Roberval, Grove Warden

You may exile Roberval, Grove Warden as it attacks. When you do, create X 1/1 blue Bird creature tokens with flying tapped and attacking, where X is the number of basic lands you control.
At the beginning of the next end step, exile those tokens and return Roberval, Grove Warden to the battlefield under its owner's control.
" -Be my sense and sight! Yield me wisdom! "