Well, the chickens won't destroy it in summer :-). I see two challenges, Hm. Firstly gunnera like a lot of water, ie a pond or bog to get their roots into. I suppose that you could construct something at the edge of the enclosure. Secondly, whilst the birds are not likely to destroy it during the summer, when it dies back in the winter the crown of the plant would be very vulnerable to the chickens scratching it to bits. You would need some sort of removable wire mesh cage to put over it until the following summer.

id just get some chicken wire and mould it round the growing tips in winter .i mite even make a bog garden for said gunnera then a moat which the ducks would love and then the chicken run and hut part .