bongorob says it's the third time they've nested this year and he still doesn't know if they've reared any chicks. If they haven't, maybe this is the reason?
The pigeons successfully reared a chick in 2010, when the nest was in exactly the same place.
It only takes one idiot to make a notice like this necessary. I'm afraid it's an inevitable consequence of the increasing number of visitors that there will also be an increasing number of idiots at the zoo. Although most of the visitors are sensible and well-behaved of course.
