spend the winter here as well. These beach-runners are most often seen on beaches in and around Jamaica Bay and on the southern shore of Staten Island.

 Conservation Status: Sanderling surveys in various parts of the U.S. have shown concerning population declines of up to 80 percent; however, exact Sanderling population sizes and the causes of these declines are not well understood. The species is considered “abundant” in New York according to the New York State Department of Environmental Conservation, but the Western Hemisphere Shorebird Reserve Network (PDF) deems the Sanderling a “Species of High Concern” across North America “because of its significant population declines, widespread habitat loss, and the threats it faces during the nonbreeding seasons (migration and winter).”

Many other migratory shorebird species stop through New York City during migration, including Least Sandpiper, Greater and Lesser Yellowlegs, Short- and Long-billed Dowitchers, Dunlin, Black-bellied Plover, Ruddy Turnstone, and others. To see which other shorebird species stop here and when, see Bird bar charts for New York City, for the years 2000-2020.

Atlantic Horseshoe Crab (Limulus polyphemus) is an ancient species; it has remained relatively unchanged for four million years, making it older than the dinosaurs (and therefore older than birds!). Despite its English name, the horseshoe crab is not a crab at all—it is more closely related to spiders and scorpions. (And despite its Latin species name, that of the mythical cyclops Polyphemus, the horseshoe crab has a total of ten eyes spread about its body!)

 

During the breeding season, Atlantic Horseshoe Crabs migrate to shallow coastal waters. They arrive in the thousands--and sometimes hundreds of thousands--on the beaches of the Atlantic Coast during the new and full moon in May and June. The typically smaller male selects a female and clings to her back using a claw specialized for this purpose, while other “auxiliary” males surround her as well. The female digs a hole in the sand and lays her eggs while the males fertilize them. The female can lay between 60,000 and 120,000 eggs in batches of a few thousand at a time. These eggs are a critical food supply for migrating shorebirds like the Red Knot.

 

A horseshoe crab grows by molting. As it matures and increases in size, it sheds its old exoskeleton (outer shell or skeleton) up to 17 times and forms a new, bigger one. At around 10 years of age, horseshoe crabs reach adulthood and no longer molt. They are ready to start breeding and will migrate to coastal beaches in the spring. A horseshoe crab can live for more than 20 years. 

 

Threats to horseshoe crabs include habitat loss and overharvesting for use as bait in eel and whelk fishing. Thousands of horseshoe crabs also die every year when live crabs are “bled” for the biomedical industry: The crabs’ light blue blood contains a substance that creates a visible reaction in the presence of pathogens, and is thus widely used in safety testing of medical substances used in the human body¹. A synthetic alternative is available², which if adopted may reduce the exploitation of horseshoe crabs for this purpose. (Read more in this thorough article in The Atlantic.). Learn more about horseshoe crabs and their conservation on the Horseshoe Crab Recovery Coalition.