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 3. Species Information

3.1 Species Description

The Ivory Gull is a medium-sized gull, approximately 600 g with a wingspan of 94 cm, about 10% larger and longer-winged than the common Black-legged Kittiwake (Rissa tridactyla). It is distinctive at all ages, but is particularly striking in its pure white adult plumage, with black legs and an olive bill (Figure 1). Young Ivory Gulls are white with black speckling. Their nests contain 1 – 3 eggs, and can be a depression in the ground or a moss cup, and these can be located on isolated islands, flat, cobble limestone plateaus, or on steep cliffs of “nunataks” (mountain tops emerging from glaciers or ice caps; effectively an inland island surrounded by glacial ice) (Haney and MacDonald 1995). Nests are incubated by both parents for 24 to 26 days, eggs typically hatch in late July, and chicks fledge at 30 – 35 days after hatch. More complete descriptions of the species are found in Haney and Macdonald (1995) and COSEWIC (2006).

Figure 1 – Adult Ivory Gull © M. Mallory

Figure 1 is an image of an adult Ivory Gull photographed by M. Mallory.

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3.2 Population and Distribution

Ivory Gulls are distributed around the circumpolar region (Figure 2). Key breeding areas are the islands of northern Russia (Severnaya Zemlya, Franz Joseph Land), Norway (Svalbard), eastern Greenland, and the Canadian Arctic archipelago. A recent estimate of the global population is between 8,000 to 11,500 breeding pairs (Gilchrist et al. 2008), with declines noted in Svalbard and certain colonies in Russia, as well as Canada. Approximately 840 Ivory Gull individuals have been counted in Canada, or roughly 400 breeding pairs (Robertson et al. 2007). Wintering areas of Canadian birds are thought to be in the pack ice and marine waters between Greenland and Newfoundland/Labrador (Figure 2). A higher proportion of the global population winters in Canada than breeds here (an estimated 50-75%, or in some years perhaps as high as 100%), but the wintering population varies annually in response to sea ice distribution.

Figure 2. Known breeding colonies (black dots) of Ivory Gulls in the circumpolar Arctic. Stippled areas indicate the wintering range. Box around islands outlines approximate location of Figure 3.

Figure 2 is a map of the known breeding colonies of Ivory Gulls in the circumpolar Arctic. Two wintering areas between Greenland and Newfoundland and Labrador and between Greenland and Russia are also shown.

Figure 3. Known nesting colony locations of Ivory Gulls in Canada. Current colonies are those that are known to have been used at least once since 2002, while former nesting colonies are those which were last known to be used by Ivory Gulls before 2002.

Figure 3 is a map of the known nesting colony locations of Ivory Gulls in arctic Canada. Colonies where gulls have been observed since 2002 as well as former nesting colonies are shown.

Within Canada, Ivory Gulls are known to nest only in Nunavut at the following five locations: Ellesmere Island, Devon Island, Cornwallis Island, Seymour Island, and the Brodeur Peninsula of northern Baffin Island (Figure 3). As of 2009, almost all of the extant colonies were located on central, eastern Ellesmere Island (M. Mallory, unpubl. data.).  Helicopter surveys of all known breeding locations were conducted each year from 2002 – 2006, and then again in 2009 (Gilchrist and Mallory 2005, Robertson et al. 2007, Mallory unpubl. data).  Although additional breeding locations were discovered after 2002 (Robertson et al. 2007), of all 64 known breeding colonies in Nunavut, 25 (39%) have not supported any birds since 2002.  Ivory Gulls were once known to nest in the Northwest Territories in the Polynya Islands and on Prince Patrick Island (Cape Krabbe at the eastern margin of the Beaufort Sea) but have been abandoned since their initial discovery in the 1800s (MacDonald and Macpherson 1962).

In 2006, the known Canadian population size was approximately 842 individuals (Robertson et al. 2007), or roughly 400 breeding pairs. In the 1980s, Ivory Gull colonies were found in all of the areas identified in Figure 3, but by 2010, both the number of colonies and birds at extant colonies had decreased (Figure 4; COSEWIC 2006, Robertson et al. 2007), representing a >80% decline at colonies that were known in the 1980s. Including the new colonies found along east-central Ellesmere Island in 2006 (reconfirmed in 2009), the estimated population in 2009 (~ 800 birds) was 67% lower than the population estimated in the 1980s (~ 2400 birds; Thomas and MacDonald 1987).

