Vandals!

On my walk this morning I spent some time watching a bird among the mangroves. I think it was a white faced heron. There are some information boards and recordings of bird calls along the path, so I thought I would check them to confirm my identification. Unfortunately they have been vandalised since I last walked this way.
 
It’s a puzzle. What possible profit or pleasure could anyone gain from doing this?
 
Extra: a very poor photo, but the bird in question can be found among the branches.