Abstract
Roadside surveys of Loggerhead Shrikes Lanius ludovicianus, originally established in 1987, were replicated in Saskatchewan in 1993 and 1998 and in Alberta in 1998. In Manitoba, the two survey routes that had shrikes on them in 1987 were replicated in 1993, but not in 1998. In Alberta, the mean density of shrikes was 3.8 times higher in 1998 than in 1987. In Saskatchewan, shrike densities increased from 1987 to 1993 and declined from 1993 to 1998. Although differences were not statistically significant, overall trends between 1987 and 1998 appeared more stable in the western half of Saskatchewan and less stable in the eastern half of the province. In Manitoba, the shrike density on the two resurveyed routes was 39% lower in 1993 than in 1987. Independent surveys in Manitoba revealed a 58% overall decline from 1987 to 1999. These results suggest that, since 1987, the population of Loggerhead Shrikes has increased in Alberta, remained relatively stable in Saskatchewan, and declined in Manitoba. Analysis and interpretation were limited due to observer changes, weather effects, and the inherent biases of roadside surveys.
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