Ecology and Reproduction of Red-Shouldered Hawks in the Waterloo Region, Southern Ontario
A study of Buteo lineatus was done in 1973 for the Canadian Wildlife Service in south-central Ontario. Six pairs were studied in the Waterloo Region for habitat requirements, behavior (especially breeding and feeding), interspecific competition, and reproductive success. In 1973 two (and perhaps three) pairs raised young, two deserted, and two outcomes were not definitely known. Other aspects of reproductive history were deduced from past notes and Ontario Nest Record Cards for the Waterloo Region and surrounding counties. A decline in nesting numbers was noted over a period of 10 years. Loss of habitat and prey, and increasing raptorial competition, seem to be causing a decline in this species. Three eggs were analyzed for residues of organochlorines and mercury. Eggshell thicknesses were also recorded. Thickness index was calculated for 70 eggshells from this area. A 14.5 percent decrease in eggshell thickness has occurred since 1947.