A female king penguin in the UK's only breeding colony for the species is a male.
A female king penguin was mistaken for a male
The true gender of Magnus, who was formerly known as Maggie, was uncovered after eight years when staff at Birdland Park and Gardens in Gloucestershire saw the bird attempt to start mating with another male penguin.
Keepers sent the penguin's feathers for DNA testing where it was revealed that Magnus was actually a male.
The 10-year-old penguin was bred in Denmark and arrived at the wildlife park in 2016 with staff under the impression that the creature was a female.
A spokesman for Birdland said: "Magnus seemed to settle in well, even catching the attention of fellow penguin Frank.
"But when keepers observed 'Maggie' attempting to mate with Frank, suspicions grew. A feather sample was sent for DNA testing, and the truth was revealed: Magnus is definitely male."