Translated from Dutch NOS TV:
A first in Artis: gay griffon vultures raise young one
Caregivers placed it in the incubator, but then saw how the male couple built a nest on the rock in the vulture compound. It was then decided to put the vulture egg into the nest, where it was then brooded by the males taking turns until it hatched.
Five years ago
Meanwhile, the two fathers take good care of the chick, Artis reports. Five years ago a young griffon vulture was born in the zoo. This year, two chicks were added: the one who was brooded by the gay couple and a chick of two [heterosexual] birds injured in Spain and brought to Artis for convalescence.
Artis is going to investigate whether the two young birds can be freed later into the wild. The zoo participates in the European breeding program for griffon vultures.
This Dutch video says about itself:
This Griffon Vulture with ring number RO4 was ringed in Spain in January 2015 and was seen in the Dennen woodland on Texel [island] on August 1, 2015. On May 20, 2016, this same bird appeared on Texel, at exactly in the same place.