Lots of houses have what I only know as chimney grannies. In the cold countries they stop wind coming down the chimney and blowing smoke back into the house. Here they do the opposite job and help vent hot air out of the house in form of natural airconditioning.
Most of them look like this:
However, I spotted this;
I must keep my eyes trained upwards on my travels to see if I can spot any other roof creatures.