Ed Gernon adopted a German shepherd mix that was so feral, it "fought other dogs and killed cats."
Rex was dangerous, Gernon said, after having lived on the streets and hunted for his own food.
And so the California man was stunned when Rex came upon a wounded hummingbird and stood rooted to the ground.
"He suddenly stopped and he would not move," Gernon told KCBS-TV. "I mean it's tiny and it's dead as far as I'm concerned. It's covered in ants. It's got no feathers."
Gernon took the teeny-tiny bird inside and began feeding it from a tiny vial full of sugar water. Hummer, as Gernon calls the bird, eats every 15 minutes from dawn to dusk.
He says he taught the creature to fly again by buffeting the bird with a hair dryer.
"It was this creature. This fragile creature that the whole world wanted to kill and he was trying to protect her, so I thought I'd go the distance," Gernon said.
All three have been happily living in Gernon's home for more than a year. Hummer uses Rex's water bowl as a bath tub and a drinking fountain. Hummer alights on Gernon's finger and receives human kisses.
Gernon says he has been leaving his doors and windows open of late because it's mating season for hummingbirds. But Hummer shows no interest in moving out.
"I rescue this dog. He rescues the bird. The bird rescues all of us in a weird sense and it's just a miracle," he said.