Old World quail in the context of "Pternistis"

Galliformes /ˌɡælɪˈfɔːrmiːz/, also known as gallinaceous birds or landfowl, is an order of heavy-bodied terrestrial birds that contains about 290 species. The order is divided into five families: Phasianidae (chicken and junglefowls, Old World quails, partridges, pheasants, turkeys, peafowl and grouse), Odontophoridae (New World quails), Numididae (guinea fowl), Cracidae (including chachalacas and curassows), and Megapodiidae (incubator birds like malleefowl and brushturkeys). Galliformes and the semi-aquatic order Anseriformes (waterfowl) are collectively called fowl.

Galliform birds have adapted to most environments except innermost deserts and perpetually icy regions, inhabiting every continent except Antarctica. They are important in their ecosystems as seed dispersers and insectivores/vermivores, and many are skilled ground-dwellers that escape predators by running rather than flying. They are sexually dimorphic, and males of most species are more colorful than the females, with often elaborate courtship behaviors that include strutting, fluffing of tail or head feathers, and vocal sounds. They are mainly non-migratory.

The New World quail are small birds, that despite their similar appearance and habits to the Old World quail, belong to a different family known as the Odontophoridae. In contrast, the Old World quail are in the Phasianidae family, sharing only a remote phylogenetic connection with their New World counterparts through their mutual classification within the Phasianoidea superfamily. The geographical range of the New World quail extends from Canada to southern Brazil, and two species, the California quail and the bobwhite quail, have been successfully introduced to New Zealand. The stone partridge and Nahan's partridge, both found in Africa, seem to belong to the family. Species are found across a variety of habitats from tropical rainforest to deserts, although a few species are capable of surviving at very low temperatures. There are 34 species divided into 10 genera.

The legs of most New World quails are short but powerful, with some species having very thick legs for digging. They lack the spurs of many Old World galliformes. Although they are capable of short bursts of strong flight, New World quails prefer to walk, and run from danger (or hide), taking off explosively only as a last resort. Plumage varies from dull to spectacular, and many species have ornamental crests or plumes on their heads. Moderate sexual dichromism is seen in plumage, with males having brighter plumage.

Phasianidae is a family of heavy, ground-living birds, which includes pheasants, grouse, partridges, junglefowl, chickens, turkeys, Old World quail, and peafowl. The family includes many of the most popular gamebirds. The family includes 185 species divided into 54 genera. It was formerly broken up into two subfamilies, the Phasianinae and the Perdicinae. However, this treatment is now known to be paraphyletic and polyphyletic, respectively, and more recent evidence supports breaking it up into two subfamilies: Rollulinae and Phasianinae, with the latter containing multiple tribes within two clades. The New World quail (Odontophoridae) and guineafowl (Numididae) were formerly sometimes included in this family, but are now typically placed in families of their own; conversely, grouse and turkeys, formerly often treated as distinct families (Tetraonidae and Meleagrididae, respectively), are now known to be deeply nested within Phasianidae, so they are now included in the present family.

Quail is a collective name for several genera of mid-sized birds generally placed in the order Galliformes. The collective noun for a group of quail is a flock, covey, or bevy.

Old World quail are placed in the family Phasianidae, and New World quail are placed in the family Odontophoridae. The species of buttonquail are named for their superficial resemblance to quail, and form the family Turnicidae in the order Charadriiformes. The king quail, an Old World quail, often is sold in the pet trade, and within this trade is commonly, though mistakenly, referred to as a "button quail". Many of the common larger species are farm-raised for table food or egg consumption, and are hunted on game farms or in the wild, where they may be released to supplement the wild population, or extend into areas outside their natural range. In 2007, 40 million quail were produced in the United States.

The Phasianinae (Horsfield, 1821) are a subfamily under the family Phasianidae of the order Galliformes. This subfamily notably includes the true pheasants, tragopans, tetraonids, Coturnicini, Pavonini, amongst other members.

Although this placement was once considered monophyletic and separate from the partridges, francolins and Old World quail (now-defunct Perdicinae) until the early 1990s, molecular phylogenies have shown that this subfamily is paraphyletic. For instance, certain genera like Lophophorus and Meleagris, as well as members of the genus Perdix, are cladistically more closely related to grouse and true pheasants, whereas other genera like Tetraogallus, Coturnix, and members in the genus Alectoris, share a much closer kinship to peafowl and junglefowl. There are two clades in this subfamily: the erectile clade and the non-erectile clade, referring to erectile tissue in the bare, non-feathered parts of the face. Both clades are believed to have diverged during the early Oligocene, about 30 million years ago.

Perdicinae is a polyphyletic former subfamily of birds in the pheasant family, Phasianidae, regrouping the partridges, Old World quails, and francolins. Although this subfamily was considered monophyletic and separated from the pheasants, tragopans, junglefowls, and peafowls (Phasianinae) till the early 1990s, molecular phylogenies have shown that these two subfamilies actually constitute only one lineage. For example, some partridges (Perdix genus) are more closely affiliated to pheasants, whereas Old World quails and partridges from the Alectoris genus are closer to junglefowls. Due to this, the subfamily Perdicinae is no longer recognized by the International Ornithological Congress, with the species being split among 3 subfamilies.

Perdicinae is a non-migratory Old World group. These are medium-sized birds, and are native to Europe, Asia, Africa, and the Middle East. They are ground-nesting seed-eaters. The subfamily includes the partridges, the snowcocks, the francolins, the spurfowl and the Old World quail.