Why Is The Sky Blue is a regular series of articles in which guys who understand really complex scientific things try to explain those things to not particularly complex people – your kids. Next up is Joe Duff, the co-founder of Operation Migration, which teaches migratory birds that are born in captivity where they’re supposed to go each winter and how they’re supposed to get there. He’s credited with helping develop the concept of “imprinting” migration patterns on birds by flying alongside them in ultralight aircraft. If he can figure that out, he can probably explain why birds fly south each winter using kid-sized words, right?
Your Kid’s Questions
Why do birds fly south for the winter?
Because they can. Birds use flight to their advantage in all sorts of ways, like flying away from animals that want to eat them, or to look for food. Generally speaking, in the winter, there’s more food for them further south. But, in the summer, there are better places for them to have baby birds further north. So, lots of birds go back and forth every season. Not all birds do that, though, and those that do don’t necessarily go north to south – the Trumpeter Swan goes west to east, from Alaska to the Chesapeake Bay.
Terns that nest in Greenland routinely log annual migrations of more than 44,000 miles.
Why do they fly in a “V”?
The lead bird is the boss of all the other birds – that’s the most aggressive one, that thinks it can fly the best. Every time that bird flaps its wings, it makes the air behind it easier to fly through, so the next most aggressive bird falls in behind the first one. The third most aggressive bird falls in behind that one, and so on, all the way down both sides of that “V”. The air at the back is the easiest air to fly through, so that’s where the most tired birds go. When the first bird gets tired, it falls back to easier air, and that’s how the whole flock stays together. How fast they fly depends on the species, but most migrating birds fly between 20 and 50 miles per hour. Ducks and geese regularly get up to 60 miles an hour, and some kinds of pigeons have been clocked at 70.
How do they know where to go?
Scientists don’t know for sure, but there are a lot of ideas. Some seem to know from the moment their born, while others appear to learn the directions from their parents, but they ultimately can memorize the route. There’s also a chance that birds can read the earth’s magnetic fields – a portion of their brain actually responds to magnets – as well as the position of the sun and the stars in the sky. Basically, they use every method of navigation humans do, they just don’t mess with Google Maps because they don’t have opposable thumbs.
Which bird has the most badass annual migration?
The Arctic Tern flies from the edge of the Arctic Circle to the Antarctic, and the shortest possible route is 12,000 miles. But they rarely take the shortest route because the way they travel such long distances is by utilizing prevailing winds to save energy. Terns that nest in Greenland routinely log annual migrations of more than 44,000 miles. Because they usually live into their 20s, it’s not uncommon for a Tern to log over a million miles in a lifetime. They still can’t get find available awards seats on United, though.