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UBC Theses and Dissertations

Lesser Snow Geese and agricultural habitat use on the Fraser River delta Bradbeer, David Ross


Lesser Snow Geese winter on the Fraser River delta of south-western British Columbia and feed on upland agricultural crops. With the recent loss of foreshore marsh habitat adjacent to the Vancouver International Airport, agricultural habitats have become more important. The loss of foreshore habitat, combined with a growing Snow Goose population, will increase the grazing pressure the birds exert on farm fields in West Delta. Because Snow Geese can overgraze perennial forage grasses, conflicts with farmers will likely escalate. Providing foraging opportunities for Snow Geese while minimizing the conflict between the geese and Delta farmers should be the goal of management efforts. To accomplish these goals, the Alaksen National Wildlife Area (ANWA) and Greenfields cover crop program must be managed in a way that attracts Snow Geese to these areas. From 1995 to 2000 Snow Geese used the Alaksen National Wildlife Area during both the fall and late winter hunting seasons. Fewer geese fed outside the Alaksen National Wildlife Area during open hunting seasons compared to when the seasons were closed. Snow Geese used perennial forage, cover crops, potato, and grain between 1995 and 2000. Between October 2005 and April 2006,1 documented patterns of agricultural field use on Westham Island and Brunswick Point and assessed how crop type, hunting, and field size influenced those patterns. I used foraging theory as a framework to assess how temporal changes in the quality and quantity of food influenced crop use. The main determinant of field use was crop type. Nutrient content appeared to be important to the order of crop use. Snow Geese used the crops that contained the highest concentrations of crude protein (cover crops) and simple carbohydrates (potatoes and barley grain) first in the fall and early winter. Perennial forage crops contained the highest concentration of indigestible crude fibre and were not used until the higher quality crops were depleted. Absolute crop biomass did not seem to influence crop use patterns because Snow Geese initially ignored perennial forage fields that contained more biomass than cover crop and potato fields. In March and April Snow Geese continued to use perennial forage fields, but also grain stubble and cover crop fields. Use of these fields may have been related to the presence of newly sprouting forbs and grasses. Snow Geese moved outside of the Alaksen National Wildlife Area despite an open hunting season in November 2005. Food depletion within the Alaksen National Wildlife Area may force Snow Geese to tolerate hunting pressure and was likely a factor that caused the geese to use fields outside the area.

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