JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. British Ecological Society is collaborating with JSTOR to digitize, preserve and extend access to Journal of Animal Ecology. Summary 1. Previous work on red grouse (Lagopus lagopus scoticus) on a north-east Scottish moor showed that recruitment of young to the territorial population in autumn largely determined changes in numbers between springs. 2. This paper analyses territory locations of individually marked fathers and sons during a big cyclic-type population fluctuation in 1969-77. 3. In years of increasing numbers, sons took territories close to their fathers. When fathers did not keep their territories for another year, sons took territories on or close to their natal territories. In years of declining numbers, kin moved further from their natal areas to establish territories. This fits ideas that some animal populations comprise distinct sub-populations or demes. It is consistent with a model whereby changes in recruitment dependpartly on the size of such demes, and cyclic declines in numbers are due to greater strife because demes are smaller and neighbouring cocks less closely related than during the increase phase. 5. Over the winter, territorial cocks had a lower rate of aggressive boundary disputes with territorial neighbours which were close kin than with those which were not closely related. 6. During two population fluctuations, the rates of territorial cocks' song flights and boundary disputes in winter were related to the young cocks' relative recruitment rate to the territorial population. Thus, winter interaction rates were low in winters when enough young cocks had been reared in the population to supply the observed recruitment, and high when the observed recruitment must have included immigrants. 7. The dispute rate also tended to reach its maximum one year after peak densities, and then to decrease.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology. Abstract.Red Grouse (Lagopus lagopus scoticus) show unstable population dynamics.The number shot for sport at Rickarton moor in northeast Scotland, for example, has cycled with 10-11-yr periodicity since 1946. Here, demographic and other causes of a population cycle were documented from 1979-1989, and an experiment tested the prediction that removing some cocks during the increase phase would prevent a subsequent cyclic decline. Throughout the study, sport shooting was stopped on the area where the main work was done. During 1979-1982, before the experimental removal of cocks began, numbers over the whole moor rose from a trough at the start of the study. On the control area, the cyclic peak in 1983 was followed by a decline until 1988, as predicted in advance from models derived from a previous study elsewhere. On the experimental area, enough territorial cocks were removed each spring from 1982 to 1986 to prevent the population from attaining peak densities for five successive years, and no cyclic decline occurred. The removal of cocks resulted in similar numbers of hens being lost from the breeding population. The main demographic cause of population change on control (cycling) and experimental (cycle broken) areas was variation in the recruitment of young cocks to the spring population. On the control area, recruitment was related to cycle phase and breeding success. Changes in food, nitrogen metabolism, and parasite burdens could not explain the cycle. Demographic patterns were consistent with a model in which changes in age structure affected recruitment. These and previous results refute four hypotheses as necessary causes of population cycles in Red Grouse: (1) maternal nutrition, (2) a version of Chitty's genetic hypothesis, (3) hostparasite (caecal threadworm), and (4) predator-prey relationships. The hypothesis that age structure changes and associated behavior cause cycles by affecting recruitment and, thus, population change, remains unrefuted.

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.

No abstract