I am mostly going to talk about navigation and physiology of migration. It's not uncommon for passerines to cover 1000 km/day, therefore, many Canadian migrants probably make their first landfall south of South Dakota after fueling up in the forests of eastern Nebraska. We need adverse weather to bring them down here. This is similar to what happens in Louisiana where you have what is called a Coastal Hiatus. In good conditions in the spring, birds take off from the Yucatan at dusk and make landfall in Louisiana well north of Baton Rouge. In bad weather, the birds crash down on the Louisiana coast. After several days, they take off and probably make their next landing well north of Louisiana. Therefore, much of the inner coast of the state sees few migrants, unless a cold front goes by just when the birds are overhead. In most of the USA, a sunny fall is not good for bird watching.
What is migration? Migration implies a return trip seasonally. The record holder is probably the Arctic Tern = 10,000 miles from the North to the South Atlantic. Penguins walk, some geese begin walking because they molt all their flight feathers at once. There is also elevational migration, up and down mountain ranges.
WHY DO BIRDS MIGRATE?
HOW DO BIRDS ORIENT?
THE PHYSIOLOGY OF MIGRATION
WHAT ABOUT BIRDS THAT DON'T MIGRATE--HOW DO THEY COPE?