Birds of a feather usually flock together—but not in the case of a rare "white" mutant penguin, spotted Monday in a chinstrap penguin colony in Antarctica.
The "blonde" penguin, seen at the edge of one of the South Shetland Islands (map), "astonished" tourists on a National Geographic Journey to Antarctica cruise, naturalist David Stephens, of the Lindblad Expeditions cruise company, wrote on his blog.

Though the penguin looks like an albino, the bird actually appears to have isabellinism, said penguin expert P. Dee Boersma of the University of Washington in Seattle.

The condition is a genetic mutation that dilutes pigment in penguins' feathers, according to a 2009 study on isabellinism published in the journal Marine Ornithology.

This results in a "uniform lightening" of a bird's dark colors, turning the animal a grayish yellow or pale brown, the study said.