Instruct: Given a question, retrieve documents that answer the question.
Query: Can all birds fly?
Flightless birds are birds that through evolution lost the ability to fly.[1] There are over 60 extant species[2] including the well known ratites (ostrich, emu, cassowary, rhea and kiwi) and penguins. The smallest flightless bird is the Inaccessible Island rail (length 12.5cm, 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, 156kg). Ostriches are farmed for their decorative feathers, meat and their skins, which are used to make leather.
All tinamous are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general, they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.
Many birds migrate in flocks. For larger birds, it is assumed that flying in flocks reduces energy costs. The V formation is often supposed to boost the efficiency and range of flying birds, particularly over long migratory routes. All the birds except the first fly in the upwash from one of the wingtip vortices of the bird ahead. The upwash assists each bird in supporting its own weight in flight, in the same way a glider can climb or maintain height indefinitely in rising air. Geese flying in a V formation save energy by flying in the updraft of the wingtip vortex generated by the previous animal in the formation. Thus, the birds flying behind do not need to work as hard to achieve lift. Studies show that birds in a V formation place themselves roughly at the optimum distance predicted by simple aerodynamic theory. Geese in a V-formation may conserve 12–20% of the energy they would need to fly alone. Red knots and dunlins were found in radar studies to fly 5 km per hour faster in flocks than when they were flying alone. The birds flying at the tips and at the front are rotated in a timely cyclical fashion to spread flight fatigue equally among the flock members. The formation also makes communication easier and allows the birds to maintain visual contact with each other.
This is a monotypic species. All tinamou are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general, they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.
All tinamou are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general, they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.
All tinamou are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general, they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.
All tinamou are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general, they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.
What can be said is that "Foro", with its stocky body and rather weak flight apparatus was in all likelihood a bird that did not fly vast distances. Consequently, it is not very likely that it is congeneric with "Hoatzi", as North and South America were still separate by some of shallow seas and the Central American island arc when these birds lived, and seem to have shared only strong-flying and highly migratory genera such as seabirds. Being able to fly at all would still enable even a rather sedentary bird lineage to spread across all of the Americas by then of course; "Foro" and "Hoatzi" seem to be distinct genera, but nonetheless in some way related and possibly quite closely so.
This is a monotypic species. All tinamou are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general, they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.
This is a monotypic species. All tinamou are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general, they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.
All tinamou are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general, they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.
Default logic can express facts like “by default, something is true”; by contrast, standard logic can only express that something is true or that something is false. This is a problem because reasoning often involves facts that are true in the majority of cases but not always. A classical example is: “birds typically fly”. This rule can be expressed in standard logic either by “all birds fly”, which is inconsistent with the fact that penguins do not fly, or by “all birds that are not penguins and not ostriches and ... fly”, which requires all exceptions to the rule to be specified. Default logic aims at formalizing inference rules like this one without explicitly mentioning all their exceptions.
All tinamou are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.
All tinamou are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general, they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.
This is a monotypic species. All tinamou are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general, they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.
The V formation possibly improves the efficiency of flying birds, particularly over long migratory routes. All the birds except the first fly in the upwash from one of the wingtip vortices of the bird ahead. The upwash assists each bird in supporting its own weight in flight, in the same way a glider can climb or maintain height indefinitely in rising air. According to a 1970 paper, in a V formation of 25 members, each bird can achieve a reduction of induced drag and as a result increase their range by 71%. The birds flying at the tips and at the front are rotated in a timely cyclical fashion to spread flight fatigue equally among the flock members. Canada geese, ducks and swans commonly form a skein in V formation.
All tinamou are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general, they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.
All tinamou are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general, they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.
All tinamou are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general, they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.
A version also exists in India, Pakistan, Germany, Slovakia and Hungary where an analogy to what can fly and what cannot is emphasized instead of Simon saying or not, i.e. "Chidiya ud" (Hindi) which translates to "Bird fly" or "Alle Vögel fliegen hoch" (German) which is "All birds fly high". The term 'bird' can then be replaced with a thing that cannot fly. These games are usually played more with gestures than actual jumping.
All tinamou are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general, they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.
All tinamou are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general, they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.
This is a monotypic species. All tinamou are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general, they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.
All tinamou are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general, they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.
This is a monotypic species. All Tinamou are from the family Tinamidae, and in the larger scheme are also ratites. Unlike other ratites, tinamous can fly, although in general, they are not strong fliers. All ratites evolved from prehistoric flying birds, and tinamous are the closest living relative of these birds.