Vandals who targeted a RSPB nature reserve in Lincolnshire could damage future plans for the site, it has been claimed.
Display boards have been damaged and fires started inside the main 360-degree hide at Frampton Marsh near Boston.
Managers said that if attacks persisted, facilities and activities may have to be limited.
Police confirmed they were investigating a series of incidents.
Site Manager John Badley said: "We want to put things on here at the nature reserve that people will come and enjoy.
"But there is a danger that if this keeps happening we will have to scale back some of the events and facilities we want to put in at the reserve."