I have learned to listen to the birds to tell what is going on in nature.
In 1981 Roy Stone and I were walking on a trail while backpacking in Glacier National Park when the birds went silent. The silence was very eerie. A moment later we met a two people who said that they had just seen a grizzly on the trail ahead of us. My weariness evaporated immediately and I experienced a surge of alertness – we didn’t see the grizzly but I could feel a powerful presence.
Around our home, we find that blue jays are very effective at communicating the presence of predators. (They probably listen to the chickadees.)
Chickadees use one of the most sophisticated signaling systems discovered among animals. The calls warn other chickadees not only if a predator is moving rapidly, but also transmit information on the degree of threat posed by stationary predators of different sizes.