Differential spring migration of Ortolan Bunting Emberiza hortulana by sex and age at Eilat, Israel

Abstrakti

The Ortolan Bunting in Europe is considered vulnerable and large declines have been reported. However, there is little information pertaining to the wintering grounds and the migratory part of the annual life cycle of the Ortolan Bunting across most of its range. We analysed data collected during 1984-2000 at the only long-term ringing station in the Middle East - at Eilat, Israel. Difference in passage dates between sexes was significant, but small in comparison to differences reported on the breeding areas. However, we found no differences in arrival dates between age classes. We found significant differences in wing chord length between the four sex and age classes (adult males, 1st year males, adult females and 1st year females). Also significant differences in body mass were found between the four age and sex classes. Young females were lighter than other birds. Wing length and body mass did not affect arrival date of birds. We suggest that the discrepancy of arrival dates between the sexes at Eilat and at the breeding grounds can be explained because males are time-minimizer migrants that attempt to reach the breeding grounds in the shortest time possible. On the other hand, females appear to be energy maximizers and try to reach the breeding grounds in good physical condition. It is possible that the males make fewer stops while on migration between Israel and the breeding grounds in Eurasia.