Not quite as sinister as you may suspect. I believe this is because this is a bird sanctuary, and any kind of non-avian flying object may disrupt the normal environment in which the birds live. I know from personal experience with slope soaring along the coast in the SF area that many types of birds object to RC gliders and will even attack them. My gliders have been attacked by pelicans, gulls, terns and other coastal birds. Just the way the law requires humans to stay away from sea turtles in Hawaii and not hunt fish in many protected areas.