Arcturian

Arcturians were an peaceful bird-like race native to a planet orbiting Arcturus. They were of small stature and possessed wings, claws, and webbed feet. They reproduced by laying eggs.

The Arcturians learned that the density of their world's atmosphere was steadily decreasing, and would be completely gone in a million years. When the air became too thin for flying, they decided to flee in a great fleet of spaceships for a better world. After many thousands of years in space, during which their wings atrophied and they lost much of their technological knowledge, they crossed the forty light years between their world and Earth, upon which they hoped to settle. They discovered the Doctor's TARDIS had materialised in the middle of their fleet and brought it on board their ship, were they told the Second Doctor, Polly Wright and Ben Jackson their history. Knowing that the people of Earth would mistake the Arcturians for invaders and kill them all, the Doctor sent them to the Ninth Dimension so they could find their own home. (PROSE: Only a Matter of Time)