Bird droppings

if this is at a con, theres policies about that. If they are hanging out on private property, let the property owner know your not happy that someone is taking pictures. See if theres something you can do for them. Talk to them find out about them and what they are doing, the more information you have, the more possibilities are available. If they really are just posting it on a personal blog, it might not be worth worrying about vs the local newspaper.