For a long time breeding Bearded Vultures in captivity seemed almost impossible. Before the first successful reproductions at the Alpenzoo Insbruck it was only in the twenties that a pair at Sofia Zoo had successfully raised chicks. One of the main problems was the difficulty in distnguishing male and female Bearded Vultures by external features. This hampered the formation of pairs. Because in the case when two males are put together, these behave like a pair, but, obviously, they produce no eggs. Today by using new technical sex determination has become much easier. Within the project all young Bearded Vultures are raised exclusively by parent birds. Raising by human " foster parents " would lead to irreversible behavioural deficiencies.