Very good book that explains how iceages on earth aids the evolution of birds, how birds follow SUN in daytime, Stars in the night time, if it is cloudy and are flying on Sea how they can use earth magnetic field to find thier way. This book explains where birds breed in the spring-summer times and migrate to warmer places in fall-winter. As the morning SUN warms up the ground, the air heats up. The birds use this rising hot air help them in soaring to new heights.
This book engineers bird migration, explains how migration evolved, how birds decide the time of travel, how they use the natural phenomina like thermal soaring, how the wing shape and size are related to its flight - like sea birds have long, thin wings, geese have heavy wings etc.
Then this book talks about specifics like how swans migrate, Geese migrate, Albatross migrate and you can find specifics about sea, land, north american, eurasian birds.