A World on the Wing: The Global Odyssey of Migratory Birds.

The book tells some of the amazing stories of migratory birds, their challenges, their feats. Bird migration is still an area of ornithology where we have much to learn. There are birds who we know where they breed, but they vanish the rest of the year. It's only been in the past decade, with smaller GPS trackers and better radar, that ornithologist have been able to track their migrations. 

Some of these birds really are flying non stop for eight months of the year. They my occasionally dip into the ocean for a little food. The rest of the time they are soaring, held up by ocean winds.

Radar has let us understand the scale of migration. In the spring, billions of birds really are flying back to North America.

All good stuff.