Halting and reversing declines of black grouse populations in Britain represents a major conservation challenge. Programmes of dedicated management aiming to benefit black grouse have been introduced on several sites and areas across the species’ British range. These initiatives generally employ various managements, most aimed at improving habitat conditions, but some at reducing direct sources of mortality. Black grouse populations appear to respond to such conservation initiatives, with increases in numbers following the introduction of management in all six cases examined. However, these increases were not always sustained, and the frequent lack of control sites and baseline data means that there is limited ability to assess the full impact of management, and to distinguish management effects from the effects of coincident environmental variation. Similarly, it is difficult to identify the specific managements critical to producing black grouse response. Evidence exists for benefits of reducing large herbivore densities and of reducing generalist predator abundance, although these may be temporary in the case of herbivore reductions. Variation in annual productivity appeared to be a major determinant of population trends at two sites where productivity estimates were available, suggesting that responses to management may often arise via effects on productivity.
The alternative prey hypothesis suggests that generalist predators switch from their primary prey to secondary when the former is scarce. We tested this hypothesis during a two-year study combining data on predation of ground dummy nests and the numbers of small mammal populations in a highly fragmented landscape in the Krušné hory Mts, the Czech Republic. A significant decrease of small mammal numbers between 2002 and 2003 was followed by a considerable increase of predation on artificial nests from 34% to 76%. Most of the nests (64.7% of the documented cases in 2002) were predated by medium-sized mammals such as marten and fox, common in our study area. Only 8.8% were predated by avian predators (corvids) occurring infrequently in our study area. The results support the alternative prey hypothesis and suggest that in the Krušné hory Mts the nesting success of ground nesting birds may vary strongly from year to year depending on the cycle phase of small mammals, the main prey of dominant predators.