In Kardzhali, in the center of the town, there is a unique heron colony located in old correction of the Arda Riverbed. The heron colony on the Arda River is unique in Bulgaria because it is the only colony of herons nesting so close to people. Little egrets, night and squacco herons, little bittern and pygmy cormorant are among the species. All are protected under the Biological Diversity Act, and the little cormorant is among the globally endangered species. Poaching many of the species is a criminal offence.