How and why birds navigate the skies, travelling from continent to continent has continually fascinated the human imagination, but only recently have we been able to fully understand these amazing journeys. This is the never-before-told story of how an eccentric group of ornithologists, engineers and other pioneering scientists have harnessed nearly every technological development of the last 100 years to understand bird migration in detail - from where and when they take off, their flight paths and behaviours, their destinations and the challenges they face getting there. Rebecca Heisman uncovers the secret history of an ornithological arms race that not only helped solve the mystery of bird migration using radar, radioactive isotopes, satellites and the humble aluminium band but has also given us much needed insight into how best to protect and conserve the bird life we cherish.