Why do birds migrate? Ask the man who’s followed them.

No matter where you are on earth, unless you’re near the poles, countless migrating birds have been passing overhead this spring. Kenn Kaufman, author of birding guides, uncovers the mysteries of this extraordinary phenomenon in his latest book, A Season on the Wind: Inside the World of Spring Migration. He spoke with The Christian Science Monitor recently. 

Q: What makes migration so remarkable?

It’s an amazing feat of endurance and navigation – billions of birds moving great distances twice a year. And it’s largely invisible. Of course, I’m biased because I’m captivated by birds in general. I’m most drawn to how they’re so intensely alive, even when they’re sitting quietly.

Q: Why do birds migrate? 

Some birds nest during the summer in places where they couldn’t possibly survive through the winter, so they’ll fly thousands of miles to the tropics.

Q: Why don’t they just stay where it’s warm?

Even the most remote regions of the Arctic are overflowing with abundant life in summer. Once things thaw out, there are wildflowers everywhere and an abundance of insects. It becomes worth the effort for the bird to fly a long distance to go back there and raise its young.  

Q: What role does radar play in birding? 

Birders regularly look at Nexrad [Next Generation Weather Radar] on apps on our phones to see what’s happening in terms of migration overnight. This gives you a rough sense of how many birds are moving. 

So many of the small birds migrate at night – warblers, vireos, orioles, songbirds. We can look [at the radar] and see if tomorrow is a good time to go outside. Most of these nocturnal migrants will come down around dawn wherever they happen to be. If there’s been a big movement overnight, it’s exciting to go out and see what’s come in.

Q: You write about a battle over bird-killing wind farms. How do you view wind power?

It can be really effective and an important source of green energy. But in some places, wind turbines can kill a lot of birds. We’re concerned about having good preconstruction studies to determine which areas are the most risky for bird populations. In some places, such as major stopover habitats for migratory birds, they kill so many birds that they become a genuine conservation issue. 

Q: How is climate change affecting migration?

It’s already starting to have some impact. We know that some of the migratory birds are coming back earlier in the spring and leaving later in the fall. In some cases, the timing has put the birds out of sync with local conditions. They may be coming back a week earlier while the trees are leafing and the insect populations are peaking at a different time. Some species will be able to adapt and change rapidly, and some won’t. 

Q: If it’s warmer everywhere, will fewer birds need to migrate?

That’s one way to look at it, but the effects are not uniform. We have changes not only in temperature but also in rainfall patterns. Things are becoming more extreme. 

Q: If you could be a migrating bird, which would you want to be?

I’d be proud to be a migrating blackpoll warbler. It’s a tiny bird that weighs about half an ounce and looks like the dullest bird in the flock. But ... they can fly hundreds or even thousands of miles without stopping. I’ve seen them in eastern Peru, and they may have just flown in from the Yukon Territory. And when they go back, they can find their way to the same tree.