Long-Term Population Trends of Colonial Wading Birds Breeding in Doñana (Sw Spain) in Relation to Environmental and Anthropogenic Factors

Summary. Breeding season counts of nine species of colonial wading birds (Nycticorax nycticorax, Ardeola ralloides, Bubulcus ibis, Egretta garzetta, Ardea cinerea, Ardea purpurea, Ciconia ciconia, Plegadis falcinellus and Platalea leucorodia) nesting at Donana during 1984–2010 were analysed. The aim of the study was to assess the size and trends of populations and to analyse their environmental and anthropogenic determinants. We used the TRIM programme to test for long-term trends, and Generalised Additive Models to assess the effect of local rainfall, the surface area of ricefields surrounding Donana and rainfall in the Sahel on breeding population size. All species showed positive population trends, mainly from 1996 onwards. The number of active colonies increased over time, and up to 17,297 nests from the nine studied species were recorded in one year (2010). Low precipitation (< 500 mm) in the previous autumn and winter was associated with reductions in the numbers of breeders, since rainfall determin...