The proud fathers, known as Z and Vielpunkt, are one of three homosexual penguin pairs at the zoo. They assumed the role of surrogate parents when an egg was cast aside by a heterosexual pair. The zoo has tried to have gay birds incubate an egg before, but this is the only occasion it has worked.
"We are of course, very excited about this," Dr. Joachim Schöne, veterinarian at the zoo, told The Local on Wednesday.
In late April 2009, a female Humboldt penguin laid two eggs. The hetero couple actively nurtured and incubated the first egg, but for unknown reasons, they simply kicked the second egg out of the nest. Zookeepers placed the second-hand egg near the homosexual couple in hopes that both fathers would care for it as their own.
The two penguins, who have been together for more than five years, have proven to be loving parents and evidently happy fathers, said Schöne.
"It's really touching how they both care for the chick," he told news agency DPA.
According to the zoo, such homosexuality is nothing out of the ordinary in the animal kingdom. And since penguins split parenting work evenly, there are no traditional motherly or fatherly roles.
Schöne said the zoo was ecstatic the gay birds decided to take on the trials of fatherhood and they were "absolutely" accepted by the rest of the penguins.
The zoo has maintained a mix of homosexual and heterosexual Humboldt penguin pairs on its grounds for over three years. Zookeepers had tried to encourage the gay birds to breed with some imported females brought in from Sweden in 2006, but they stayed faithful to their homosexual partners.
With breeding in captivity remaining rare, zoo officials are pleased to have parents of any sexual orientation raising baby birds. Four other eggs are excepted to hatch in early June.