It stops flying only as its life comes to an end.

Flying (This creature can't be blocked except by creatures with flying or reach.)
This creature can block only creatures with flying.

Welkin Tern

The List

Sailors have come to regard them as bad luck, for they falsely bring hope of land.

"It preys on other birds. And drakelings. And drakes. Pretty much anything that crosses its flight path is fair game."
—Amira, skycaptain of Thune

"The sky hedrons are covered with tern nests. It's as though the birds have given up on the land altogether."
—Ilori, merfolk falconer