I have a follow-up question to my Minor Upgrade thread in which some replies mentioned specific lenses that would be good for wildlife. Is there an unwritten rule that you should avoid mixing brands of bodies with lenses? They make adaptors that don't cost all that much so I'm wondering what the drawbacks are to putting a Nikon lens on a Canon. The reason I'm asking is I have a line on a pretty nice used Nikon lens designed for wildlife and if I can't find a decent Canon/Tamron lens on my budget for the 80D I expect to buy after Christmas, I would consider making him an offer.