How perception and density-dependence affect breeding Woodlarks Lullula arborea

There is often a perceived conflict between allowing recreational access to the countryside and wildlife conservation. Although many studies have investigated potential impacts on birds, few have assessed the potential impacts of recreational disturbance at the population scale. We studied the impact of disturbance on a Woodlark Lullula arborea population on 16 heathland sites in southern England (Mallord et al. 2006). These sites all had historical records of breeding Woodlarks, and together encompassed a range of visitor access levels. A logistic regression model of patch use was used to quantify habitat suitable for Woodlarks. Woodlarks favoured patches with substantial proportions of bare ground and short vegetation. Across sites, Woodlark density (per hectare of suitable habitat) was lower in sites with higher levels of disturbance. Within sites with recreational access, the probability of suitable habitat being colonized was lower in those areas with greater disturbance; this was reduced to below 50% at around eight disturbance events per hour. There was no effect of disturbance on daily nest survival rates. Birds on sites with higher levels of disturbance fledged more chicks (per pair) owing to a strong density-dependent increase in reproductive output.

J. W. MALLORD, P. M. DOLMAN, A. F. BROWN & W. J. SUTHERLAND, Ibis 149 (s1), 15-15