d7100, the smaller birds in flight.
Nice job catching those little buggers.
Like you I have been out trying to take small bird in flight photos with my new D7100. I have it paired with the 70-300 af-s VR.
I have found that the 51 point autofocus seems to work pretty well for birds on uniform backgrounds, like blue sky. But it seems lousy if you have backgrounds with structure. In that case I have been dropping back to single servo/single point. Did you play around with the different AF settings on these birds?
Also, I am seeing lots of noise in the sky at 100% crop, even down at ISO 320. I am shooting raw and then doing noise reduction after processing so it ends up looking pretty clean. My main drawback is the softness of my lens at 300mm and f5.6.
I am seeing quite a bit of noise in your photos as well, granted at ISO 1000. Did your photos have any noise reduction?