Wildlife & Habitat

Common terns resting on South Monomoy Island's shore. Sarah E. Devlin 2019 - 492x210

Binoculars are available to lend at the Visitor Center! Feel free to borrow a pair to help you get a good look at our wildlife.

In 1999, the refuge was designated part of the Western Hemisphere Shorebird Reserve Network. The migration route starts in the Arctic and eastern Canada and continues south along an “outer coast” flyway which includes the entire outer Cape. Monomoy, a largely undisturbed coastal habitat, acts as an important stopover point, breeding ground, and overwintering site for many species of songbirds, shorebirds, and seabirds. 

The saltmarsh and sandflat habitat of North Monomoy attracts gulls and shorebirds including egrets, glossy ibis, godwits, dowitchers, yellowlegs, and many species of sandpipers. South Monomoy Island is home to the largest colony of common terns in New England at over 13,000 nesting pairs, as well as least terns, roseate terns, American oystercatchers, piping plovers, black-bellied plovers, and occasional vagrant snowy owls in winter. The wide sandflats and mudflats skirting the island provide rich beds of shellfish and marine invertebrates that are vital foraging habitat for thousands of shorebirds, and the island’s freshwater wetlands and ponds are ideal sheltering and feeding habitat for dabbling and diving ducks.

Here, we highlight the iconic and significant species and habitats of the refuge.
Check out the Monomoy Bird Brochure (pdf) for a full bird list.

  • Piping Plover

    Piping plover - Amanda Adams/ USFWS 2019

    The federally threatened piping plover (Charadrius melodus) is a small sand-colored shorebird that nests and feeds along sandy beaches throughout Cape Cod. During the breeding season, upwards of 50 pairs of piping plovers can be found nesting on South Monomoy Island. They can be identified by their short, stout bill, yellow-orange legs, black band across the forehead, and a black ring around the neck. Their name derives from their call, which sounds like a series of bell-like whistles.

  • American Oystercatcher

    American oystercatcher - USFWS.

    The American oystercatcher (Haematopus palliatus) is a species of concern in Massachusetts. It is a large shorebird living in coastal salt marshes and sandy beaches, specializing in eating bivalve mollusks. The oystercatcher has a dark head, back, and wings, with a white underbelly and long reddish beak. Its legs are long and a pale-pink color, and its eyes are yellow with a red ring around them. Their breeding range is along the Atlantic coast from Boston, MA south to Florida, and they occasionally wander north to Maine.

  • Roseate Tern

    Roseate tern - Amanda Boyd/USFWS.

    The roseate tern (Sterna dougalli) is a pale, medium-sized tern that is protected under the Endangered Species Act. Northeastern individuals almost always breed in colonies with Common or Arctic terns. This tern can be identified by the black “cap” on its head, its dark red beak, grey back and white forked tail. They can be seen plunge-diving to feed on small schooling marine fish, often submerging completely when they dive. During the breeding season, roseates can be found nesting in the tern colony on South Monomoy Island.

  • Red Knot

    Red Knot - Yianni Laskaris / USFWS

    The red knot (Calidris canutus), a federally threatened species, is a bulky shorebird with a stout, black bill, reddish belly and mottled gray back. This bird undertakes one of the longest migrations known, traveling from its furthest wintering ground at the tip of South America to its Arctic breeding grounds and back again each year; an estimated 16,000-mile round trip! Protection of breeding, migration, and wintering habitat is critical to this species’ recovery. Southeastern Massachusetts, and Monomoy NWR in particular, are likely to provide some of the most important sites for adult and juvenile red knots during their southward migration from July through October.

    Refuge staff and partners capture and tag red knots each fall. Collecting this data allows researchers to assess habitat condition, work toward minimizing disturbance, and better understand the health of the population.

  • Seals

    Harbor seal - Sarah E. Devlin

    Monomoy is home to growing populations of gray and harbor seals. Between 30,000-50,000 seals use the lands and waters around the refuge. Seals haul-out on shore to rest, give birth, and feed their pups, returning to the water to feed on fish, crustaceans, and shellfish. On land, their movement is slow and awkward, but in water they can swim quickly to catch prey and avoid predators -- including the great white shark, a frequent summer visitor to refuge waters.

