The Birds of Ocracoke The Gull-billed Tern

Text and photos by Peter Vankevich

The terns of Ocracoke Island can reliably be seen flying along its coastal waters and loafing on the beach. One of these species, whose family is related to gulls, is a bit of an outlier. 

The Gull-billed Tern can also be found in a variety of salt and freshwater habitats such as salt marsh ponds, lagoons, canals, flooded fields and even bushy thickets, which explains why it was once known as the Marsh Tern. Their diet reflects their environment.

“While other protected tern species, such as Least and Common Terns, feed on aquatic prey through plunge-diving in the surf zone, Gull-billed Terns mainly feed on terrestrial prey, such as insects and ghost crabs,” said Amy Thompson, Ocracoke’s lead biotechnician for the Cape Hatteras National Seashore. “We often see them flying along the backshore, then stop to hover over ghost crab burrows in an attempt to snatch one up.”

These terns can also be seen alongside South Point Road, hawking large insects like dragonflies and cicadas.

The Gull-billed Tern is a medium-sized tern best identified by a large, all-black bill, described as gull-like, hence its name. It also has black legs.

In breeding plumage, like most terns, it has a black cap and a pale gray mantle and white underparts. In its basic, or nonbreeding plumage, the black cap is missing and has just a smudge behind the eye. It is approximately 14 inches in length with a 23-inch wingspan.

On Ocracoke, it can be confused with the Sandwich Tern, which has a shaggy black crest, and its black bill is thinner with a bright yellow tip.

Gull-billed Terns can be found world-wide in parts of Europe, Asia, Africa, Australia and the Americas.

In North America, they breed along the Atlantic Coast, from Long Island south to Florida and along the Gulf Coast to Texas and southernmost California down the coast of western Mexico.

They arrive on the Outer Banks for nesting in April and by the end of August most will have departed for their wintering range primarily southwest Florida, the Gulf Coast, Mexico and the Caribbean.

Gull-billed Terns (Gelochelidon nilotica, formerly Sterna nilotica) are listed as a species of “Least Concern” by the International Union for Conservation of Nature (IUCN).

While the “Least Concern” status may be due to their worldwide distribution, the Carolina Bird Club has sounded an alarm regarding its steep decline along the Atlantic coast over the last decade.

Thompson echoes the bird club’s concerns.

“Over the past few years, we have not documented any Gull-billed Tern fledging success on Bodie, Hatteras or Ocracoke Islands,” she wrote in an email. “Since 2020, there have been 26 nests confirmed (all on South Point), which includes the one nest so far this year; but no fledglings have been observed.” This year there is one chick in the colony that it is hoped will successfully fledge.

As with the other colonial nesting species, Common and Least Terns and Black Skimmers, gull-bills nesting failures in recent years on Ocracoke can be attributed to increased animal predation and overwash from major spring storms that destroy their nests.

Breeding does not occur until five years of age. Their nests on the sand are not much more than a slight depression lined with a few bits of shell and vegetation like dune grass.

They lay two to three eggs, which are incubated by both parents for about three weeks. The hatchlings leave the nest area within a few days and take cover in beach vegetation where they continue to be fed by their parents until fully fledged, which takes about 25 days. Chicks beg for food by pecking at the parent’s bill.

Best time to see: April into late August.

Where: Along the beach and in the Pamlico Sound. The sides of the road to South Point (Ramp 72) are a good location to see them hawking large insects.

Listen: 

https://macaulaylibrary.org/asset/29742721

(Audio provided courtesy of the Cornell Laboratory of Ornithology Macaulay Library

Some bird species, like the Lesser Black-backed Gull in Europe and in the United States, the American Oystercatcher and several species of terns, facing loss of natural habitat, have started nesting on gravel-covered roof tops. Gull-billed Terns were discovered nesting on a roof top of a Wall Mart in Northwest Florida.

Gravel rooftops can resemble beach habitat: they are flat, open, and have loose gravel in which to build a nest and lay their eggs.  They have become attractive to birds because they are largely free of human disturbance and many of the predators lurking on the beaches.

Audubon Florida has developed plans and provide assistance on how roofs can be modified to increase breeding success.

The Birds of the Outer Banks checklist, produced by the U.S. Fish and Wildlife Service, has been recently revised by Ricky Davis of the Carolina Bird Club.

A total 16 species of gulls and 14 terns are listed, but eight of them are among the “Very Rare/Accidental Species” on the back page.

This informative checklist is available free at Ocracoke’s NPS Discovery Center and at the Pea Island National Refuge Visitors’ Center.