The Sigmonster is really not the best choice for this - - but it's not like I'm not going to try & work at it. ;-)

Most of these are crops. The birds move around a lot & though zooming is possible, it's easy to zoom in & then have the bird exit the frame in a split second. I've not ever had so many shot with clipped this or that as I did after this first attempt of TIFs. I could but laugh......