The first bird is believed to have appeared on the surface of the Earth approximately 150 million years ago.

Birds are descendants of theropod dinosaurs, and they evolved from a group of small, carnivorous dinosaurs during the Mesozoic Era. The earliest known bird is Archaeopteryx, which lived during the Late Jurassic period around 150 million years ago.

Archaeopteryx had both bird-like and reptilian characteristics. It possessed feathers for flight and had avian features such as wings and a wishbone, but it also retained reptilian traits like teeth, claws on its wings, and a long bony tail. This transitional fossil provides valuable evidence for the evolution of birds from dinosaurs.

Since the appearance of Archaeopteryx, birds have diversified and evolved into the vast array of species we see today. They have adapted to various habitats and developed diverse forms and behaviors over millions of years of evolutionary history.