Alarm Calls – Early Warning System
Ambience: Mobbing call, black-capped chicadees
Greene: Our research is giving us some insight into how many different species are participating in these amazing distant early warning systems.
When birds see a predator nearby, like a hawk, they’ll produce alarm calls which can warn other birds and other animals of the danger. Scientists studying these alarm calls are learning that they’re remarkable effective. I’m Jim Metzner and this is the Pulse of the Planet.
These alarm communication networks are far more sophisticated than scientists had previously suspected.
Erick Greene is a biology professor at the University of Montana.
Greene: Mobbing calls are alarm calls that are given when a bird sees a hawk that is perched – that is sitting in a tree, for example. And mobbing calls tend to be really loud and very harsh and what we call broad band, and they travel very far and they’re very easy to localize. Mobbing calls are signals that send out the alarm – they call in the troops. This is a very highly directional signal. It’s easy for all the other critters in the woods to know exactly where that threat is.
What you’re hearing now is a flock of black capped chicadees. They discovered a pygmy owl that is a major predator of chickadees. Many other species came in to help with the mobbing. What we’re finding is that a lot of these sounds have very specific meanings to the other birds that are listening in. They’re sharing lots of information with this huge diversity of sounds.
Eric Greene and his colleagues have been discovering a kind of universal language of alarm calls. We’ll hear more in future programs. Pulse of the Planet is made possible in part by Virginia Tech, inventing the future through a hands-on approach to education and research.