Barometers are great tools for letting you know the air pressure is dropping and a storm's on-the way. But they're not the only way to make predictions. Hi I'm Dave Thurlow and this is the Weather Notebook. Nature, it turns out, has devised another way to give us the heads-up on coming bad weather. Here's a hint: it involves feathers. Correspondent Jeff Rice reports.
There's an old saw that birds will roost just before a storm. Dr. Roger Lederer, head of the Ornithology department at California State University at Chico, says there is some acadmic support for that bit of folklore.
"Nobody really knows what the scientific mechanism is...what's the bird's sense organ for a low pressure. But we've heard about peoples' knees as you get older sensing the weather, so perhaps it's the same kind of mechanism. But birds will sit around and if you see a lot of them sitting on a wire somewhere, you can expect a storm is coming."
They sit, says Lederer, because storm systems make it harder for birds to fly. Lower air pressure means the air molecules are more spread out. This makes the air thinner.
"Think about it in a very simplistic way. Think about trying to swim in air versus swim in water. If you jump into a pool with no water, you're just going to go right down to the bottom. Cause there's just no molecules there to push your arms against. And the same thing with birds. With thin air it's difficult to push their wings against the air and they're going to do things as efficiently as they can and that means flying with the least amount of impediment or bad weather."
In the Spring and Fall especially, bird migration will tend to follow weather patterns to take advantage of the best flying conditions. Often the best time for bird watching is before or after a storm.
That's correspondent Jeff Rice from Idaho. Thanks today to to Weather Notebook producer Margaret Landsman and engineer Sean Doucette.