please post an image or two.

Birds?

How big are the plants?

Jean, Thanks. We found the culprit. A Caterpillar! The green one with black spots and the little "horn". Seems to be the only one... so far. The tomato plant are in large pots, so we thought possibly birds, but a close look exposed the little guy,

Jim

Sounds like a hornworm. They get enormous (4 inches long) and do a lot of serious damage once they get larger. Good you found it while it was still small.