Crow Vocalization and Posturing - Set 1

The bowing motion of the crows is a part of a behaviour I observed with a group of crows several years ago where I worked. The bowing was part of a vocalization effort. Having watched it many times, I suspect it's not inborn behaviour but learned, since the crows seem to practice it. My belief is the bowing is part of what's required to fill their throat sac with air. Then they let the air out in a stuttering fashion. I suspect it's a form of specific communication. This particular group of crows would respond when I would make a poor attempt of the stuttering sound.

I also suspect that this process is not an easy thing for crows to accomplish. Crows can caw readily with a beakful of peanuts, standing or flying. Yet, in order to create this rattling sound, they seem to have to go through an elaborate process that involves bowing.

American Crow (corvus brachyrhynchos)

The bowing process begins - taking in air into the esophageal (throat) pouch. You can see the throat pouch increase in size in the above three pictures (giving the appearance that the crow has a peanut or two stored away).

Letting out the air in a controlled way that gives a rattling or stuttering sound. The sound is totally unlike the typical 'cawing' made by crows. The rattling can vary from a soft quiet stutter to a loud, hard rattle that you'd not expect from a bird.