Distance to landfill and habitat cover predict colony size in a Western Mediterranean white stork population

Artificial food subsidies like landfills generate very strong impacts on animal ecology and spatial behavior. Landfills indeed have been considered to be one of the most influential factors explaining the very fast recovery of many colonial waterbird populations worldwide, as documented for the white stork Ciconia ciconia . More recently, the increase of rice fields in some regions have also been argued to be part of an influencial process underlying the spatio-temporal distribution patterns of this species over many areas in southern Europe. It remains unknown whether these two habitat factors play an important role at explaining the spatial distribution pattern of the white stork and, more particularly, whether colony funding or colony size is dependent on them. Using data from a census conducted in 2018, we aimed to assess the effect of distance to a landfill or to rice fields, among other habitat factors, on the breeding colony size of a white stork population in northern Spain. Larger colonies were more likely to appear in trees or cliff, but less likely in buildings or other artificial substrates. They were also significantly more likely with decreasing distance to landfill, and when the habitat was dominated by dry cropland and meadows close to water bodies. Rice fields did not seem to have any significant effect. Our findings fit with those from other regions in Europe, and highlight the effect landfills have on population dynamics and spatial ecology for those species which are able to feed on this type of food subsidy. Our results also show that the main habitat cover over large geographic scales still plays a role independently of landfills. The European agricultural policies associated with the type and management of crops, and the Common Agricultural Policy in particular, will still have a decisive role for the species.