Common Tern I think? Forrester's breeding range is in the area. For the Common Tern seeing it would be on migration here. I haven't seen a bonafide fresh juvenile yet though.
I encourage photographer's to push the ISO. I didn't want to go above ISO 800, and for the longest time I didn't. I've heard others say the same thing. So when you get into a situation were you need a higher shutter speed just go for it. F9 1/2000 ISO 1600 at 500mm