There are 10,999 extant species of birds in the world, according to BirdLife International, a global authority on bird conservation.
These birds exist in varying stages of threat, some no threat at all, others said to be on the edge of extinction.
Birds are tough, ancestors of today's birds being survivors of an event that killed most other life on Earth, the fifth mass extinction 65 million years ago.
The previous four date back as far as 400 million years. Huge excess of carbon dioxide was the cause of three of those, a meteor the fourth. All erased life to a large degree.
Scientific observers say we are living in mass extinction number six, in a proposed era called the Anthropocene — Anthropo relating to humans — because we are the source of the trouble this time. Once again, carbon dioxide is the weapon employed.
Dinosaurs and other large animals died in that fifth extinction. Smaller creatures, including unknown bird species, survived. They thrived in a world of reduced threat and competition.
So, today we are one shy of 11,000 species, all descendants of those survivors, shaped and reshaped by natural selection.
BirdLife is the authority for birds when it comes to the annual Red List compiled by the International Union for the Conservation of Nature, which evaluates the status of most plant and animal species worldwide.