Summary 1.There is often a perceived conflict between recreational access and wildlife conservation. Although many studies have investigated the potential effects on birds, this is the first study to demonstrate an impact of recreational disturbance on population size. 2. We studied the impact of disturbance on a woodlark Lullula arborea population on 16 heathland sites in southern England. These sites all had historical records of breeding woodlarks and together encompassed a range of visitor-access levels. 3. A logistic regression model of patch use was used to quantify the area of habitat suitable for woodlarks. Woodlarks favoured patches with substantial proportions of bare ground and short vegetation. Across heaths, woodlark density (per hectare of suitable habitat) was lower on sites with higher levels of disturbance. Within heaths with recreational access, the probability of suitable habitat being colonized was lower in those areas with greater disturbance and was reduced to below 50% at around eight disturbance events per hour. There was no relationship between disturbance and daily nest survival rates. Birds on heaths with higher levels of disturbance fledged more chicks (per pair) because of a strong density-dependent increase in reproductive output. 4. A model is presented that predicts the consequences for the woodlark population of a range of access scenarios. The impact on the population depends on both the numbers of people and their spatial distribution. Under current access arrangements, a doubling of visitor numbers has little effect, while the same number of people distributed evenly across all sites leads to a major negative impact on the population. Density-dependent breeding success partially balances the negative effects of disturbance; however, we calculated that there is currently a 17% reduction in productivity compared with that predicted in the absence of disturbance. 5. Synthesis and applications . Many previous studies have stressed the negative effects of recreational disturbance on birds' behaviour, distribution and breeding success. However, from a conservation viewpoint, the impact at the population level is of paramount importance. Modelling the population-scale consequences of alternative access scenarios will help policymakers develop appropriate mitigation measures.

Summary 1.Losses of farmland birds from the wider countryside have become a major conservation issue in the UK and Europe. Song thrush Turdus philomelos populations in lowland rural Britain declined by approximately 70% during 1970-95, most severely on intensively managed arable farmland. Comparison between a stable population on mixed farmland and a rapidly declining population on arable farmland revealed fewer nesting attempts each summer by birds in the declining population, and annual productivity was insufficient to maintain local population density. Inadequate food resources were the most plausible cause. 2. We compared breeding season habitat selection (using radio-telemetry) and earthworm availability (a major component of summer diet) for song thrushes in the same two farmland populations. 3. Territory settlement in the mixed farmland landscape involved the selection of field boundaries and woodland and the avoidance of arable crops. Field boundaries and gardens were selected in the arable landscape, while arable break crops and small areas of woodland were avoided. 4. Habitat selection (intensity of usage) did not change through the breeding season and did not differ between study areas. Scrub, woodland edge, wet ditches and bare soil in gardens were preferred foraging habitats, while cereals were avoided. 5. Habitat utilization (amount of usage) differed markedly between study areas. Woodland and grassland accounted for 53% of all habitat usage in the mixed farmland landscape compared with just 13% in the arable landscape. Gardens and arable crops were more heavily utilized in the arable landscape, accounting for 58% of all usage compared with 22% in the mixed landscape. 6. Earthworm availability declined markedly between April and June as surface soils dried out. Lower earthworm availability in the arable landscape was associated with more rapid and pronounced drying of surface soils. 7. Synthesis and applications. Lack of woodland and grassland, and the faster drying of surface soils in the arable landscape, combined to limit the availability to thrushes of key summer invertebrate prey. Loss of hedgerows, scrub and permanent grassland with livestock, and the wide-scale installation of under-field drainage systems, have probably all contributed to the decline of song thrushes on UK arable farmland. New agri-environment measures may be needed to provide the nesting cover adjacent to invertebrate-rich damp soils that song thrushes require to sustain annual productivity.

No abstract

No abstract

No abstract