Book excerpt: From the slums of Cape Town to the palaces of Algiers, through Pygmy villages where pineapples grow wild, to the Gulf of Guinea where the sea blazes with oil flares, across two continents and fourteen countries - this epic journey is nothing to swallows, they do it twice a year. But for Horatio Clare, writer and birdwatcher, it is the expedition of a lifetime. Along the way he discovers old empires and modern tribes, a witch-doctor's recipe for stewed swallow, explains how to travel without money or a passport, and describes a terrifying incident involving three Spanish soldiers and a tiny orange dog. By trains, motorbikes, canoes, one camel and three ships, Clare follows the swallows from reed beds in South Africa, where millions roost in February, to a barn in Wales, where a pair nest in May.