The decline of the rook corvus frugilegus wintering population in spain: A new case of 'short-stopping'? | La graja corvus frugilegus deja de invernar en Espana: ¿Un nuevo caso de acortamiento en las migraciones'? the decline of the rook corvus frugilegus wintering population in Spain: A new case of 'short-stopping'?

Abstract

Wintering Rooks were commonplace in Spain at the beginnings of the 20th century. In the seventies the wintering population was still present in both the southern and northern plains and in the Ebro Valley. In the winter 2004-05, a maximum count of only 100 birds in two roosts was recorded, one in Valladolid and another one in La Rioja. In the winter 2006- 07, only a flock of 50 birds wintered in the Rioja. Migratory Rook populations tend to make shorter movements from the breeding sites to new, more northerly, wintering grounds. This means a definitive isolation of the Leon breeding population, making it more vulnerable.