Lesser Snow Geese an indicator of wildlife sustainability in the Georgia Basin

What is Happening?

A relatively large population of Lesser Snow Geese (Anser caerulescens caerulescens) nests on Wrangel Island, Russia, north of the Arctic Circle. These geese spend the winter (October - April) in North America. Roughly half the birds go to Central California and the remainder winter on the Fraser River (BC) and Skagit River (WA) deltas. This latter group, known as the northern sub-population, is a relatively closed one and is largely separate from the group in California. The Fraser/Skagit sub-population has been censused intermittently since 1948 but it has only been since 1987 that consistent accurate air-photo surveys have documented abundance and recruitment rates.

Source: W.S. Boyd, Pacific Wildlife Research Centre, Environment Canada, Delta, B.C. 2005. Values are computed from several photo counts conducted between December and March each winter. Total represents total number of adults and young. Harvest represents the total number of geese (adults plus young) taken by hunters on the two deltas each year.

GRAPH DATA

Between 15,000 and 20,000 more Snow Geese occurred on the deltas in the 1980’s and 1990’s compared to the 1950’s to 1970’s. Since 1987-88, the Fraser/ Skagit sub-population has fluctuated between 40-70,000 birds and is considered to be relatively healthy and stable.

The value of reliable abundance and recruitment estimates, achieved with air-photo counts, can be seen in the graph above. Note that the number of adults increases whenever recruitment exceeds harvest in the previous year. Whenever the reverse occurs, the number of adults declines. Such patterns are important to our understanding of long-term population dynamics and development of management prescriptions.

Source: S. Boyd. Canadian Wildlife Service. 1995. Data from air-photo counts in 1991-92; other years similar.

GRAPH DATA

The Fraser/Skagit sub-population moves exclusively between the two deltas, and does not winter elsewhere. Geese are found on both deltas throughout the winter except between mid-January and late February when all geese move to the Skagit delta. Note that when geese leave the Fraser delta the same number move into the Skagit delta. This pattern has been confirmed with radio-telemetry.

Why is it Happening?

The number of snow geese harvested by hunters in the Fraser and Skagit deltas each year is usually less than 10% of the population. Recruitment of young into the population (mean = 15%; range = 0-50%) accounts for most of the annual variability in abundance. Weather conditions on Wrangel Island, which are highly variable and can be severe in some years, influence recruitment. Over the last six years, however, summers have been drier and warmer. The increasing trend in numbers of geese wintering in the Fraser/Skagit deltas may be a result of global warming and improved nesting success (see Climate Change Indicator). Although not nearly as important as weather, fox predation on the nesting and molting areas and hunting on the Fraser/Skagit deltas are other factors influencing the population dynamics. The relative stability of this west coast population is in sharp contrast to mid-continent Snow Goose populations which have grown to the point where they are damaging their arctic breeding grounds.

Why is it Significant?

The Wrangel Island Lesser Snow Goose population is of international importance. This is the only population of Snow Geese wintering in North America that breeds on a separate continent and they have been "red-listed" as a species of concern in Russia, being the only remaining population in Asia. Within BC the species is not considered at risk, but is on the provincial "yellow list" because their seasonal concentrations make the species potentially vulnerable.

Source: S. Boyd. Canadian Wildlife Service.1995

These Snow Geese are also important to the Fraser and Skagit ecosystems as they play a significant role in the ecology of marsh plant communities. Research has shown that if Snow Geese are excluded, bulrush marshes increase in density by 2-3 times in only four years. In the Canadian Arctic where Snow Goose populations have exploded, vegetation damage has been so severe that wildlife officials are calling for population culls. However, due to the relative stability of the Wrangel Island population, and other factors intrinsic to the ecology of bulrush marshes, overgrazing is not yet an issue on the Fraser and Skagit deltas.

What is Being Done?

Tidal marshes and adjacent uplands on the Fraser and Skagit deltas are important to the geese for food and loafing sites. Because of the importance of the Fraser/Skagit deltas for both farmers and waterfowl, Canadian and US governments have a responsibility to implement appropriate harvest and habitat management prescriptions, and balance these initiatives with agricultural demands. They also must ensure that other important habitats used during the breeding and staging periods are protected.

On the Fraser River and Skagit River deltas, some habitat has been secured and is being managed to provide for the geese. Apart from the purchase of habitat, the Delta Farmland and Wildlife Trust, in conjunction with the Canadian Wildlife Service, provides seed to local farmers to plant cover crops for waterfowl. These cover crops also provide food for the birds while minimizing impacts on cultivated fields.

In 1976, Russia designated Wrangel Island as a nature preserve, in part to protect the goose population. More recently, Canadian, Russian and American biologists have initiated research on the wintering, staging, and breeding ecologies of the geese and a management plan has been developed to monitor the abundance, recruitment, and harvest rates of the Wrangel Island geese each year.

For more information contact: Sean.Boyd@ec.gc.ca

Check the following sites for additional information on this indicator:

• Canadian Wildlife Service (CWS) Hinterland Who's Who - Lesser Snow Goose
• CWS - Over Abundant Snow Goose Populations

The following Web sites are not under the control of Environment Canada (EC) and they are provided solely for the convenience of users. Environment Canada is not responsible for the accuracy, currency or the reliability of the content. Environment Canada does not offer any guarantee in that regard and is not responsible for the information found through these links, nor does it endorse the sites and their content. Users should be aware that information offered by non Government of Canada sites that are not subject to the Official Languages Act, and to which Environment Canada links, may be available only in the language(s) used by the sites in question.

• Bibliography of literature on Arctic Geese
• US Fish & Wildlife Service - Snow Geese
• US Fish & Wildlife Service - Report on the Arctic Goose Habitat Working Group
• USGS - Snow Goose Population Problem

For references cited in this indicator click here.