The shock for zoo officials came this Sunday, when a gamekeeper went to the birds’ enclosure to check on the winged ones and found two Great Indian Horn Owls missing. An endangered specie, the city zoo had seven such owls, also called the ‘Eagle Owl’, found primarily in rocky and arid areas.

Senior zoo officials said they found the cage locks intact and the birds could have flown away due to carelessness by one of their workers. The authorities, though, are not ruling out theft.

The birds’ enclosure in Delhi Zoo is located in an isolated place where a horseshoe-shaped building is divided into 30-odd cages by strong walls. The opening is covered with iron mesh, which stop birds from taking wings. “We have lost two of our birds,” a zoo official, who did not want to be named, confirmed on Tuesday. “A search is on.”

The official said zoo authorities have since sent a letter to Nizamuddin police and informed them about the incident.

According to the official, the gamekeeper who normally looks after the birds was on leave due to an illness when the incident occurred; a new man had replaced him. The stand-in gamekeeper’s inexperience, coupled with negligence while handling the cages, could have led to the incident, the official said.

Nikhil Devasar of ‘Delhi Birds’, a network of bird-watchers, said besides the city zoo this particular species of owls can only be found in Asola Bhatti Wildlife Sanctuary near Vasant Vihar. “They have really strong wings that enable them to fly at great speed,” Devasar said. “I would not be surprised if they are at Asola sanctuary even as we talk.”

Devasar dismissed the idea that the birds could be in danger, for they “make great predators” and thus would be able to “survive in the open”.

Zoo director D N Singh was not available for comments.

Delhi Zoo has 50 species of birds. While thousands of migratory birds flock the zoo’s waterbeds during winter months, the owls, parrots and peafowl provide amusement to visitors during the summer season.