How do migrating birds find their way back home?
Re: What triggers bird migration & what keeps them on course? Navigation is the part of migration that has puzzled biologists the most. For some species, biologists still do not know how they navigate thousands of miles to the exactly same place every year. Nevertheless, there are four theories that are accepted the most by biologists. 1. Use of the sun: Birds, like humans, possess an internal circadian clock that allows them to track the daily light-dark cycle. Along with this internal clock, birds use the sun’s shadows to gain a sense of location. 2. Use of the stars: Because many birds migrate at night, the sun is not available as a guide. These nocturnal migrants have learned to use the stars for navigation. In the northern hemisphere, the constellations appear to rotate around the North Star. Birds can orient themsleves in relation to the North Star, and unlike the sun-compass, this “star-compass” is not time dependant. 3. Use of the earth’s magnetic field: Biologists have two dif
