Spain hosts a large part of the central/western-European Red Kite population in winter and so plays a major role in its conservation. As a breeding bird, the Red Kite is declining across much of Spain, although in the Basque Eurosiberian region it has of late experienced relatively rapid population growth, especially in the province of Gipuzkoa. As a consequence, the distribution and size of its population in this region is presumed to have increased. To update population data, a winter Red Kite census was conducted in 2020–21, which coincided with an international appeal (LIFE EuroKite) to monitor this raptor in winter. This paper analyses and discusses the results of this census, furthers knowledge of Red Kite distribution and population size in the Basque Eurosiberian region in winter, and evaluates its role as a wintering area for this species in Europe. We detected ca. 50 roosts used by a total population of up to 700 individuals. During a simultaneous census, the number of roosts used at the same time was ca. 30. The size of the roosts ranged from 1-2 to 145 birds. Overall, the contribution of the surveyed region to the Spanish wintering Red Kite population is small in absolute numbers (less than 1.5%). However, these numbers are important regionally and indicate a remarkable increase over the 373 birds detected during the previous national census (2013–2014). Some of these birds (roughly 10%) belong to local breeding stock, which is thus confirmed to be resident.

Arizaga, J., Olano, M., Novoa, I., 2022. Winter distribution and population size of the Red Kite Milvus milvus population in the Basque Eurosiberian region. Revista Catalana d’Ornitologia 38,1-8. https://doi.org/10.2436/20.8100.01.34