According to data from the 1960s, northern pintails (Anas acuta) fly north of the Alberta and Saskatchewan prairies during drought resulting in decreasing pintail annual production. Reanalysis of overflight and reduced-production hypotheses using data from 1961-92 indicated that, although the same basic relationships were present, these relationships changed over time. The number of pintails counted in northern survey areas from Alaska through northern Alberta divided by the number in southern areas of Alberta and Saskatchewan was used as an index of overflight (North-South ratio). Variation in total May ponds in southern Alberta and southern Saskatchewan accounted for variation in the North-South ratio during the 1960s (r-2 = 0.779, P = 0.004) and 1980s (r-2 = 0.251, P = 0.08), but not during the 1970s (r-2 = 0.001, P = 0.94), generally a period of high total May ponds. Variation in the North-South ratio accounted for variation in pintail production, measured as the age ratio from hunter harvest (harvest-age ratios), during the 1960s (r-2 = 0.688, P = 0.01) but not during the 1970s (r-2 = 0.226, P = 0.14) and 1980s (r-2 = 0.103, P = 0.29). The lack of a relationship between harvest-age and North-South ratios during the 1980s resulted from lower average age ratios during years when large numbers of pintails were in the southern region. Pintail production in prairie-parkland areas may have declined and, in the 1990s, may be equal to production in the northern regions.
Additional publication details
Response of northern pintail breeding populations to drought, 1961-1992