D7000 lose shadow detail
There are several factors that can affect shadow detail in JPEGs with the D7000. D-lighting settings, exposure compensation, ISO value (which affects dynamic range), and I'm sure more that I can't recall right now.
I suggest, if you're serious about photographing birds (and other wildlife), that you get Thom Hogan's guide to the D7000 which will cover these matters and much more.
To be clear, I've no connection to Thom except one of great admiration for all the help his guides have given me over the years through a succession of Nikon DSLRs.