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The number of red grouse (Lagopus lagopus scoticus) shot in the UK has declined by 50% during the 20th century This decline has coincided with reductions in the area of suitable habitat and recoveries in the populations of some avian predators. Here we use long-term records of shooting bags and a large-scale manipulation of raptor density to disentangle the effects of habitat loss and raptor predation on grouse populations. The numbers of grouse harvested on the Eskdale half of Langholm Moor in southern Scotland declined significantly during 1913-1990 and grouse bags from the whole moor from 1950 to 1990 exhibited an almost identical but non-significant trend. Hen harriers (Circus cyaneus) and peregrine falcons (Falco peregrinus) were absent or bred at low densities on this moor throughout this period but heather-dominant vegetation declined by 48% between 1948 and 1988. Harrier and peregrine breeding numbers on Langholm Moor increased to high levels following protection in 1990 whilst grouse density and grouse bags declined year after year until shooting was abandoned in 1998. The prediction of a peak in grouse bags on Langholm Moor in 1996 based on the patterns of bags during 1950-1990 was supported by the observed peaks in 1997 on two nearby moors with few raptors which formerly cycled in synchrony with Langholm Moor. This study demonstrates that, whilst long-term declines in grouse bags were most probably due to habitat loss, high levels of raptor predation subsequently limited the grouse population and suppressed a cycle. This study thus offers support to theoretical models which predict that generalist predators may suppress cycles in prey populations.

We compared techniques to assess diet at 17 Hen Harrier (Circus cyaneus) nests. Diet was measured directly from observations and compared to estimates from pellets, prey remains and a combination of pellets and remains. For data pooled across nests, pellets over-represented mammalian prey and under-represented avian prey. Prey remains over-represented large prey and under-represented small prey. Combining pellet and remains data did not eliminate these biases. Pellets gave higher diversity values than direct observations and detected more small prey species. For data analyzed on a nest by nest basis, estimates from pellets were significantly related to estimates from direct observations for three prey types by frequency and all types by biomass. These linear relationships were used to predict frequencies and biomass of prey types in the observed diet at five new nests. Our findings suggest that pellets are useful for estimates of prey diversity and as an index of the frequency of certain prey types in the diet, but direct observations are necessary to help quantify the biases inherent in diet estimates.

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The diet of red fox Vulpes vulpes was investigated through analysis of 340 scats collected during 1992‐1996 from moorland in south‐west Scotland. Rodents, game‐birds, lagomorphs, carrion and insectivores were the most frequently occurring food types. Fox diet and prey abundance were compared between heather dominant and grass dominant habitat types within the study area. Rodents were the most frequently occurring food type in each habitat and occurred in 63% of seats overall. Rodents occurred more often in scats from grass dominant sites while gamebirds and lagomorphs were more frequent in scats from heather dominant sites. The occurrence of rodents in winter fox scats increased with rodent abundance. In contrast, the occurrence of gamebirds in winter fox scats was unrelated to gamebird abundance but negatively related to rodent abundance. It appeared that foxes switched to gamebirds in years, or habitats, where rodents were uncommon.