Flightless bird

Flightless birds are birds that cannot fly but they can run and/or swim instead of flying, but they did evolve from flying ancestors. There are about 40 species in existence today, the best known being the ratites (ostrich, emu, cassowary, rhea and kiwi) and the penguins. Some birds evolved flightlessness in response to the release from predation, for example on oceanic islands, although this is likely not the case for the ratites as evolutionary origins suggest a continental biogeographical providence.

Two key differences between flying and flightless birds are the smaller wing bones of flightless birds and the absent (or greatly reduced) keel on their breastbone. (The keel anchors muscles needed for wing movement. ) Flightless birds also have more feathers than flying birds.

New Zealand has more species of flightless birds (including the kiwis, several species of penguins, and the takahe) than any other country. One reason is that until the arrival of humans roughly a thousand years ago, there were no large land predators in New Zealand; the main predators of flightless birds were larger birds.

Some flightless varieties of island birds are closely related to flying varieties, implying flight is a significant biological cost.

The smallest flightless bird is the Inaccessible Island Rail (length 12.5 cm, weight 34.7 g). The largest (both heaviest and tallest) flightless bird, which is also the largest living bird, is the ostrich (2.7 m, 156 kg), although some extinct species grew to larger sizes.

Flightless birds are the easiest to take care of in captivity because they do not have to be caged. Ostriches were once farmed for their decorative feathers. Today they are raised for meat and for their skins, which are used to make leather.

There were also other families of flightless birds, such as the now extinct Phorusrhacidae, that evolved to be powerful terrestrial predators.

Many domesticated birds, such as some breeds of domestic chicken and domestic duck, have lost the ability to fly, though their wild ancestors, the red junglefowl and mallard, respectively, are perfectly capable of flight.

List of recent flightless birds
The following are flightless birds from the Holocene epoch. Extinct species are indicated with a dagger (†).

Ratites

 * Ostrich
 * Emu
 * Kangaroo Island Emu †
 * King Island Emu †
 * Cassowaries
 * Moa †
 * Elephant birds †
 * Kiwis
 * Rheas

Anseriformes (Waterfowl)

 * Moa-nalos †
 * Bermuda Island Flightless Duck †
 * Fuegian Steamer Duck
 * Falkland Steamer Duck
 * Chubut Steamer Duck
 * Auckland Teal
 * Campbell Teal
 * Dromornis †
 * Genyornis †
 * Chendytes lawi †
 * Kaua'i Mole Duck †
 * New Zealand geese †

Galliformes (Wildfowl)

 * New Caledonian Giant Scrubfowl †

Podicipediformes (Grebes)

 * Junin Grebe
 * Titicaca Grebe
 * Atitlán Grebe † (reportedly flightless)

Pelecaniformes (Pelicans, Cormorants and allies)

 * Flightless Cormorant

Sphenisciformes (Penguins)

 * Penguins

Coraciiformes (Kingfishers, Hornbills and allies)

 * Saint Helena Hoopoe †

Ciconiiformes (Herons, Ibis)

 * Apteribis †
 * Jamaican Ibis †
 * Leptoptilos robustus †

Gruiformes (Cranes, Rails, and Coots)

 * Cuban Flightless Crane †
 * Red Rail †
 * Rodrigues Rail †
 * Woodford's Rail (most likely flightless)
 * Bar-winged Rail † (probably flightless)
 * Weka
 * New Caledonian Rail
 * Lord Howe Woodhen
 * Calayan Rail
 * New Britain Rail
 * Okinawa Rail
 * Guam Rail
 * Roviana Rail (flightless, or almost (so)
 * Tahiti Rail †
 * Dieffenbach's Rail †
 * Chatham Rail †
 * Wake Island Rail †
 * Snoring Rail
 * Inaccessible Island Rail
 * Laysan Rail †
 * Hawaiian Rail †
 * Kosrae Crake †
 * Ascension Crake †
 * Red-eyed Crake
 * Invisible Rail
 * New Guinea Flightless Rail
 * Lord Howe Swamphen † (probably flightless)
 * North Island Takahe †
 * Takahe
 * Samoan Wood Rail
 * Makira Wood Rail
 * Tristan Moorhen †
 * Gough Island Moorhen
 * Tasmanian Nativehen
 * Giant Coot (adults only; immatures can fly)
 * Adzebills †

Charadriiformes (Gulls, Terns, Auks)

 * Great Auk †
 * Diving Puffin †

Falconiformes (Birds of prey)

 * Terrestrial Caracara †

Psittaciformes (Parrots)

 * Kakapo

Columbiformes (Pigeons, Doves)

 * Dodo †
 * Rodrigues Solitaire †
 * Viti Levu Giant Pigeon †

Caprimulgiformes (Nightjars)

 * New Zealand Owlet-nightjar †

Strigformes (Owls)

 * Cuban Giant Owl †
 * Cretan Owl † (probably flightless)
 * Andros Island Barn Owl †

Passeriformes (Perching Birds)

 * Stephens Island Wren †
 * Long-legged Bunting †