The Influence of the Earth Magnetic Field to the Migratory Behaviour of Pied Flycatchers (Ficedula hypoleuca PALLAS)

Abstract

During autumn migration, Pied Flycatchers (Ficedula hypoleuca) like many other migrating bird species, have to change their initial migratory direction on reaching Portugal and south Spain from SW to SE to reach their central African wintering area (Zink 1977). While this Zugknick seems to be endogenously controlled in other bird species like the Garden Warbler (Sylvia borin, Gwinner and Wiltschko 1978), it was not to observed in Pied Flycatchers. While these birds were tested in the local geomagnetic field (0.46 Gauss, mN 360°, 66° Incl) without visual cues no change in the migratory direction or in orientation from the initial direction to SW after the 10th of October was observed, although Pied Flycatchers are able to orient with respect to the earth magnetic field (Beck and Wiltschko 1981). So it is fell that this bird species needs an external factor to change their migratory direction. The present experiments will prove whether the variation of inclination and force of the earths magnetic field along the migratory path of the Pied Flycatchers serves as this factor.