Male terns catch fish for their female partner as a part of courtship and bonding. When the female accepts the offering, they usually mate shortly afterwards.
For me there is nothing common about the common tern. I think it’s a very elegant and streamlined bird with a fascinating way of courting.
The first photo shows a male flying by, on his way to hunt for fish for his female partner.
Female forming a nesting pit in the shell island. Or maybe this is all a part of the courtship and bonding between male and female, who knows?
Male shouting to other species in the air to prevent them from landing in its territory.