Plate 1. The family Picathartidae consists of two very unusual species: (A) the Yellow-headed Picathartes from west Africa, and (B) the Grey-necked Picathartes, restricted to Cameroon and Gabon. (A, Willie de Vries; B, Markus Lilje)

Plate 2. Giant Haast’s Eagle attacking moas. The ancestral moa flew from Gondwana to New Zealand before undergoing an adaptive radiation that produced at least nine flightless species. (John Megahan)

Plate 3. The Grey Tinamou is a flying palaeognath that inhabits Amazonia. Tinamous lie deeply within the flightless ratite ‘tree of life’, a finding that disproved the continental drift theory for palaeognath biogeography. (Lars Petersson)

Plate 4. Fossil hunting on Vega Island, Antarctica, during the austral summer of 2016: (A) base camp on the shoreline of Vega Island; (B) the expedition’s helicopter was a new and welcome addition to the scientists’ toolkit; (C) palaeontologists scouring the frozen ground for Cretaceous fossils. (Jin Meng)

Plate 5. Vegavis iaai fossil (left) and computerised tomographic (CT) scan of same rock concretion (right). This Magpie Goose-like Cretaceous bird was discovered on Vega Island, western Antarctica, in 1992. At least five modern bird lineages diverged before the K–Pg boundary, based on the inferred placement of Vegavis: palaeognaths, chickens, screamers, the Magpie Goose and ducks. (Julia Clarke)

Plate 6. Vegavis flying above a mid-sized dinosaur amid a Nothofagus forest on the shoreline of Vega Island, Antarctica. The discovery of its fossilised syrinx suggests that the avian voice box originated after modern birds diverged from dinosaurs. (Nicole Fuller)

Plate 7. The flightless Chubut Steamer Duck of Patagonia evolved 15,000 years ago, as the result of glacial melting and rising sea levels. (John Reilly)

Plate 8. (A) The Coscoroba Swan and (B) the Cape Barren Goose diverged from the rest of the Anserinae around 23.5 million years ago in the southern hemisphere, and well before the swan–goose split in the northern hemisphere. (John Reilly)

Plate 9. Lucy Hawkes, a physiological ecologist at the University of Exeter, fitted several Bar-headed Geese in Mongolia with devices to monitor their altitude, wingbeat frequency and heart rates. The birds were caught during the brief period of wing moult when they couldn’t fly. (Lucy Hawkes)

Plate 10. The 42.5-centimetre-long everted phallus of the Lake Duck is not only longer than the duck itself but also longer than the penis of any other species of bird. (Kevin McCracken)

Plate 11. The prehistoric-looking Hoatzin reached South America by crossing the Atlantic Ocean on floating vegetation. (Lars Petersson)

Plate 12. Reconstruction of the 61.6 million-year-old penguin Waimanu manningeri that lived along the east coast of South Island, New Zealand, soon after the K–Pg extinction event. Waimanu was already flightless, like all modern penguins. It swam, loon-like, on the surface using its feet, and dived using its modified wings for locomotion. (Chris Gaskin, Geology Museum, University of Otago)

Plate 13. The King Penguin (illustrated), like the larger Emperor Penguin, belongs to the genus Aptenodytes, a lineage that is basal to all other living penguins. The ‘great penguins’, as they are collectively known, evolved from an ancestor that lived 40 million years ago. (John Reilly)

Plate 14. An Emperor Penguin huddle or ‘turtle’ during the Antarctic winter. Periodic shuffling ensures that each penguin takes its turn at the centre of the huddle: a remarkable adaptive strategy to conserve heat. (Stefan Christmann)

Plate 15. Luis Monteiro (1962–1999), a Portuguese scientist whose field and laboratory investigations led to the discovery of the sympatric speciation of storm petrels. (Robert Furness)

Plate 16. (A) Monteiro’s Storm Petrel off the Azores: the brownness of the bird’s feathering, created by bleaching, suggests a hot-season breeder. (B) Monteiro’s Storm Petrel on Praia islet. Remarkably, these birds may use the same nest burrows as the Band-rumped Storm Petrel, which breeds in the cool season. (A, Peter Alfrey; B, Nuno Oliveira, Portuguese Society for the Study of Birds – SPEA)

Plate 17. The Bar-tailed Godwit is a record holder among migrating birds: a staggering non-stop journey of 11,500 kilometres from Alaska to New Zealand that lasts nine days. (Shaun Templeton, Elm Wildlife Tours)