    After years of being hunted for bounty by those believing they depleted fish stocks, seals were largely extirpated (i.e., locally extinct) from Cape Cod and were given protection under the Marine Mammal Protection Act of 1972. This act made it illegal to kill or otherwise harass seals. As a result, the population has rebounded, which has likely led to a steady increase in white shark populations around Cape Cod. A conservation success story, the rebounding seal and shark populations of Cape Cod are a testament to how regulatory protections can allow ecosystems to recover after decades of over-exploitation.

    Monomoy NWR actively supports seal research each year to better understand seal ecology, population structure, movement rates, and diet.

    Gray Seals

    Gray seals established a small rookery, or breeding colony, on South Monomoy in 1990, and are now seen there year-round. Monomoy NWR is now the largest haul-out site for gray seals in the entire United States! The Cape and Islands mark the southern end of their breeding range. Gray seals are easily differentiated from other seals by their long “Roman” noses, often referred to as “horse heads.” While haul-outs occur in large aggregations along beaches, they are solitary hunters in the water. Seals are very curious, and will often swim alongside boats or shorelines to watch people.

    Harbor Seals

    Harbor seals can be found on Monomoy between August and May, spending the rest of the year in Northern New England and Canada. They are significantly smaller than gray seals, with much shorter noses and larger eyes. Their distinctive eyes contribute a “puppy-like” quality to their faces. When hauled out on land, these seals become agitated when humans come close, but once in water they can be curious and swim near boats. During haul outs, they can mix with groups of grey seals.


  • Whales and Dolphins

    Whale tail - USFWS

    Whales and dolphins that can sometimes be sighted around Monomoy include the humpback whale, critically endangered North Atlantic right whale, finback whale, long-finned pilot whale, Atlantic white-sided dolphin, common dolphin, harbor porpoise, and others. The fall months are a great time to catch a glimpse of southward-migrating whales from our Morris Island headquarters overlooks (ask for binoculars!)

  • Northeastern Beach Tiger Beetle

    Northeastern beach tiger beetle - USFWS

    The federally threatened northeastern beach tiger beetle requires undisturbed sandy habitats free of heavy foot and vehicle traffic, such as those found on Monomoy. These insects live along the Atlantic coastline from Cape Cod to New Jersey, as well as along the Chesapeake Bay. In the summer they live in the intertidal zone of beaches and migrate closer to the dune line in the fall. Their population declined due to increases in off road vehicles (ORV), pedestrian beach traffic, and shoreline changes (i.e., coastal development and beach stabilization structures). Because of this, The Monomoy Wilderness offers ideal habitat conditions. Today, only 3 populations exist north of the Chesapeake Bay.

    Reintroduction to South Monomoy Island:

    The reintroduction project began when 23 larvae from Martha’s Vineyard were transplanted to South Monomoy in May of 2000. A second transplant released 34 more larvae. This trend was continued annually until 2004. The project has been highly successful, with a current population well in excess of 8,000 individuals. As northeastern beach tiger beetles are indicators of a healthy beach community, their success is highly significant for Monomoy NWR’s ecosystem.

  • Horseshoe Crabs

    Horseshoe crab - USFWS

    Every spring and early summer, adult horseshoe crabs gather in shallow waters, migrating to shore during high tides. Spawning adults are particularly numerous during the full or new moons. Females dig 6-8 inches into the sand, laying golf-ball sized clutches of eggs. Each female can lay over 88,000 eggs

    Monomoy is the most significant breeding site for horseshoe crabs on Cape Cod. Their presence is a positive indicator of marine ecosystem health, and their eggs are a vital source of food for shorebirds that rely on the refuge to rest and breed.

