sentences:  It includes 400 bird species from 21 orders, 63 families and 198 genera.The varied natural habitat, relief and climate and relatively untouched environment are among the main reasons for the many bird species in the country.The numerous islands and wetlands along the Danube including the Persina Natural Park and Srebarna Nature Reserve, as well as the lakes and swamps along the Bulgarian Black Sea Coast, support many species of diving and aquatic birds such as ducks, swans, pelicans, grebes, spoonbills and many others.