The first one is really exceptional. Gulls are very common where I spent the weekend, but I discovered that shooting them with an AF lens is different than shooting with manual focus. I got no keepers of birds in flight (sigh). And here you post a whole series!
Harriet, I didn't post the other 200 that were out of focus....:-) Seriously, in-flight shots with AF introduces a different set of problems than MF. When a larger bird, like this gull, goes above the tree line, the AF doesn't have a hard time locking on since the bird is the only contrast area in the sky, but when they're flying in front of a background of trees, it's a real challenge to keep the focus point on the bird instead of the AF system locking in on all those potential focus points in the back. (most of the ones I erased were beautifully focused on hardwoods on the bank of the river) I far prefer AF because I can't seem to make the fine adjustments necessary to get a good focus with the Bigma while the bird is in flight. And, there's nothing so frustrating as hearing that whirring noise when the lens suddenly decides to go searching. BTW, I had 13 that I kept out of more than 200 shots of this gull.
Thanks to all for the nice comments on the gull series. Most of the in-flight shooting I've been doing lately has been hawks, and you're lucky to get off three or four shots before they're out of range. It was nice to have a subject who just kept circling and giving me multiple opportunities.