Evolution of birds

group of related bird species in the Galápagos Islands

dinosaurs possessing feathers

evolution, adaptation, and origin of birds

derivation of birds from a dinosaur precursor, and the adaptive radiation of bird species

thumb|250px|Hypothetical restoration of "one of the Pro-Aves", as shown at the British Museum by William Plane Pycraft in 1906 (here extracted from Pycraft 1910 book A History of Birds). Proavis is a hypothetical extinct species or hypothetical extinct taxon. The term was coined in the early 20th century in an attempt to support and explain the hypothetical evolutionary steps and anatomical adaptations leading from non-avian theropod dinosaurs to birds. The term has also been used by defenders of the thecodontian origin of birds.