I agree with thinfor's proposal.
Of course, it is in the best interest of the terns if no hiker land on the islands on any occasion. However, I believe that this can only be achieved by education. It is not an easy process, and it is by no means a short process. Landing on the islands may actually provide the hikers with the chance to "get closer to nature" and develop an attitude of admiration towards nature.
Thinfor's proposal also aptly balances the interests between hikers and us nature conservatists. The hikers may enjoy their hikes in autumn or winter when less terns breed.
