BODY-MASS, WING LENGTH AND SPRING ARRIVAL OF THE ORTOLAN BUNTING EMBERIZA-HORTULANA

In this study, individual and sexual differences that may affect the t ime for spring arrival of Ortolan Buntings in southern Sweden are anal ysed. The median arrival date was, on average, about one week earlier in males than in females. We found that males with longer wings arrive d before males with shorter wings. This applied in normal weather cond itions as well as in a spring with prevailing cold northerly head-wind s. In females, we found no correlation between wing length and time of arrival. In head-wind conditions the arrival of both sexes was delaye d, and the first males arrived with lower body masses. Females arrived with a larger body mass in relation to wing length than males. It is briefly discussed what are the functional factors connected to wing le ngth that may be of importance for the time of spring arrival. In male s, body size, age, and flight performance are possible factors. In fem ales, the individual date of spring arrival is evidently determined by other factors than those correlated to wing length.