Quaker parrot

Q: My cockatiel yawns a lot. Is that normal?

–          Coralynn F., Bedford, Ma

A:   Yawning is a bit of a mystery. The reasons for it are not really fully understood, but there are some plausible theories as to why we yawn.

You may have noticed that yawning generally takes place during periods of inactivity. One theory suggests that fatigue causes breathing to slow and yawning increases our oxygen intake.

Another theory says that yawning expands the lungs and causes them to flex, similar to the way we stretch our arms and legs ...