Flipping navigation

摘要

Reading about the mechanisms by which animals use magnetisn for navigation (27 November, p 4: prompted me to wonder how they cope when the Earth's magnetic poles reverse, which happens on average every 300,000 years. Not only would the poles reverse, but the field strength would weaken during the time of change, perhaps being close to zero for a period of time. Such events would presumably cause mayhem for migrating birds, marine life and insects. Is there any evidence of this?