one can never have enough focal length for doing bird photography & I was concerned about the hit I would take with a FF camera
fortunately my old 300 mm with the excellent 1.7 TC gets me to about 500 mm, but I suspect I will be wanting a longer lens still
maybe in the spring if all goes well
in the mean time, I just moved the feeders in a bit closer
full resolution crops follow in my D3X gallery here ------> http://www.pbase.com/artichoke/d3x&page=1