Biological Bird Navigators - Page 2

The second hypothesis proposes that birds may be able to extract latitude and longitude from the earth's magnetic field. Unlike the compasses that are thought to help birds determine direction, this map is believed to help birds determine location. The main support for this hypothesis comes from observations of pigeons released in areas of "magnetic anomalies" (places where the earth's magnetic field is distributed due to large iron deposits near the surface). When pigeons are first released in these areas, they depart in random directions, but after their initial confusion, most birds are able to correct their course and return home once they escape the influence of the anomaly. Because, in theory, magnetic anomalies are not a strong enough force to affect any of the birds' compasses --- magnetic, sun, or star -- proponents argue that the fact that the pigeons are initially affected indicates the existence of a different aspect of navigation that is being affected -- hence, the map.

Neither hypothesis has been proven to the satisfaction of all the experts, so new and different experiments continue to be performed. It may turn out that neither of these alternatives is correct, or a synthesis of the two may emerge.