Notice by a bird hide on a small County Durham (North-east England) nature reserve:
BEWARE DISTURBING BIRDS.
Now some might take this as sound advice to young men at a party, but I think it's a warning to visitors to the nature reserve that if they encounter a bird which is behaving in an odd manner, for example dancing about or advancing in a threatening manner while making a strange and unpleasant sound, especially if the bird is very big - retreat.
I love double meaning signs: from collections I remember "BEWARE OF TRAINS GOING BOTH WAYS AT ONCE" (at a level crossing, also in County Durham) and a sign at a church, "PREACHERS FOR JULY WILL BE NAILED TO THE CHURCH DOOR." I think there's a close connection between picking up this kind of hilarious ambiguity (as opposed to boringly registering only the sensible interpretation) and poetry, and also to being politically subversive and radical (UK meaning not US). Who could take seriously being one of two "Outward-facing Partnership Officers" (Essex County Council)? Lots of people.