Thanks for all the responses. To clarify, I was not in any way suggesting that what I was seeing is unusual. Pizzey’s book mentions it. Most responses are from
coastal SE Australia, so I am still not sure how widespread the habit is. I think that the strangest one is that Sandra mentioned
roosting high in dead trees at the Mugga Lane tip. I go there often (both the tip and along
road). Maybe I’m guilty of watching the road whilst driving, (lots of kangaroos there). That is even stranger than at coastal venues. I was more angling at obtaining hints on the context for why these birds should do that. It is not as though they are Sea-Eagles
looking for an opportunity to swoop down on a fish. It is not that they are getting away from other pelicans, as they even have 3 pelicans perched on 3 lights on one pole. They clearly like to do this and it has some benefit, as it is a high energy behaviour.
I notice most of the venues reported are beachside communities with lots of passing, walking, running, etc humans. For now the best explanation I can offer is maybe the reason is as simple as when perched up there, they are immune from being bothered and having
to walk, fly or swim away from passing people, dogs, or whatever. And they can stay there unbothered until they decide to come down. That will be my theory for now. When on the ground they sure do “appear” to act indignant at having to get out of the way.
I wonder can there be any other benefit?