Weatherwatch: How do racing pigeons find their way back home?

http://www.guardian.co.uk/news/2012/oct/28/weatherwatch-pigeons-racing-tracking

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Racing pigeons are normally very reliable, so much so that every plane going on a raid in the second world war carried one, which would be released with a grid reference attached to alert rescuers if a crew was forced to ditch. Since pigeons fly as fast as 60mph, many were home quick enough to save lives. Some birds went missing, and still do so, taken out by predators like peregrine falcons, but it is rare for a large percentage of birds competing in a race to fail to return.

When it does happen, weather conditions are often blamed. Fog, rain and high winds are said to affect performance, and single racing birds, travelling fast in poor visibility, do hit telephone and power lines although this does not explain large numbers of pigeons getting lost. There is disagreement about how pigeons navigate. They are "trained" by owners transporting them gradually longer distances from their loft and letting them go to find home.

When tracked, these birds use familiar landmarks, rivers, motorways and hills to locate home, so fog and low cloud is a handicap. Over longer distances birds are said to use the position of the sun or stars as an aid. But there is also scientific backing for the theory that pigeons use the magnetic field of the earth to navigate. That has gained credibility because some large recent losses of pigeons have coincided with the Sun's periodic surface storms, which in turn disturb the Earth's magnetic field.