Navigating with nature’s compass

BIRDS are great travellers.

Arctic terns visit both the top and bottom of the world, enjoying two summers each year, while the swallows arriving in Ireland just now have flown from South Africa.

Last year’s breeders will seek out the barn or shed they left last autumn. Swallows travel by day. They seem to have a map in their heads and use the sun as a compass. Songbirds usually fly at night, taking their bearings from the stars. But the travellers can still find their way when neither sun nor stars are visible and they do so in all weathers.