Dear Bird Folks,
I know that many birds avoid our cold winters by flying to South America, only to return in order to breed during our summer. What I’d like to know is, are there any birds that breed in the Southern Hemisphere and fly to North America during our summer, not to breed again, but to avoid their winter? If not (and I assume the answer is no), why not?
– Noah, New York University
Noah, At first I was glad to read your question. It’s not often that I get a question that doesn’t involve wanting to know the correct formula for hummingbird food (four parts water to one part sugar) or the proper size entry hole for a bluebird box (1-1/2″). Yours is a question that I’ve never been asked before, making it the first virgin question I’ve had in years. However, the wind went out my sails when I read that you were from N.Y.U. That ruined everything. Now that I know you are a super-smart college guy, I can’t use my usual double talk and vagueness. I may actually have to do some research this time. I hate doing that. I wonder if there are any libraries around here. Do we even have libraries anymore? This isn’t going to be easy. I’d better put on the coffee.
I wasn’t kidding when I said this a good question. When you think about it, why don’t birds fly up to North America to get away from the winter in Southern Hemisphere? The weather is nice here in the summer and there are other things to do besides breeding, I guess.
South America beats North America in many ways. It has higher mountains, drier deserts, nastier snakes, and its beaches have hotter looking sunbathers. But good old North America has one thing its southern neighbor doesn’t have – a killer winter. Without a killer winter the birds of South America aren’t forced to leave. Oh sure, South America technically has a winter, but it’s a little weenie winter when compared to ours. I don’t care if it is closer to Antarctica and has tons of penguins, when it comes to winter we rule and South America knows it.
If you look at a map you’ll notice that South America resembles an ice cream cone. It is wide at the top and tapers to a point at the bottom. And just like an ice cream cone, most of the good stuff in South America is at the top. When you get to the skinny tapered bottom, there isn’t much going on. Before you Patagonians start complaining, I know you have lots of wonderful bird life, but it’s nothing compared to the avian diversity that thrives in the vast rain forests to the north. It’s not your fault. You are just don’t have the land mass to support a huge variety of birds. You are skinny and there isn’t much you can do about it.
The birds of the rain forests and tropical regions to the north live in such a stable environment that they don’t ever have to leave. Things are pretty darn sweet for them 24/7/365. As you head south, toward the bottom part of the cone, the weather isn’t as stable and can become a bit nasty during the winter. Luckily for them, the birds that do need to get away from the cold don’t have to go that far. They only have to fly to tropics in the northern half of the continent where they’ll find all the warmth they need. Movement from south to north is called an “austral migration.” Pretty fancy term, eh? See what happens when I’m forced to do research?
The Andes mountain range is the major geographical feature of the western edge of South America. Some birds like what they find in these rugged mountains, so instead of migrating north to south, or south to north, they simply make an altitudinal migration. They move to the higher elevations during the summer, and then return to the lowlands when weather turns bad. There’s nothing really exciting about this kind of migration, I just thought you’d like to know about it.
You are mostly correct, Noah, when you thought southern breeding land birds don’t venture into North America during their winter. There is plenty of food and warmth for them on their own continent. But I said you are “mostly correct” because some South American swallows and martins will migrate as far north as Central America and Mexico. I’m only mentioning that because I was once reminded that Central America and Mexico are really part of North America and I don’t want to get yelled at again.
The next question, after all of this, should be: If things are so swell and wonderful in South America, why do millions of birds make the dangerous migration to North America each spring to breed? That’s a good question all right, but I’ve done enough research for one year. I have to get out of this library before someone I know sees me. Besides, I think the librarian is hitting on me, and he is so not my type.