Sabine’s Gull––A distinctive and unusual tern-like gull
On a recent evening drive along Safety Sound, I was excited to spot four small, black-headed Sabine’s gulls flitting daintily up and down in the wind and waves along the Norton Sound beach. These striking gulls regularly visit our shores during spring migration, but I hadn’t seen them here in fall before.
At first, through dimming light and rain-splattered windows, I thought three young Arctic terns were with them. But no, they were juvenile Sabine’s gulls––very interesting to me, since I’d never seen juveniles in the area before.
The Sabine’s gull is the only species in its genus. This interesting and unique gull differs from other gulls in many feeding habits and breeding behaviors, which are more tern- or shorebird-like than gull-like.
The small and distinctively marked Sabine’s gull breeds around the circumpolar north. A long-distance migrant, this is the only arctic-breeding gull known to fly south of the equator, where they winter in upwelling areas of the open ocean.
In spring, flocks of Sabine’s gulls usually reach Seward Peninsula waters during the second half of May. Migrants, mostly in route to breeding grounds further north, can be seen feeding with other seabirds along Norton and Safety Sound shorelines where aquatic invertebrates wash into the shallows.
Sabine’s gulls nest in wet meadow habitats. Nests are placed on islands or peninsulas of tundra ponds, or on hummocks or tussocks in the wetlands. They also nest in salt grass meadows, and seldom far from the coast, tidal sloughs or estuaries.
In Birds of the Seward Peninsula, Brina Kessel reported the highest nesting densities in the wet meadows along the peninsula’s northern coast. Elsewhere on the peninsula’s perimeter, nesting was documented mostly near river mouths. I am not aware of Sabine’s gulls nesting in the Nome area.
Sabine’s gulls, like many seabirds, tend to form long-term, monogamous pair bonds, often reuniting on the same territory year after year. Studies have found that when pairs are familiar with each other and their territory, they tend to have higher breeding success than do newly formed pairs.
Interestingly, a pair of tagged Sabine’s gulls that nested in the Canadian Arctic reunited on their breeding territory for multiple years, after wintering on opposite sides of the globe––one in Pacific waters off the coast of Peru, and the other in the Atlantic, west of South Africa and Namibia.
When courting and bonding, the male presents his mate with prey, one item at a time, carried in his bill. Terns court in this way, whereas other gull species regurgitate a slurry of prey to charm their mate.
Sabine’s gulls usually nest in small, loose colonies. Both birds work to create a shallow depression on the ground that they may line with bits of grass, or with nothing at all. The female lays an average of two eggs that both birds incubate for about 22 days.
Newly hatched chicks are covered in cryptically colored down and leave the nest within about 24 hours to hide in the surrounding vegetation. Such quick departure from the nest is typical of terns—but not of most other gull species, whose chicks spend weeks in their nest.
Both parents feed and defend their chicks. When a predator threatens the nest or young, the parents may perform a distraction display to lure the threat away. This is a common defensive behavior for shorebirds, but rare for gulls. Or, defensive parents may mount agile, aerial attacks aided by other members of the colony, sometimes striking the predator with feet, bill or excrement.
The young are able to fly short distances in about 20 days, before their flight feathers are fully grown in. This too is typical of terns, rather than gulls.
On the breeding grounds, adults and their young feed mainly on larval and adult insects, aquatic invertebrates and spiders, using a variety of search-and-capture techniques.
While walking or swimming through the wetlands, the gulls pick prey from the vegetation and water—like shorebirds do. They wade in shallow water searching for food on the bottom, sometimes stirring the sediment with their feet to flush prey. Or they may sit on the water and spin, drawing prey to the surface as phalaropes do.
Sometimes these small, agile gulls snatch flying insects in flight, and occasionally they eat the eggs or nestlings of other birds or steal fish from nesting Arctic terns.
When the young fledge, the parents and juveniles leave the breeding grounds and fly to the coast to feed in preparation for their long migration. There they run along the shoreline and feed in mudflats like plovers; flip stones and debris like turnstones; pick tiny organisms out of the water while swimming, spinning or surface plunging like phalaropes; or swoop nimbly over the water to grab small fish or crustaceans, like terns. They also scavenge the beaches for small, marine organisms that wash up.
Typically, most Sabine’s gulls leave their breeding areas in early August, but if nesting is delayed by spring conditions, departure may be later. The main southward migration from the Seward Peninsula is usually in September, with adults leaving first. Migration is often in tight flocks, at night.
Alaska’s Sabine’s gulls winter in upwelling areas off the Pacific coast of South America.
The population trend for the Sabine’s gull is unknown. Climate change, which is altering the ocean and tundra ecosystems where these gulls winter and breed, is the main concern for this species, but the effects are as yet unknown.
This year, for the first time in the Nome area, there were regular eBird reports of Sabine’s gull sightings over the summer and fall. This, and the presence of juveniles this fall, raise the exciting possibility that these pretty gulls may have established a new colony nearby.
Time will tell.