Sub-order 4. Columbae.—Pigeons. Nidicolous. Vomer vestigial. With large crop, vestigial caeca. Columbidae, cosmopolitan, since Miocene. Dididae, flightless, recently extinct. Didus, dodo, Mauritius. Pezophaps, solitaire, Rodriguez.
12. Order Cuculiformes.—Desmognathous, nidicolous; zygodactylous, or with the outer toe reversible.
Sub-order 1. Cuculi.—Cuckoos. Quinto-cubital. Cuculidae, cosmopolitan. Musophagidae, plantain-eaters and touracos, Ethiopian since Miocene.
Sub-order 2. Psittaci.—Parrots. Zygodactylous; aquinto-cubital. Cosmopolitan, chiefly tropical. Trichoglossidae, lories, Austro-Malayan. Nestor, New Zealand. Cyclopsittacus, Eos, Lorius, &c. Psittacidae, tongue smooth, incl. Stringops.
13. Order Coraciiformes.—Nidicolous. Nares imperviae, holorhinal. Downs restricted to the apteria or absent. Thirteen to fifteen cervical vertebrae. Mostly desmognathous. Deep plantar tendons connected with each other.
Sub-order 1. Coraciae.—Either (1) with long spina externa sterni, Coraciidae, rollers, Old World. Momotidae, neotropical, motmots and todies. Alcedinidae, kingfishers, cosmopolitan or (2) with long spina communis. Meropidae, bee-eaters, Old World. Upupidae, Upupinae, hoopoes: palaearctic and palaeotropical. Bucerotinae, hornbills, palaeotropical; Irrisorinae, woodhoopoes, Ethiopian.
Sub-order 2. Striges.—Owls. Outer toe reversible. Schizognathous. Long caeca. Flexor tendons normal. Hypotarsus simple. Cosmopolitan.
Sub-order. 3. Caprimulgi.—Nightjars. Nocturnal. With gaping mouth. Ten remiges and ten rectrices. Spinae sterni vestigial. Caeca functional. Steatornithidae, Steatornis, oil-bird or guacharo, South America. Podargidae, Australasian, Caprimulgidae, cosmopolitan.
Sub-order 4. Cypseli.—Tenth terminal remex the longest. With short spinae sterni. Without caeca. Cypselidae, swifts, cosmopolitan. Trochilidae, humming-birds, American.
Sub-order 5. Colii.—Mouse-birds. First and fourth toes reversible. Ethiopian.