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Warning

In addition to songs, most birds have one or more calls they use to signal danger to other birds nearby. These calls can be loud and harsh.

You might hear an alarm call
if you startle a bird or get too close to its nest. The call might be announcing that you've been spotted in the area.

If you were a predator, the
call might be a small bird telling other small birds to come quickly and "mob" you. (The mobbing birds would flock around and flap their wings at you, not hurting you but generally pestering you into to leaving the area.)

Some birds have different calls depending on whether the danger is something approaching from the ground – like a snake – or from the air – like a hawk. Red-winged Blackbirds have seven different alarm calls.

The Black-capped Chickadees have a whole language of alarms. A cry of "seet" means there's an overhead predator. Crying "chicka-dee" means the threatening bird is perched rather than in flight. A call of "chicka-dee-dee" warns that the predator is large. "Chicka-dee-dee-dee-dee" announces that the predator is small and agile – the type of predator who is most dangerous to chickadees. The more "dees" a chickadee uses in the alarm, the greater the danger.

Red-breasted Nuthatches are about the same size as chickadees. They've learned to understand chickadee alarm calls, and even though they have their own calls for alarm and mobbing, they will react just as the chickadees do when they hear a chickadee warning. This eavesdropping can be lifesaving.

Chickadees seem to know other birds are listening in, though – they sometimes give false alarms so other birds will leave the area and they can have the local food to themselves.