Impacts of hunting disturbance on waterbirds - a review

Waterbird hunting is a widespread activity in wetlands throughout Europe and constitutes one of the most significant sources of disturbance during autumn and winter. The biological evidence for effects of hunting disturbance on the behaviour and distribution of migratory and wintering waterbirds and its possible impacts on population dynamics is reviewed. Most of the literature has been concerned with local effects of disturbance, focussing on quarry geese and dabbling ducks. Comparatively little is known about effects on diving ducks and waders, while there is no direct evidence for impacts at the population level for any waterbird species. Hunting disturbance can cause temporary disruption of normal activities of waterbirds, alter their diurnal rhythms and increase escape flight distances. It can displace waterbirds from preferred feeding and roosting habitats at local or regional level and increase turnover, so that the carrying capacity of a site is not reached. Quarry waterbirds, and those occurring in large inshore concentrations, such as many dabbling ducks, geese and waders, are potentially most sensitive to disturbance. Hunting disturbance can disrupt pair-bonds and family structures which may affect reproductive output. Evidence is provided that many waterbird populations are limited by winter conditions and that the majority of studied waterbird species lose body reserves during winter. Because hunting disturbance causes under-exploitation of potential feeding grounds where population limitation is considered to occur, such disturbance will, by definition, have an impact at the population level. However, the magnitude of this impact has not been quantified and requires a modelling approach.