Hi Delta!,
I have Canon Elan7 (Also known as EOS30), and use it with Sigma 70-300mm/f4-5.6. and Sigma 28-90mm/f3.5-5.6. This is Not a Fast Lens ..but can manage with faster films. In your case (Digital camera) you don’t have to worry about it. But look for camera that can shoot multiple frames per sec and Faster lens (like say: 70-300mm/f4 ) or better still 500mm (non tele lens).
Since I own a Canon, I would recommend Canon 🙂 …it can also shoot 3fps (Frames per sec). Which you may want to do while for faster subjects.
Also suggest, you post a query at http://www.photo.net
Regards
Vignesh Baliga