Ground-dwelling birds survived the end-Cretaceous mass extinction
Life on Earth has been punctuated by a number of catastrophic mass extinctions throughout history. During these events, diverse taxonomic groups collapsed from the relatively rapid and widespread extinction of large numbers of species. Precipitated by a massive asteroid impact on Earth that occurred more than 65 million years ago, the end-Cretaceous mass extinction led to the obliteration of forests around the world and caused the disappearance of approximately three-fourths of all plant and animal life on Earth. Most notably, all nonavian dinosaurs went extinct at that time. Included in that extinction event were many species of prehistoric birds (avians), which are considered by taxonomists to be members of the dinosaur family. Larger avian species that were dependent on trees for nesting or food comprised the majority of extinctions. However, smaller ancestral forms of ground-dwelling birds survived. See also: Aves; Chicxulub impact crater; Cretaceous; Dinosauria; Extinction; Extinction (paleontology); Forest; Mass extinctions; Tree