First it was the hawklet adopted by bald eagles. Then it was the lioness nursing the leopard cub. And now in the latest example of interspecies care, there’s video of a cardinal feeding goldfish.

Originally posted on YouTube in 2010, the footage shows the red bird hopping alongside a goldfish pond, then dropping what appears to be seeds into their waiting mouths.

According to the caption with the video, the cardinal would come back to the pond as many as six times a day to feed the fish. (Explore National Geographic's backyard bird identifier.)

Why would a bird feed an entirely different species? Princeton biologist Christina Riehl has a few ideas.

“My best guess is that