Caspian Terns (Hydroprogne caspia) are a distinctively large tern with an equally large and distinctive red beak.
This group of birds were loafing about near to Swan Bay jetty - a place where I often go to have a look around. The birds were calm, but nervous (if that makes any sense!). I would take a slow step closer, and they would take a few slow steps further away. I suspect it may have been a game.
I tried an indirect approach, where you don't walk directly at the birds, but weave from side to side and move very slowly forward. They just watched and moved backwards as I moved forwards.
In the end I just stood still and waited. And so did they!
In the end the flew off - possibly bored of teasing me and eager to find some food.
These are the best pictures I could manage!