you can buy shapes of other birds- any shapes in fact and it works. Have a look at the RSPB on-line sales. Our bird feeders are close to the window near the settee where I read, watch tv and spend too much time on line - and it really does work.
Birds use to fly into the window at great force and knock themselves out- and at times died. I hope that woodpecker would be OK, but some of the brain damage caused means they won't recover and die later. Best frighten them a bit- and keep them safe. Our feeders today, near the shapes- had sparrows (both kinds) chaffinches, bramblings, goldfinches, bullfinches, a great spotted woodpecker, several kind of tits- and even some starlings ...
as said, have a look at RSPB website to see what is available.
We do have a visiting sparrow hawk or two- so they get feed too- somehow, but that is nature.