Magnetic Fields and the Orientation of Homing Pigeons Under Sun

Applying a magnetic field of 0.1 Gs (1 gauss = 10-4T) to the heads of pigeons homing from unfamiliar release sites significantly increased the scatter of the birds' vanishing bearings. A magnetic field of 0.3 gauss caused no difference between the orientation of birds wearing coils with either their north or south pole up. But a field of 0.6 gauss (equal to that of the Earth) produced a small difference in the vanishing bearings of the two groups. Since an applied magnetic field has an effect on pigeon orientation under sun, it appears that pigeons do not simply switch between a magnetic and a sun compass, but that there is some interaction between the two systems.