Bob & Diana McElroy / Photos / The View from Point Alexander Archive /
⇦⇧⇨
peregrine falcon in pursuit of an immature ringbilled gull

(photo by Bob: 2012-07-13 - explore) 

Uh Oh!   The bird on the left is an immature ring-billed gull. The bird on the right is a peregrine falcon. (Actually, there were two of them). But I don't think they were seriously hunting, only harassing.