The breeding habits of Siberian cranes, the third-rarest crane species and possibly the most seriously threatened, seem to be influenced by light. The light increases will continue weekly by one hour until the light reaches the 22-23 hours of daylight found in the cranes' arctic breeding grounds during their breeding season. The increase in light is believed to stimulate the birds' reproductive organs, hopefully resulting in a clutch of two eggs by mid-May.
Siberian cranes are extremely difficult to breed in captivity.
The Zoo did breed its two pairs of Siberian cranes prior to 1999, but the crane eggs were infertile, probably because the zoo was not yet utilizing the lighting system, and the male's reproductive organs weren't stimulated. India is in the southernmost wintering range of the central population of Siberian crane. India intends to use the birds as a teaching tool. The cranes would be on display at a government-run conservation center as part of an education program developed to help local Indian people identify the bird and be aware of it's highly endangered status. There are only about 4 birds left in the flock that winters in India at the Keoladeo Ghana National Park.