Home is where you start from, but where is a swallow's real home? And what does 'native' mean if the English oak is an immigrant from Spain?

In ninety richly varied poems and illuminating prose interludes, Ruth Padel weaves science, myth, wild nature and human history to conjure a world created and sustained by migration - from the millennia-old journeys of cells, trees, birds and beasts to Geese battle raging winds over Mount Everest, lemurs skim precipices in Madagascar and wildebeest, at the climax of their epic trek from Tanzania, braving a river filled with the largest crocodiles in Africa.

Human migration has shaped civilisation but today is one of the greatest challenges the world faces. In a series of incisive portraits, Padel turns to the struggles of human displacement - the Flight into Egypt, John James Audubon emigrating to America (feeding migrant birds en route), migrant workers in Mumbai and refugees labouring over a drastically changing planet - to show how the purpose of migration, for both humans and animals, is survival.