Ross's Gull Life History

Habitat

Ross’s Gulls breed in marshy tundra habitats around ponds or in river deltas, where there are sometimes scattered dwarf shrubs, especially willows and alders. They often nest in small colonies (around 10 pairs), sometimes near Arctic Terns. After the breeding season, they forage near pack ice in the Arctic Ocean. At Utqiagvik (formerly Barrow), Alaska, large numbers—sometimes thousands—pass eastward in autumn to feed in the Beaufort Sea. Several weeks later, they return and then fly to destinations unknown. Several satellite-tracking studies showed westerly movements after breeding, with birds predominantly moving through the seas that ring the southern edge of the Arctic Ocean: the Beaufort, Chukchi, East Siberian, Laptev, Kara, Barents, Greenland, Norwegian, and Labrador Seas. Vagrants in the continental U.S. usually turn up among other small gulls, especially Bonaparte’s Gulls, along rivers, coastlines, at wastewater treatment facilities, or warm-water discharges from power plants. Back to top

Food

Ross’s Gulls feed on invertebrates and marine vertebrates, especially small fish. Nesting birds eat mostly insects such as midges and caddisflies, which they devour rapidly, like a shorebird or pipit. They forage in ponds like a phalarope, stamping their feet and spinning to stir up and concentrate prey. On mudflats, they race like plovers to pick up prey. During the rest of their life cycle at sea, they eat mostly small crustaceans, mollusks, marine worms, and fish. Ross’s Gulls forage singly or in small flocks when at sea. They take prey on the wing by dipping down and picking items from the water’s surface or just beneath it, or while swimming. They often orient into the wind, close the wings partly, and “walk” along the water to access prey more precisely (or perhaps to agitate prey), recalling a foraging storm-petrel. In flight, Ross’s Gulls are remarkably agile, equipped with a fine bill and narrow, pointed wings, which permit them to select small prey items quickly and precisely and maneuver capably in extreme conditions. Like other arctic species, Ross’s Gulls eat prey that lives under the ice, so they sometimes follow ships to seize prey dislodged by the ship’s pressure wave. Like small sandpipers, they eat “biofilm,” a mixture of plankton, microbes, and detritus that washes up on beaches and in other intertidal areas. There are reports of Ross’s Gulls picking at walrus dung as well as carrion, much as Ivory Gulls do, and on occasion they forage at sewage outfall pipes. Back to top

Nesting

Nest Placement

Nests are set on small rises (hummocks or tussocks) in marshy tundra; areas that are drier than surroundings.

Nest Description

Male and female construct a cup of grasses, sedges, and reindeer moss.

Nesting Facts

Behavior

When they arrive on nesting grounds in late May or June, Ross’s Gulls begin courtship immediately. Males fly around a territory and call loudly, an insistent yi-ki, yi-ki, yi-ki sounding a bit like a shorebird. If a female is present, the male may land, lower the breast, raise both head and tail, and call, his body contorted into a U shape. The female may respond in kind, and the two walk in circles together. Both sexes build the nest, incubate eggs, and feed young. Males defend their mates, territories, and nest sites, but even in colonies (rarely more than 10 pairs), the nests are spaced out sufficiently that conflicts are rare. Nests tend to be well hidden, and the adults cautiously come and go from the nest site, so much so that entire colonies are easy to overlook. When predators come near the nest or chicks, adults attempt to draw the predators away by feigning injury—or even by pretending to feed a chick that is not there. These tactics are more typical of shorebirds, especially plovers, but also Sabine’s Gull. After the chick’s first week, adults may gather chicks from several nests into one area.

Conservation

The remote breeding and wintering areas of Ross's Gull make assessment of population trends difficult. Partners in Flight estimates a global breeding population of 42,000 and rates the species a 15 out of 20 on the Continental Concern Score. They include it on the Yellow Watch List for species with restricted ranges. Other estimates suggest as few as 10,000 breeding pairs may exist. As recently as 2011, a five-week count of migrants at Point Barrow, Alaska, tallied more than 27,000 (note that total numbers of a species are always larger than numbers of breeding individuals). The chief conservation concern for Ross's Gulls is the impact of climate change on its habitats and food resources. Additional threats include predators such as foxes, jaegers, larger gulls, and raptors. Petroleum development in nesting areas and in arctic seas could also have negative impacts.

Credits

Alvo, R., D. McRae, S. Holohan, and G. Divoky. (1996). Updated status report on the Ross’s Gull Rhodostethia rosea in Canada. Committee on the Status of Endangered Wildlife in Canada. Environment Canada, Ottawa.

Kushlan, J. A., M. J. Steinkamp, K. C. Parsons, J. Capp, M. A. Cruz, M. Coulter, I. Davidson, L. Dickson, N. Edelson, R. Elliott, R. M. Erwin, S. Hatch, S. Kress, R. Milko, S. Miller, K. Mills, R. Paul, R. Phillips, J. E. Saliva, W. Sydeman, J. Trapp, J. Wheeler and K. Wohl (2002). Waterbird conservation for the Americas: The North American waterbird conservation plan, version 1. Washington, DC, USA.

Partners in Flight. (2020). Avian Conservation Assessment Database, version 2020.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

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