Night sky orientation of migratory pied flycatchers raised in different magnetic fields

Summary To test whether the initial night sky orientation response of migratory pied flycatchers (Ficedula hypoleuca) is calibrated from the ambient magnetic field experienced by birds during their first summer, three groups of pied flycatchers were hand-reared and then held under different magnetic field conditions during the course of the summer. All groups were held outdoors and given full exposure to the day and night sky. One group was exposed to the local earth's magnetic field. A second group was exposed to a magnetic field of local earth strength, local earth inclination shifted 105° counter-clockwise relative to the local earth's field. The last group was exposed to a vertical, and thus nondirectional magnetic field.In autumn, the birds were tested for their orientation under the night sky in the absence of a directional magnetic field. When tested, all three groups were oriented with mean directions varying from south to southeast. No statistical differences emerged in any between group comparisons. The data indicate that earth's magnetism does not serve as a calibrating reference in the development of a pied flycatcher's initial orientation response to the night sky.