Researchers have determined that nuthatches are able to understand warning calls by chickadees. Depending on the type of warning call given, the nuthatches reacted in different ways.
The researchers played recordings of chickadee calls and observed the reaction of the nuthatches. A warning call about a small predator resulted in different behavior than from a large-predator warning call. This demonstrated that the nuthatches not only heed the warning of the other bird, but understood details about the warning.