Dr. Bridger was nothing more than a chemistry and biology teacher originally, though slowly became detached with his job after discovering the oddities and anomalies of Earth, becoming obsessed and eventually quitting his job to pursue finding secrets.

About when he started to discover the earth humanity was living on was some kind of clone of old earth (which is a nuclear wasteland) he was recruited by a group of scientists dedicated to finding, protecting, and learning about the paranormal, anomalies, and extraterrestrials.
I say protecting because the new-earth government, particularly America, suppresses info on these abnormalities, and will capture and test on anything they find, this is why the rebel organization Bridger works with I so intent on getting to them first.
This same group helps Izzi get on her way out of New-Earth to become an adventurer.

As he spent time within this new group he began to learn about different aliens, magic, and the gods, as you can see he began go devote himself to Aratrice to have further insight into disease medicine, and chemistry, and he kept his brown hair in the form of his feathers! I did not color his Human form hair because I did not see it as important.