The family Ardeidae includes 72 recognized species of long-legged, long-necked birds known as herons, egrets, and bitterns. The genera Botaurus and Ixobrychus are referred to as bitterns, and the monotypic genus Zebrilus contains the zigzag heron or bittern, forming a distinct group within the Ardeidae family. Egrets, which are mainly white or have decorative plumes during breeding season, are not biologically distinct from herons. Herons have evolved long beaks as an adaptive trait.