Leisure activities as a main threat for the conservation of waterbirds in an estuary in northern Iberia

Human disturbances can have a severe impact on avian conservation, decreasing diversity and carrying capacity of ecosystems. Coastal wetlands are hotspots for the conservation of biodiversity but they commonly suffer the impact of human activity because they are usually priority areas for socio–economic development. The aim of this study was to determine the role of several factors on the potential and real disturbances of human origin on waterbirds over an annual cycle, and to evaluate their impact on the waterbird community. The study was carried out at the Urdaibai estuary (Spain). Although Urdaibai is a main coastal refuge for aquatic birds in Northern Spain (a Ramsar site, Natura 2000 site, Reserve of Biosphere), it faces high levels of human–induced disturbances. We found disturbances varied across the day, week and year, with peak disturbance coinciding with hours, days and months with highest activity, mostly associated with leisure options. The impact on waterbirds varied between species and the response to such impacts was also species–specific. Disturbances were highest near the river mouth and decreased towards the upper parts of the estuary. Efforts to increase protection of waterbirds should consider reducing the disturbance in areas with the highest impact in order to increase the functional carrying capacity of the estuary for waterbirds and to create quiet feeding and resting areas, maybe by establishing reserves with restricted access.