There are 7 families of flightless birds in total. They include the Kiwi, Cassowaries, Rheas, Ostriches, Tinamous, Emus and Penguins.

There are also numerous flightless birds within other groups of birds which are mostly made up of species which can fly. Rails, for example, include waterfowl such as moorhens, swamp hens and other small to medium birds which can fly but prefer not to. They cannot fly for any great distance, and within the rail family, there are numerous flightless birds, such as the Takahē and the weka of New Zealand, and the Inaccessible Island rail.

Other bird families have some members which cannot fly, even though most of the family can. The kakapo, which lives in New Zealand, is the world's only flightless parrot. The flightless steamer duck of the Falkland Islands is another bird which is an anomaly with its family. The Giant Coot of South America is unusual, as the adult cannot fly, but the young birds can.

There are many more species of flightless birds. See the related link for a more complete list.

Extinct birds which could not fly include the Moa, dodo, elephant bird and Terror bird.

In one sense, it could be stated that penguins do fly. It's just that they fly underwater, rather than in the air.

There are a number of reasons why penguins do not fly in the air.

Penguins eat fish. The fish they eat swim fairly deep under water, so flying is not an advantage in getting the fish, but swimming is. Therefore, penguins swim rather than fly. Quite simply, they don't fly because they don't need to.

Penguins cannot fly in air because their wings are too small for their body weight. Power required to stay aloft to counteract gravity is proportional to wingspan. Penguins have very small wings, yet are very heavy. The heaviest penguins are heavier than the heaviest flying birds. The heavier bodies of penguins are the result of their special bone structure and the blubber that they carry. The blubber protects penguins from the cold. Cold water can remove heat from the body much faster than air, so a good insulator is required. Colin Pennycuick calculates in his book "Modelling the Flying Bird" that a typical gentoo penguin would need to flap its wings 35 times a second (about equivalent to a hummingbird) to remain aloft. The penguin is simply unable to create enough energy to take off.

If penguins can't fly because they have such small wings, then why do they have small wings in the first place? The answer is that small wings are much more useful underwater because they have lower drag and greater agility. Their wing bones are fused straight, rather than angled like a flying bird's, and this has the effect of making the wing rigid and powerful, like a flipper. The small wings and a streamlined body shape are ideal for diving in water. Larger wings would create too much drag, while the small penguin wings are excellent for high speed swimming.

Unlike the majority of other birds, penguins do not have hollow bones, so are much heavier and harder to support with their small wings. The solid, as opposed to hollow, bones act as ballast to help them dive. Also, being solid, they are less prone to breakage from the stresses of swimming. Some (but not all) flying birds have hollow bones to be lighter.

Penguins also have higher levels of myoglobin and feathers optimized for the aquatic environment. Myoglobin is the main way penguins store oxygen during their long dives. The muscles of flying birds are filled with mitochondria and enzymes to power flight, and there is no space left-over for myoglobin. So, flying birds cannot spend us much time underwater as penguins because they have less myoglobin (less oxygen per body mass) and lower body mass (less over oxygen). Another benefit is that penguins are able to optimize their feathers for the aquatic environment. Penguin feathers are short and tight to keep water away from the skin and to create a smooth surface to lower drag. Flying birds have very different feathers that are fluffy to trap air for insulation.

Owls eat mainly small fury animals or rodents: such as rats, mice, moles, squirrels, bats, etc. They also eat insects and small birds.

Mice, snakes, rabbits, and other small animals.

some owls eat very small insects such as spiders and beetles.

Birds fly in circles for various reasons.

• The birds are simply gliding on thermals, which move in circles.
• The birds are searching for prey
• The birds are performing a mating ritual by flying with each other.

All birds have wings. It's just that some of them are useless for flight.

Even the New Zealand kiwi has wings, though it is often considered to have none. The wings are small and rudimentary, hidden under the kiwis' hairy feathers, but certainly present.

However, some of the flightless birds do not have a tail. The kiwi, for example, has a pygostyle.

• Wagtail
• Warbler
• Waterthrush

• Wattlebird
• Waxwing
• Weaverbird (finch of Africa and Asia)
• Wheatear (small thrush)
• Whimbrel
• Whinchat (small European bird)
• Whippoorwill
• White dove
• Whydah (African songbird)
• Wild turkey
• Willie
• Willow tit
• Wood cock
• Wood duck
• Woodpeckers
• Wood pigeon
• Wren

· Wandering Albatross

· Warbler

· Waved Albatross

· Western Grebe

· Wild Turkey

· Whistling Heron

· White Dove

· White-bellied Heron

· White-bellied Stork

· White-crested Tiger Heron

· White-eared Night Heron

· White-tailed Tropicbird

· Wood Duck

· Woodpecker

· Woolly-necked Stork

· Wren

· Warbler

· Wild Turkey

· White Dove

· Wood Duck

· Woodpecker

· Wren

• Warbler
• Waterthrush
• Wattlebird
• Weaverbird----> finch of Africa and Asia
• Wheatear---->small thrush
• Whimbrel
• Whippoorwill
• White dove
• Whydah --->African songbird
• Wild turkey
• Wren
• woodpecker
• Whinchat -->small European bird

• Wagtail
• Warbler
• Waterthrush
• Wattlebird
• Weaverbird (finch of Africa and Asia)
• Wheatear (small thrush)
• Whimbrel
• Whinchat (small European bird)
• Whippoorwill
• White dove
• Whydah (African songbird)
• Wild turkey
• Wren
• woodpecker