Raptors are an indicator species of biodiversity because they are at the top of the food chain. The decrease of biodiversity also puts the raptor species in danger. Regular raptor counts provide very important information about the population status as well as being an important indicator of biodiversity.
Istanbul is one of the most concentrated places (bottleneck) in the world of raptor migration between Africa and Eurasia. More than 95% of the world population of the Lesser Spotted Eagle and tens of thousands of raptors such as the endangered Egyptian Vulture migrate through Istanbul. Due to this intense bird migration, both sides of the Bosphorus are located within the Bosphorus Key Biodiversity Area.