(noun) The scientific, zoological, vertebrate classification of all birds, including modern birds, extinct species and birds in the fossil record. In scientific classifications, Aves is the class that follows the kingdom (Animalia) and phylum (Chordata) under which birds are grouped. The Aves class evolved roughly 150 million years ago, during the Mesozoic Era, from reptiles.
There are roughly 10,000 species of birds in the world today, with dozens of different specialized classifications for bird types, yet all birds share certain characteristics. All birds are warm-blooded vertebrates that lay amniotic eggs. They are typically feathered and have evolved to be specialized for flight; even birds that are flightless today have remnants of flight characteristics in their anatomy and genome. The vast majority of all birds also have lightweight bones and a complex vocalization ability.
Photo – Prothonotary Warbler © Bill Majoros