Shortly after they hatched at the Zoo Aquarium Madrid, two barn owlets were released into the wild on June 5, marking World Environment Day.
The baby barn owls, the most widely distributed species of owl in the world, are part of a conservation project in cooperation with the Brinzal Nocturnal Raptor Recovery Centre to boost their numbers.
Experts say there are only 37 breeding pairs of owls in the Madrid region.
Veterinarians spent 28 days carrying out basic checks on the newborns, monitoring their weight, analyzing their wings and growth rate and testing their hearing and eyesight.
The two owlets were then transferred to a nest box next to a field. They can be fed on a regular basis without human presence and get to know the surrounding rural area.
Once they are over 50 days old and fully grown, the feeding will be reduced as they slowly learn to fend for themselves.
After two months, the owls will leave the nest box and are expected to adapt to life in the wild. They will be monitored by experts at night.
The zoo said the number of barn owls has fallen in the region in recent decades.
(Edited by Fern Siegel and Judith Isacoff)