EFFECTS OF CLIMATE-CHANGE AND LAND-USE ON DUCK ABUNDANCE IN CANADIAN PRAIRIE-PARKLANDS

Recent declines in the number of breeding ducks in the Canadian prairi e-parklands have been hypothesized to be due to loss of habitat to agr iculture. However, prairie-parkland also has experienced wetland loss to drought as well as to agriculture. If habitat restoration is to be implemented and monitored successfully, it is important to separate th e effects of anthropogenic changes to the landscape on duck population s from those caused by changes in climate. We used data from annual ai r-ground surveys and from precipitation records to develop relationshi ps between indices of abundance of each of 10 species of ducks and ind ices of wetland conditions during 1955-1974. We used these relationshi ps to predict annual abundance of each species during 1975-1989. We co mpared predicted and observed abundances over the period 1975-1989 to distinguish declines in duck abundance greater than those accounted fo r by drought alone and to determine the magnitude and location of real ''deficits'' in duck abundance. Average annual deficits within Canadi an prairie-parkland over the period 1975-1989 were estimated at 1.2 X 10(6) birds for both Mallard (Anas platyrhynchos) and Northern Pintail (A. acuta), 480 000 for Blue-winged Teal (A. discors), 190 000 for Am erican Wigeon (A. americana), 175 000 for Northern Shoveler (A. clypea ta), 50 000 for Gadwall (A. strepera), 10 000 for Green-winged Teal (A . crecca), 40 000 for Canvasback (Aythya valisineria), 25 000 for Less er Scaup (A. affinis), and 5000 for Redhead (A. americana). Overall, t he effect of agricultural expansion in the east on prime waterfowl hab itat since 1951 appears to have been negligible. There, as much as 90% had been already lost prior to 1951. In the west, however, where prim e waterfowl habitat was still relatively abundant in 1951, agricultura l development has encroached substantially. The relationship between t he lost area of the best breeding habitats and the size of population deficits for Mallards and Northern Pintails in the entire Canadian pra irie-parkland region was significant for both species (P < 0.0027 and P < 0.0001, respectively). Consequently, habitat restoration programs located where the highest quality waterfowl habitat and the lowest qua lity agricultural lands overlap most should have the greatest potentia l to affect recovery of breeding duck populations in the Canadian prai rie-parklands.