Ivory Gull
Pagophila eburnea
Description 3
This distinctive gull is most striking in appearance when in its pure white adult plumage (3), which blends beautifully into its icy, Arctic habitat. Immature ivory gulls also have white plumage, but have a scattering of brownish-black spots on the body and the tips of the wing feathers (2). In the young gull's second winter, this is replaced with the brilliant white plumage (3). The ivory gull has dark eyes and a bill that is slate blue at the base, turning pale yellow and tipped with red. It has short, black legs, which with its stocky-build and rolling gait gives it a pigeon-like appearance on the ground. Despite its appearance when walking, the ivory gull is an agile and graceful bird when in the air (3).
Biology 4
The ivory gull breeds from late June to August, forming colonies consisting of 5 to 60 pairs. Nests of moss, straw and debris are built, situated on bare, snow-free rock and lined with dry grass and feathers. Generally two eggs are laid and incubated for 24 to 26 days. The chicks fledge after four to five weeks (2). Following breeding, ivory gulls immediately leave their colonies and disperse to their winter habitat to forage (3). Like many other gulls, this Arctic species is an opportunistic feeder (3), consuming a wide range of foods that it encounters. Small fish, such as lantern fish and juvenile arctic cod, and large zooplankton are plucked from the sea's surface, and they may also catch small mammals (3). They scavenge on dead fish and the carcasses of mammals, and will often follow polar bears and human hunters to feed on the scraps from their kills. The excrement of polar bears and seals is consumed, as well as the placentas of seals, and in the extreme cold of winter it is even known to swallow large pieces of frozen food (2). The ivory gull is vulnerable to a number of predators; polar bears and a number of birds prey on both eggs and young ivory gulls, and the best-known predator, the artic fox, is known to be capable of destroying entire breeding colonies situated on flat ground (3).
Threats 5
In parts of its range, ivory gull numbers have fallen rapidly (4). For example, surveys of breeding colonies in Canada in 2002 and 2003 revealed that populations had declined by 80 percent since the early 1980s (5). These declines are believed to be the result of a number of factors (4). During the breeding season, the ivory gull is very vulnerable to the impacts of human activities, such as natural resource exploration and extraction. Not only do these activities generate noise and pollution, but they often bring with them long-term camps of workers, attracting predatory mammals and birds to areas where they were previously absent (3). Climate change is also believed to be affecting the ivory gull's habitat. A significant amount of data now suggests that sea surface temperatures are rising in Arctic seas, while the thickness and extent of sea ice is decreasing, causing a reduction in the pack ice that the ivory gull so heavily depends on for much of the year (3). Furthermore, as ivory gulls scavenge on marine mammals, they are potentially susceptible to high levels of toxic pollutants accumulating in their bodies. For example, research on eggs collected from Seymour Island, Canada, showed that levels of mercury steadily increased between 1976 and 2004, reaching levels which are now among the highest measured in sea bird eggs. These levels of mercury are believed to be high enough to have detrimental effects on the ivory gull, such as impaired reproductive success (3). Finally, in Canada, the ivory gull is still hunted (3). Despite the population declines and numerous potential threats, the ivory gull is only classified as Near Threatened as in some areas the status of the ivory gull is poorly known and further surveys are required in order to determine the true scale of population declines (4).
Sources and Credits
- (c) Blake Matheson, some rights reserved (CC BY-NC), http://www.flickr.com/photos/34328261@N02/5155415422
- (c) Hans Olofsson, some rights reserved (CC BY-NC-ND), https://www.flickr.com/photos/hans_olofsson/6780872343/
- (c) Wildscreen, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/2603219
- (c) Wildscreen, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/5669822
- (c) Wildscreen, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/5669823
More Info
Range Map
iNaturalist.ca Map
| Animal | Bird |
|---|---|
| Color | white |
| Bird | gull |
