I started this in response to an answer I gave a guy who seemed to be frustrated with the birds he was following in his boat. Here's my experiences. Remember there are lots of additional variations of what I have seen.
"When you see birds, try to classify in your mind what they are doing. Birds will organize themselves around bait, even if there are no fish feeding, so that's why you will see them sitting in the middle of the water sometimes.
The circling and sporadic diving signifies they have found bait they can reach, while just circling can signify they have found bait that is not yet accessible.
The easiest bird behavior to identify is when they are diving on fish that are blitzing, but as mentioned previously, there are other behaviors you can look for, and variations of the ones I mentioned, that will also help you to find fish. Hope this helps. "
If any one else has perspectives or experiences to add to this, I would appreciate hearing them.