- In the Arctic and Atlantic oceans, nesting seabird populations have generally increased since 1970. Some of these increases reflect a long-term recovery from historical over-hunting.
- In contrast in the Pacific, there has been a slight decline since 1980; introduced predators on nesting islands and other threats to breeding sites have had a negative effect on some species.
- Seabirds are particularly vulnerable to oil spills, mortality from fishing nets or hooks, and predators in their nesting colonies. In addition, their food supply is being affected by complex changes in ocean ecosystems due to climate change and large-scale commercial fisheries both inside and outside of Canadian waters.
Breeding seabird colonies in the Atlantic and Arctic have shown overall increases, partially reflecting a long-term recovery from historical over-hunting. Before the Migratory Birds Convention of 1916, harvest of seabirds and their eggs for food was widespread, decimating many populations and driving the extinction of the Great Auk—a large, flightless relative of murres and puffins. Seabirds live a long time and reproduce slowly, so their populations, once reduced, are slow to recover.
In Atlantic Canada, these long-term recoveries levelled off for many populations in the early 1990s, when changes in food webs linked to the crash of the Newfoundland cod population reduced available prey fish.
In the high Arctic, climate change may be having short-term benefits for seabirds by reducing the number of years when heavy sea-ice cover limits feeding. Conversely in the low Arctic, earlier ice break-up has adversely affected nest success in some species, including Thick-billed Murres. The long-term consequences of changing food webs are poorly understood.
The largest colony of Northern Gannets in the
world is on Bonaventure Island in the Gulf of
St. Lawrence in Quebec. Since 1976, the
number of pairs has increased from 16 000
to almost 60 000, partly a result of reduced
exposure to pesticides such as DDT. (photo:
No reliable monitoring data are available for the millions of seabirds that visit Canadian waters in their non-breeding season. However, monitoring data elsewhere indicate that some of these species are globally threatened, including the Short-tailed and Black-footed Albatross.
Aircraft are used to identify polluters after
oil slicks are detected by satellite surveil-
lance. (photo: Government of Canada)
Introduced predators kill adult birds, their eggs and nestlings in breeding colonies. Some colonies that formerly supported many thousands of birds have been abandoned. This has particularly affected species on the Pacific coast, including the Ancient Murrelet, a species for which Canada supports half of the world population.
Thick-billed Murres at many colonies have to travel farther
from their nests to find prey fish, due to ocean warming and
reduced sea-ice. (photo: Tim Lash)
Longline fishing kills seabirds—mostly albatrosses, gulls, fulmars and shearwaters—that attempt to feed on baited hooks or become tangled in lines. Diving seabirds drown when they are caught in fish nets. Common Murres and Rhinoceros Auklets are regularly killed in salmon gillnets.
Illegal oil discharges can be minimized through regular surveillance, including satellite and aircraft monitoring conducted by the federal government.
Atlantic Puffin with Capelin (photo: Paul Regular)
Unintended mortality from fisheries can be reduced by deploying streamers that scare birds from baited lines, by ensuring that lines and nets sink swiftly and by limiting fishing activities near large concentrations of seabirds.
Establishment of marine protected areas, improved management of fisheries and reduced carbon emissions will benefit marine birds by maintaining healthy food webs.
Red-necked Phalarope (photo: Charles Francis)
Oceans are important wintering habitat
During the winter, many birds move to marine environments, such as loons, seaducks, waterbirds that nest beside inland waters and shorebirds that breed in terrestrial regions. Shorebirds primarily congregate in inter-tidal areas while loons, seaducks, phalaropes and some waterbirds spend the winter in the open ocean. These species are sensitive to some of the same hazards as seabirds, including oiling and changes in sea-ice and food availability. They are also vulnerable to coastal habitat loss both within and outside of Canada.