Figure 4. Trends in numbers of Ivory Gulls counted on different island nesting areas in the Canadian Arctic, using maximum counts before 1990. Counts between 2002 and 2010 include new colonies found in the same general nesting area as the pre-1990 surveys. White squares show new colonies found on east-central Ellesmere Island, north of the old survey area, starting in 2004.

Figure 4 is a graph indicating the trends in the numbers of Ivory Gulls counted on different island nesting areas in the Canadian Arctic, using maximum counts before 1990. Counts between 2002 and 2010 include new colonies found in the same general nesting area as the pre-1990 surveys.

Colony size has declined markedly at the largest known colony on Seymour Island, at 2.7% per year (Robertson et al. 2007). Most colonies on the Brodeur Peninsula of Baffin Island have disappeared as have most colonies on eastern Devon Island and all colonies on southeast Ellesmere Island (south of Makinson Inlet) have declined or disappeared. The only region that supports apparently robust colonies of Ivory Gulls is the glaciated nunatak mountains of east-central Ellesmere Island.  Collectively, the “centre of gravity” of the Ivory Gull breeding distribution in Canada appears to have shifted north.

Local Ecological Knowledge

Local ecological knowledge (or Aboriginal Traditional Knowledge, ATK, or Inuit Qaujimajatuqangit, IQ) from Nunavut shows that Ivory Gulls are not concentrated near communities like they were in the past (Mallory et al. 2003). In fact, interviews with hunters and elders in Arctic Bay, Resolute Bay, and informally in Grise Fiord all suggested that the birds have generally been uncommon, but that local residents tend to see fewer now than in the past. It was the concerns of a local wildlife officer in Arctic Bay as well as hunters in Resolute Bay that first alerted the government to the decline of the Ivory Gull. In Newfoundland and Labrador, local ecological knowledge suggests that most birds are observed between September and May, typically as individuals or small groups (depending on wind and ice conditions), and that populations are at best stable, but possibly declining (Ryan et al. 2006).

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3.3 Needs of the Ivory Gull

In Canada, Ivory Gulls have simple but specialized habitat requirements. Specifically, they require breeding sites that are safe from terrestrial predators (particularly the Arctic Fox, Alopex lagopus), but in proximity (~ 50 km) of open water for feeding (closer than the 100 – 200 km stated in COSEWIC 2006, based on more recent data; M. Mallory, unpubl. data). The latter aspect potentially limits their breeding distribution, as the amount of ice-free ocean at the time that birds return to the High Arctic to breed is relatively small, except for certain polynyas (areas of open water surrounded by sea ice) and recurrent shore leads (COSEWIC 2006). Consequently, breeding sites tend to be remote islands, remote polar desert, or cliff faces of nunataks (COSEWIC 2006) near polynyas or a recurrent sea-ice / open water interface.  The remoteness of these sites may be important in protecting breeding Ivory Gulls from potentially adverse effects associated with human and other disturbances.  

Ivory Gulls are scavengers and predators, feeding at high trophic levels in the marine food web. They forage along the ice-water interface on fish and zooplankton, use multi-year ice as perches to sight feeding areas, follow polar bears to scavenge from marine mammal kills, and feed among the pack ice on seal afterbirth at whelping patches (Haney and MacDonald 1995). Sea-ice is extremely important to Ivory Gulls as a feeding and perching platform.

Species’ needs during the winter are largely unknown for Canada, in part because there is no tracking of Canadian birds to wintering sites (but see below). Birds winter in pack ice, near polynyas, or occasionally along marine shorelines (COSEWIC 2006). Orr and Parsons (1982) found many Ivory Gulls in Baffin Bay / Davis Strait, and recent satellite telemetry information suggests that this area is a main wintering site for Canadian birds as it is for birds from Greenland and Norway (H. Strøm, pers. comm.). Scientists believe that Ivory Gulls scavenge among pack ice and particularly near seal haul outs and whelping patches, where they scavenge for food in order to gather sufficient resources to migrate north again to breed.