A female northern wheatear with a light level geolocator attached to its back, in a picture by Heiko Schmaljohann of the Institute of Avian Research Wilhelmshaven, Germany, released on February 15. The tiny songbird -- weighing just two tablespoons of sugar -- migrates from the Arctic to Africa and back, a distance of up to 29,000 kilometres (18,000 miles), scientists reported.