Red grouse populations on experimentally treated and untreated Irish bog.
On flat bog with deep peat where heather (Calluna vulgaris), the principal food of the birds, was scarce application of superphosphate, or ground mineral phosphate, plus K2SO4, CuSO4, MnSO4 and cobalt sulphate (together with draining and fencing) increased the productivity and nutrient content of heather and its coverage of the ground. Grouse density in spring increased five-fold. Grouse reared larger broods and concentrated on the treated plots. On a hill where heather was more abundant but was heavily grazed, fencing to keep out sheep and cattle resulted, within a year, in improved growth of the heather and in colonization by grouse.