Breeding losses of red grouse in Glen Esk (NE Scotland): Comparative studies, 30 years on

Abstract

Hatching success, brood survival and predation rates of red grouse chicks were examined at four sites in north-east Scotland over two years (1994--1995). Two of these sites have previously been the focus of a large-scale population study on grouse during the late 1950s enabling a comparison to be made. A total of 85 hens were radio-tracked and their breeding success monitored over the two years. Compared with studies undertaken in the 1950s, mean clutch size had risen from 7.2 to 8.6 eggs. Of the 76 nests monitored, 17 (22.4%) broods were lost either through egg or chick predation or by the adult being taken by a predator during incubation. Stoats appeared to be responsible for the largest amount of egg predation. There was a significant increase in predation levels, although hatching success was not significantly different from the 1950s. Chick mortality was highest within the first ten days, a similar result to that found in the 1950s. Overall, mean brood survival from hatching to 20 days was 55.1%. Possible reasons for larger clutch sizes, and the apparent increase in predation levels, are discussed.