    The U.S. Fish & Wildlife Service collaborates with the National Parks Service and Massachusetts Audubon Society in a study of horseshoe crab populations on Cape Cod. This study continues today and is conducted on the refuge as well as other sites throughout Cape Cod. Re-sightings of tagged crabs are recorded and communicated to a special hotline 1-888-LIMULUS (546-8587)that was established to allow the public to report sightings. We encourage visitors to look for tags and report them if found! This data is used to track population dynamics and migration patterns. Due to their importance to the local ecosystem, harvest of horseshoe crabs is prohibited by law.

  • Seabeach Amaranth

    Seabeach amaranth - Devan Blazey / USFWS

    In 2017, Refuge staff and partners out-planted 2,000 seeds of the federally threatened seabeach amaranth plant on the beaches of South Monomoy Island. An annual member of the amaranth family, seabeach amaranth has reddish stems and small, rounded, notched, spinach-green leaves. Seabeach amaranth is native (endemic) to Atlantic Coast beaches and barrier islands, historically occurring from North Carolina to Massachusetts.

    Threats to seabeach amaranth include beach stabilization (particularly the use of beach armoring, such as sea walls and riprap), intensive recreational use, mechanical beach raking, and herbivory by insects. Monomoy, with its wide swaths of remote, wilderness beach, provides near-ideal habitat for this species.

  • Dune and Beach Ecosystem

    Dunes - Zachary Cava/USFWS.

    A significant component of coastal habitat protection and resilience entails preserving natural dune systems. American beach grass, dusty miller, and beach pea are just some of the plants that anchor and stabilize our waterfront dunes. If dunes are destroyed or breached, whatever lies behind them, including wetlands and shorefront homes, is vulnerable to the water and wind. The dunes also provide habitat for nesting birds and other animals.

    Although dune plants tolerate harsh beach conditions (wind, salt spray, over wash of waves), they can’t withstand the pounding of feet and vehicles. Therefore, strict rules are in place to remain on walking paths to protect the dune system and the other ecosystems in the area.

  • Salt Marsh

    Salt marsh - USFWS

    Monomoy NWR contains over 700 acres of rare pristine and unaltered saltmarsh. Salt marshes are coastal wetlands that are flooded and drained by salt water brought in by the tides. They are marshy because the soil may be composed of deep mud and peat, made of decomposing plant matter that is often several feet thick. Salt marshes protect shorelines from storms and erosion by buffering wave action and trapping sediments. They reduce flooding by slowing and absorbing rainwater, and protect water quality by filtering runoff.

    A fresh supply of nutrients is washed into the salt marsh twice daily, supporting many different types of plants, crustaceans, fish, shorebirds and waterfowl. Shorebirds and waterfowl are attracted to the abundance of food these marshes provide, and many species of fish, including the striped bass, feed in the saltmarsh, and use it as a nursery to raise their young. 

    Just like coral reefs, salt marshes are vital resting, sheltering, and breeding grounds for wildlife that link together many different, complex processes in the web of life.

  • Freshwater Ponds

    Big Station Pond - Amanda Adams / USFWS

    The freshwater ponds and marshes, which cover more than 150 acres on South Monomoy Island, host cattail, pond lilies, and common reed. Big and Little Station Ponds are 32-acre and 11-acre freshwater ponds, respectively, on South Monomoy Island, originally formed when a bay was closed off by the growth of a re-curved spit. Most freshwater ponds are natural, but a few lie in depressions excavated by the Service in the early 1950s in an effort to increase waterfowl habitat. 

    South Monomoy’s freshwater ponds and marshes provide important breeding, migratory stopover, and wintering habitat for waterfowl. Redhead, bufflehead, common goldeneye, hooded merganser, lesser scaup, greater scaup, ring-necked duck, canvasback, pied-billed grebe, American coot and others have all been found to use Monomoy’s freshwater ponds as migratory stopovers. American black duck, mallard, gadwall, green-winged teal, Virginia rail, sora, and numerous other species of waterfowl, many of which are rare breeders in eastern Massachusetts, depend on South Monomoy for breeding habitat.