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By Arthur T. Bergerud, Michael W. Gratson

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Additional resources for Adaptive Strategies and Population Ecology of Northern Grouse (v. 1 & 2)

Sample text

In this sense, I accept the arguments of Hjorth (1967) and others, linking territorial and reproductive displays to aggression. These threatening patterns were virtually always used less by grouse in the increasing population than by those in the stable or declining ones. Spontaneous song apparently did not align with other behaviors of territorial ownership. However, unlike other behaviors, it not only was elicited by an intruder to which 26 D. H. MOSSOP grouse were forced to react, but occurred without intrusion and was measurable, Bendell and Elliott (1967) stated (as I found) that grouse hoot more often in dense populations and explained it as simply a result of the birds stimulating each other more in dense populations.

Again there was no significant difference between the two low areas. Flushing distances were longer at the high area in each sex and age category. A related phenomenon was the time it took for a grouse to flush after first being disturbed, and the distance it walked or ran before flushing. Once again in the increasing population, significantly fewer grouse took more than 2 minutes to flush and fewer moved 20 m or more than those at the other two areas (see also Mossop 1971). 16 D. H. MOSSOP Fig.

Our indexes included: whether the female "led" us away or approached us; the distance moved while displaying; the number of times a hen flew by us (passes) when we played chick distress whistles; and the length of time she remained in the area. We had no measurement of female aggressiveness until 1975, when we recorded a cackle call of a hen attacking a dummy in a mirror arena on Stuart Island (Bergerud & Butler 1985). The cackle call apparently had an aggressive function and was later played to measure answering responses as an index of aggressive behavior.

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