Plate 18. An adult Oilbird at its roost in Humboldt’s Cave, Venezuela. The Oilbird possesses the highest evolutionary distinctiveness (ED) score of any bird and has not shared its genes with any other taxa for over 70 million years. (Walter Jetz)

Plate 19. The coevolution of plant and hummingbird has led to some remarkable morphological adaptations. (A) The Buff-tailed Sicklebill has a bill that arcs a full 90 degrees downwards to enable it to reach nectar from Centropogon flowers; (B) the Sword-billed Hummingbird possesses a beak longer than its body and can obtain nectar from the elongated corollas of passion flowers. (A, Christopher C. Witt; B, Rolf Nussbaumer)

Plate 20. The Kakapo, the world’s most genetically isolated parrot, is the only surviving member of the genus Strigops. (Dylan van Winkel)

Plate 21. Skin of the extinct Stephens Island Wren sold to the Liverpool Museum by the ornithologist and collector Henry Baker Tristram. The flightless basal passerine may have had the smallest natural range of any known bird. (National Museums Liverpool, John Reilly)

Plate 22. The enigmatic Sapayoa split from the broadbills 50 million years ago and crossed Beringia to reach Central America. (Petra Rank)

Plate 23. Superb Lyrebirds, most noted for their excellent mimicry, are basal songbirds restricted to southeast Australia. (Ian Montgomery)

Plate 24. Extended phenotypes. (A) The maypole bower of male Vogelkop Bowerbird, with his decorations. (B) A male Satin Bowerbird holds a cicada case in his bill and displays to a female who has entered his ‘avenue’ bower. (Tim Laman)

Plate 25. A Hawaiian Crow will carefully choose and shape a stick to snag its prey. (Minden Pictures)

Plate 26. (A) The Wilson’s Bird-of-Paradise and (B) the Magnificent Bird-of-Paradise evolved by vicariance after geological forces split their ancestral population. (Tim Laman)

Plate 27. Two adult male Emperor Birds-of-Paradise displaying to a nearby female. The species evolved after becoming isolated in the Huon Peninsula. (Lars Petersson)

Plate 28. Sexual selection underpins the absurd ornamental head-wires and bouncing displays of the male King Saxony Bird-of-Paradise. (Tim Laman)

Plate 29. The extraordinary loud and powerful vocalisations of the male Trumpet Manucode are the result of an extremely long trachea: one that has six concentric loops between the skin and breast muscles. Females lack a coiled trachea, indicating that the male’s windpipe has evolved as the result of millions of years of sexual selection. (Katrina van Grouw, The Unfeathered Bird, 2012)

Plate 30. Four types of melanosome are responsible for the structural colours of African starlings: an evolutionary development that underpinned the clade’s rapid speciation. (A) Greater Blue-eared Starling; (B) Superb Starling. (Lars Petersson)

Plate 31. The evolution and speciation of the Common Blackbird involved two sweepstake dispersals across the Atlantic Ocean. (Andreas Trepte)

Plate 32. (A) The Italian Sparrow arose 8,000 years ago as the result of hybridisation between (B) the House Sparrow and (C) the Spanish Sparrow. (A, alamy.com; B, Peter Garrity; C, Steve Mills)

Plate 33. Study of Zebra Finches has contributed to our understanding of the genetics and evolution of birdsong. (pixabay.com)

Plate 34. The Louisiade White-eye, like other insular white-eyes, exhibits behavioural or psychological flightlessness. (Lars Petersson)

Plate 35. Cassia Crossbill, a species that has coevolved for the past 6,000 years with the Rocky Mountain Lodgepole Pine. (A) A close-up of a male’s beak; (B) a female employs her beak to prise open a Lodgepole Pine cone. (Craig Benkman)

Plate 36. The diversification of beak morphology facilitated the speciation of Darwin’s finches by allowing a greater range of food resources. The insectivorous Grey Warbler-Finch (A) has a small pointed beak; the Common Cactus Finch (B) has a large pointed beak for medium-sized seeds, while the Large Ground Finch (C) has a large blunt beak for large seeds. (B, Rosemary Grant)

Plate 37. The Masked Flowerpiercer from South America has evolved a long, hooked bill and a grooved tongue for extracting nectar from flowers. (Lars Petersson)