Local Weather Conditions Affect Migration Strategies of Adult Western Honey Buzzards Pernis apivorus Through an Isthmus Area

Local weather conditions affect migration strategies of adult Western Honey Buzzards Pernis apivorus through an isthmus area. Zoological Studies 49(5): 651-656. We tested the effect of crosswinds, barometric pressure, and time of day on the visible migration of adult Western Honey Buzzards Pernis apivorus through an isthmus area in southern continental Italy. Simultaneous observations from 3 posts were made in autumn 2005 and 2006, and birds were assigned to one of 3 local migration corridors: western, central, and eastern. During our observations, prevailing winds were perpendicular to the direction of migration. The peak of migration occurred during the afternoon and with westerly winds. Ideal weather conditions for soaring flight occurred during weak winds and high barometric pressure. An analysis of migration frequencies among the 3 corridors suggests that adult Western Honey Buzzards tend to compensate for deviations in lateral winds on a small scale when migrating through this isthmus area. It appears that they do not slow their travel speed during weather conditions that are unfavorable for soaring flight (strong lateral winds and low barometric pressure) by increasing the use of powered flight. On the other hand, migrants will change their migration strategy in relation to wind drift when migrating through the Channel of Sicily en route to Africa, thus showing a broad front of migration over water.