This audio story is brought to you by BirdNote, a partner of the National Audubon Society. BirdNote episodes air daily on public radio stations nationwide.
This is BirdNote.
A frantic cacophony of loud, rapid bird calls tells other birds nearby: There’s a predator on the prowl. Mobbing, it’s called, as birds clamor and dart back and forth at the threat.
An ongoing study of mobbing and other bird warning behavior now suggests that some birds listen in on the warnings of other birds. A wave of warning calls spreads from one hillside to another at more than 100 miles per hour. So vulnerable birds may be clued in to a predator’s movements before it comes near, giving them time to take cover. Even chipmunks and some squirrels seem to pay heed to the birds’ red alert.
The predator’s size might also be coded in the bird’s alarm calls. Chickadees announce an urgent alarm for a small, agile pygmy-owl that’s a major threat to them.
You’d think an eagle would cause a louder alarm, but no. Birds of prey are the greatest threat to other birds of similar size because they can best match them in a chase. So for the chickadee, the eagle prompts something much more like a polite yawn, maybe.
For BirdNote, I’m Michael Stein.
Today’s show brought to you by the Bobolink Foundation.
Bird sounds provided by The Macaulay Library of Natural Sounds at the Cornell Lab of Ornithology, Ithaca, New York. Black-capped Chickadee mobbing  recorded by R C Stein. Black-capped Chickadee call  recorded by M D Medler.
BirdNote’s theme music was composed and played by Nancy Rumbel and John Kessler.
Producer: John Kessler
Executive Producer: Dominic Black
Written by: Bob Sundstrom
Narrator: Michael Stein
© 2015 Tune In to Nature.org, July 2018