Aspects of individual performance in red grouse

• Main Author: Lance, Arthur Norman
• Published: University of Aberdeen 1975
• Subjects: 591.5
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.592914

Differences in the breeding, survival, and social behaviour of individual red grouse are described for a population at low density during a fluctuation in breeding numbers. The aim was to identify aspects of the individual's upbringing which might be used for predicting his success or failure in joining the adult population. The basic premise was that differences in individual performance would be due to differences in the birds' nutrition. Three interrelated aspects of performance are considered: i) how and where the young cock competes for territory in autumn, in relation to his parentage and early development; ii) how the sur-vival and recruitment success of a brood compares with its nutritional background: and iii) whether the food in the parents' breeding territory is related to the size of that territory. Variation in the food was assessed by the percentage cover, N content, and height of the heather (Calluna vulgaris), which is the staple diet of red grouse. The histories of selected individual grouse were followed by radio-telemetry, beginning before nesting and extending for up to two years after. The main findings are: i) that young cock grouse from the same family returned during autumn to their parents' former territory, where they competed with one another and with their father for owner-ship of the parents' territory site: ii) that the success of the young cock in taking over the parents' territory was associated with his aggression, dominance, and early growth; iii) that the heather in the parents' territory was not used by the brood after hatching, and therefore had no direct effect on the individual cock's early development; iv) that the brood's early survival and growth were related to the heather in their parents' territory nonetheless, which suggests that its influence was indirect, probably via the quality of eggs laid by the hen; and v) that the heather available to the breed-ing hen was inversely correlated with the size of territory taken during the previous autumn by the cock. Other information is given on the selection of feeding sites by breeding hens, the behaviour of the brood towards predators, the behaviour of hen grouse during autumn, and the effectiveness of the radio-telemetry technique. A model is proposed which relates the individual's performance within any one year to the nutrition and performance of his family over successive generations. The conclusions about individual per-formance are discussed in terms of their possible adaptive significance, and suggestions are made for future research.