Biometrics, sex ratio and migration periods of reed buntings emberiza schoeniclus wintering in the tajo basin, Spain

Abstract

We analysed capture and biometric data of 2, 408 Reed Buntings Emberiza schoeniclus ringed at Carrizal de Villamejor, Tajo Basin, Central Spain. Reed Buntings showed a clear sexual size dimorphism; males had longer wings and were heavier than females. Body condition, as determined from the residuals of a regression of weight on wing length, was highest in males, particularly during midwinter. Mean wing length, especially of the males, decreased over the winter, probably due to feather wear and abrasion, but possibly also due to older and larger males departing earlier. Maximum mean weights were recorded in spring pre-migratory periods and minimum weights occurred in October, during the final stages of autumn migration. Female:male ratios were 3:1 in the population during winter. The ratio was at a minimum in October and at a maximum in March, which suggests that females arrived and left later than males. The earliest males arrive at Carrizal de Villamejor in autumn approximately 10 days before the earliest females, and also depart in spring 10 days sooner. © 2003 British Trust for Ornithology.