From a recent AP Science Article:
Nuthatches appear to have learned to understand a foreign language — chickadee. It's not unusual for one animal to react to the alarm call of another, but nuthatches seem to go beyond that — interpreting the type of alarm and what sort of predator poses a threat. When a chickadee sees a predator, it issues warning call — a soft "seet" for a flying hawk, owl or falcon, or a loud "chick-a-dee-dee-dee" for a perched predator.This is something I've mentioned to my psych students before, though it's all been theoretical-- the idea that language for birds can translate across species when a predator is involved. I'd always suspected that they had very different language for "ground predator" vs. "sky predator" but never took the time to confirm it.
The "chick-a-dee" call can have 10 to 15 "dees" at the end and varies in sound to encode information on the type of predator. It also calls in other small birds to mob the predator, Christopher Templeton of the University of Washington said in a telephone interview.