Conservation management of moorland: a case study of the effectiveness of a combined suite of management prescriptions which aim to enhance breeding bird populations.

摘要

Capsule: A specific suite of moorland management prescriptions had no clear positive impact on breeding birds over ten years. Aims: To test the expectation that a combination of grazing, and burning/cutting manipulations, the blocking of drains (affecting habitat quality and foraging resources) and the control of some predators (affecting survival and breeding success) will lead to an increase in numbers of breeding birds on 9.5 km2 of moorland in Scotland. Methods: General Additive Modelling was used to compare bird population trends at the managed site against a 'control' of moorland-specific background trends (spatially and temporally smoothed) derived from an extensive UK-wide bird monitoring programme. Changes in vegetation, the effectiveness of predation control and influences of disturbance were also examined to attempt to identify potential mechanisms for population size changes. Results: Breeding populations for most species showed either a more negative trend at the managed site (Red Grouse, Skylark and Meadow Pipit) or no significant difference was detected (European Golden Plover, Eurasian Curlew, Common Snipe and Winter Wren) when compared to moorland-specific background trends. Stonechats and Carrion Crows increased, despite the latter being actively removed as part of predation control measures. No general change in the vegetation was detected and no reasonable habitat-based cause for the observed declines in some species was apparent. There was also no convincing evidence for a negative effect on moorland birds of disturbance from a nearby mine. As crow control failed to stem their increase and with supportive evidence for a decline in the breeding success of Red Grouse, it is suggested that the control of predation was ineffective and may have contributed to some species declines. Conclusion: There has been wide advocacy of, and considerable resources (e.g. through agri-environment schemes) devoted to, moorland habitat management for birds and yet declines continue. However, there are practical difficulties of establishing management that is effective in increasing moorland bird abundance. It appears likely that in areas where those birds are vulnerable to predation and its control is not effective, expectations of increasing bird populations in response to habitat management alone may be unrealistic.