The ecology of black grouse Tetrao tetrix in North-East England
Habitat and dietary preferences and ranging behaviour were assessed from January 1989 to May 1991 in the nearly treeless Pennine uplands at Allenheads, using radio-telemetry, transect walks and faecal analysis. Male home range size was smaller than female (maximum 455 hectares). The population density of 0.07 birds/hectare was average for Black Grouse. Mortality was mainly due to predation. On four occasions (N=15) radio-tagged hens did not breed. Chicks fed predominantly on invertebrates in their first two weeks of life, with vegetation predominant thereafter. Sawfly larvae (Symphyta, Tenthredinidae) were of overriding importance. Lepidoptera larvae, sawfly adults, parasitic hymenopterans, C-laterid and r-hrysomelid beetles and bibionid flies were also significantly preferred. Adults took a wide variety of ground vegetation. In winter males took much Heather Calluna vulqari , when hens additionally took quantities of monocotyledon leaves. In spring, cotton grass Eriophorum vaginatum was important, particularly for hens. Considerable quantities were taken by cocks in some nearby areas. In summer and autumn, flowers, fruits, seeds and berries, particularly of Common Catsear Hypochaeris radicata, buttercup Ranunculus spp., Common Mouse-ear Cerastium fontanum, Heath Rush Juncus squarrosus and Crowberry Empetrum niqr were important. Bilberries Vaccinium myrtillus, although fairly widespread, were not taken. Invertebrates formed a small proportion of adult diet. Diet and habitat were closely interrelated. In autumn and winter, heather moor was used most, with grassland habitats also important. Some birds frequented open conifer plantations, but tree-feeding was only once observed (Hawthorn Crataegus monogyna). In spring and summer, grassland habitats were important for all birds except non-breeding hens, which remained in heather moorland. Nests were mainly in rushes Juncus effusus, with some in heather. Rushes were important chick habitats. Management guidelines, including rotational heather burning, smallscale tree-planting and the adoption of sympathetic farming practices, are suggested.