Hi all. I'm looking at getting a long telephoto zoom lens for birding, air shows, wildlife and maybe also sport. The lens will be used predominately hand held. I have narrowed the selection down to the following:

Canon 100-400 EF f/4.5-5.6L IS USM, 1,380g - approx $1,850
Sigma 50-500mm f/4.5-6.3 APO DG OS HSM, 1,970g - approx $1,550
Sigma 150-500mm f/5-6.3 APO DG OS HSM, 1,910g - approx $1,000
Tamron 150-600mm f/5-6.3 SP VC USD Lens, 1,951g - approx $1,300

At the moment, I am leaning towards the two Sigmas, as they are longer, and cheaper, that the Canon. They also both have pretty good user reviews on the net. The Tamron sounds good, but it hasn't been out long enough for many user reviews to be posted on the net.

If anyone has any experience with any of these lenses, or has an opinion on which would best suit my purposes, any advice would be greatly appreciated.

Thanks,

Neil