Sabine’s Gull

Xema sabini is a small gull of the family Laridae, accepted in the World Register of Marine Species under the genus Xema ^[1]. It breeds thinly scattered across the Arctic and spends the northern winter in the southern hemisphere, where the large majority of tracks from the Canadian Arctic ended up off the coast of Peru ^[2].

It spends most of the year over open water far from land, so in Peru it is an open-sea visitor that reaches its wintering area around November ^[2].

The species has a fragmented breeding range around the Arctic and, over much of that range, prefers low tundra associated with freshwater or tidal marshes ^[2]. At the studied site on Nasaruvaalik Island, Nunavut (75.8° N), it nests on low gravel ridges with moss, saxifrage and shallow ponds ^[2].

Outside the breeding season it is highly pelagic, and every breeding population is presumed to reach one of two large upwelling zones of the southern hemisphere: the Humboldt Current off Peru, in the Pacific, or the Benguela Current off South Africa and Namibia, in the Atlantic ^[2]. Of 28 geolocator tracks that reached a wintering site, 26 went to the Pacific and 2 to the Atlantic ^[2].

47 geolocators were deployed on 33 breeding adults on Nasaruvaalik Island, and 38 of them were recovered ^[2]. The birds left the colony at the end of the Arctic summer: the mean was 18 August for those heading to the Pacific, with a range from 5 August to 3 September ^[2].

The autumn journey took 84 days on average and covered about 14,578 km to the Pacific, at about 347 km per day on travel days; arrival at the wintering area came around 11 November, between 15 October and 6 December ^[2].

The 10 birds followed for 2 years returned to the same wintering site in both years ^[2]. A pair confirmed over 6 seasons, from 2009 to 2014, wintered in different oceans in the 2 consecutive years it was tracked, the female in the Pacific and the male in the Atlantic ^[2].

On Nasaruvaalik Island it nests alongside the Arctic tern Sterna paradisaea and Ross's gull Rhodostethia rosea, in 2 colonies, with 16 to 31 pairs per year over 8 years ^[2]. The island has nearby polynyas that offer reliable food when the surrounding sea is still frozen early in the breeding season ^[2].

It forms pair bonds that last several seasons, and breeding success on this High Arctic island was higher than that of birds in more typical Low Arctic settings ^[2]. In winter its behaviour depends more on prey availability, genetics and climate than on coordination within the pair ^[2].

The global IUCN category is Least Concern (LC) ^[3]. Little is known about birds breeding in the northernmost part of the range, and Nasaruvaalik Island, with 16 to 31 pairs per year, is regarded as one of the most important sites for ground-nesting seabirds in the Canadian High Arctic ^[2].

The authors of the tracking studies make no specific conservation recommendations, and this account has no sources on threats in the Peruvian wintering area ^[2].

Birds tracked from the Canadian Arctic in 2008 to 2012 wintered in the Humboldt Current off Peru, arriving on about 11 November on average ^[2]. In the Alaskan Arctic 12 geolocators were deployed in 2011 (4 recovered) and 5 GPS tags in 2021, and overall the birds migrated to the Humboldt Current off Peru ^[4].

It is an open-sea bird in winter ^[2]. The sources consulted give no shore-based watching sites or access conditions, so this account gives none ^[2].