Comparative Food Habits of Red Grouse in Northeast Scotland, Using Fecal Analysis

Food habits of red grouse (Lagopus lagopus scoticus) were studied, by comparing analyses of plant remains in the feces with vegetation, on two moors over limestone andover granite in lower Deeside, Kincardineshire, Scotland. Feeding trials were conducted with captive birds to see if the proportion of identifiable material varied with different species ingested, and to calculate correction factors for estimating actual proportions eaten. Heather (Calluna vulgaris) was the main plant on both areas. On the granite area, where other plants were scarce, heather was the main food eaten throughout the year. On the limestone area, other plants were more common and were available particularly in summer. There, the grouse diet was again mainly heather in winter but the birds ate some of the alternative foods available in summer. These results are compared with other data on population regulation of this species in relation to food. In this study, food habits of red grouse were compared on two moors lying over limestone and granite, where the vegetation was more varied on the limestone than on the granite. The chief food of red grouse is heather and the important questions asked were: (1) would the birds eat mainly heather on both areas, and (2) would they alter their diet to take some of the more varied food available on the limestone area? A secondary aim was to find whether food habits varied between individual grouse territories. We tried to answer these questions by analyzing feces. Undigested cuticular fragments were identified in the feces by the appearance of cell walls and patterns of cells, as each species had characteristic features (Prat 1932, Winton and Winton 1932, quoted in Martin 1964). Others have used similar techniques for herbivores, including Swanson (1940) for sharp-tailed grouse (Pedioecetes phasianellus), Godfrey (1953) 1 Present address: Wildlife Research Division, Fish and Wildlife Branch, Agronomy Road and Main Mall, University of British Columbia, Vancouver 8, Canada. 2Present address: The Nature Conservancy, 12 Hope Terrace, Edinburgh 9, Scotland. 612 for voles (Microtus agrestis), Peters (1958) for willow ptarmigan (Lagopus lagopus), Hercus (1960) and Martin (1955, 1964) for domestic sheep, Williams (1969) for cattle and millipedes (Glomerus spp.), and Zyznar and Urness (1969) for deer (Odocoi eus spp.). The latter authors list additional references. We thank V. C. Wynne-Edwards for encouragement and criticism; W. N. Charles provided advice about fecal analysis; A. Watson gave valuable suggestions and critically reviewed the manuscript; G. R. Miller helped with botanical and statistical aspects; C. Elston and G. W. Eaton suggested statistical treatment of fecal analyses, and S. Douglas permitted us to work at Tilquhillie.