Black-capped Chickadees may be the easiest birds to identify by ear. Chick-a-dee-dee-dee, they sing, telling you exactly who they are. (I’ve heard that towhees do this too, but the towhees I’ve heard always seem to be saying twee or taree, from which I would not be able to get “towhee” unassisted.)

Of course, the chick-a-dee sounds like a vocal nametag to us only because someone had the good sense to name chickadees after their call. But it serves as an identifier among the chickadees too. The “chick-a-dee call complex” consists of four note types (the A, B, C, and D notes in a row might be transcribed as chick-k-ka-dee) that can be given in various combinations. Each note type itself can vary in frequency and duration. The chickadees thus have a lot of potential variation to work with, and they do. The D (dee) notes alone indicate both the identity of the individual bird calling, and the flock it belongs too—rather the same way that an Englishman saying “Hello, my name is George,” might indicate to compatriots both his own identity (George) and, in his accent, the region he is affiliated with. When captive chickadees are put into new flocks, the calls of the new flock members change, converging on each other, to indicate their new flock membership.

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