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Seasonal and Annual Trends in Numbers of Alberta Ruffed Grouse

Donald H. Rusch and Lloyd B. Keith
The Journal of Wildlife Management
Vol. 35, No. 4 (Oct., 1971), pp. 803-822
Published by: Wiley on behalf of the Wildlife Society
DOI: 10.2307/3799791
Stable URL: http://www.jstor.org/stable/3799791
Page Count: 20
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Seasonal and Annual Trends in Numbers of Alberta Ruffed Grouse
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Abstract

Estimates of spring populations of ruffed grouse (Bonasa umbellus) on a 4-square-mile area (Main Area) near Rochester, Alberta, increased from 112 grouse in 1966 to 124 in 1967 and to 164 in 1968. Data from smaller study areas and provincewide questionnaires showed similar trends. In 1966 and 1967, grouse populations declined rapidly throughout November, but numbers were stationary between December and the following spring. Approximately 36, 42, and 23 percent of the males present in 1966-68 did not establish territories. The numbers of grouse produced (308 and 330) were similar in 1966 and 1967, and survival of juveniles (< 3 months of age) throughout the brood period was the same (51 percent) in both years. The distance between capture sites of drumming males averaged 86 yards between successive springs. The mean distance between capture and recovery sites of young females (3-12 months of age) was 1.8 miles in the fall. At least 80 percent of the juveniles present on the Main Area in August subsequently dispersed in September and October and were replaced by ingressing young grouse. Survival rates of young were 0.42 and 0.67 from fall to spring, and 0.21 and 0.34 from hatching to spring, in 1966-67 and 1967-68, respectively. In these years, annual survival rates were 0.42 and 0.41 for drumming males and 0.27 and 0.30 for all adults (> 12 months of age). Predation on grouse, mainly by great horned owls (Bubo virginianus), lynxes (Lynx canadensis), and goshawks (Accipiter gentilis) accounted for more than 25 percent of the annual mortality and for more than 80 percent of fall-to-spring mortality each year. In the fall, predation was selective toward males and young but not toward smaller versus larger grouse. As populations of snowshoe hares (Lepus americanus) increased rapidly between 1966 and 1969, great horned owls consumed relatively more snowshoe hares and relatively fewer ruffed grouse. It was this shift in predator food habits that allowed higher survival of young ruffed grouse and was thus responsible for increased numbers of grouse in the spring.

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