I don’t know a lot about Terns. My first encounter with a Tern is when I was walking on a beach and some bird with a black head dived bombed me, it did not hit me but it kept diving at me. I walked away and that ceased.
Now I know this Tern had a nest nearby and it was self defence.
There is several types of Terns and I don’t know if they all migrate, but the Arctic Tern does, it goes from the North Pole to the South Pole and back every year. I don’t know if I have seen the Arctic Tern or not.
However, in New Zealand, we have the Fairy Tern, the common Tern, the Caspian Tern and the Caspian Tern has a large head. That is as much as I know.