Largest order of birds

The largest taxonomic order of birds is Passeriformes, more commonly known as the perching birds or sparrow-like birds. Of worldwide distribution, it contains 6,595 species across 143 families, according to the 2024 Cornell Lab's Birds of the World Checklist. This equates to approximately 60% of all bird species, the total number of bird species currently numbering 11,017.

Passeriformes also contains the largest taxonomic family of birds, Tyrannidae (the tyrant flycatchers), which number 441 species, according to the 2024 Birds of the World Checklist. All of this family's species are exclusive to the New World, and represent 4% of all bird species.

Certain bird groups, by virtue of their specific size, behaviour and/or localities, tend to yield disproportionate numbers of new species. Hummingbirds, for instance, often yield hitherto-undiscovered species, on account of their tiny body size coupled with their frequently remote, inaccessible mountainous habitats, enabling them to be readily overlooked or never even reached by ornithologists. Similarly, new species of small owl still come to light quite regularly, having hitherto remained undetected by scientists due to their diminutive size, nocturnal lifestyle and existence on small, often remote, rarely visited islands.