Here you see an American crow perched at the top of a bare spruce as a sentinel (lookout). He’s loudly warning his family members that are feeding in the field below that I’m approaching: “ah-ah-ah! / caw-caw! / ah-ah-ah!”
These intelligent birds have a complicated vocabulary of at least 20 calls that can be intermixed with varying emphases to convey many different meanings. In captivity they reportedly have been known to correctly mimic more thatn100 sounds.
Crows often post sentinels while the rest of their group (often called a “murder” of crows) conducts a joint activity or is resting together. This is especially so in the winter when several families rest and feed together for safety; the greater the number of eyes and ears when they’re in leafless trees, the safer it is. Crows often post more than one sentinel when the rest of their murder is spread out.
Not only crows benefit from their early warning system. Other birds and mammals go on alert when they hear a crow sentinel’s warning squawks, especially squirrels and other small mammals. (Images taken in Brooklin, Maine, on September 2, 2026.)