Birds seem to fly with such apparent ease that it is hard to comprehend the mechanics behind their aerial acrobatics.
Seemingly specially built for flight, their special hollow-like bones are dense but are strong and stiff and support the bird as they lift off the ground in flight. A birds wings are shaped like an aerofoil, much like an aeroplane's wings, which lowers the pressure above the wing, generating lift.
Hummingbirds are the acrobats of the bird family, and can hover in mid-air, flap their wings over 50 times a second and purposefully fly backwards! Their hovering ability is challenged by that of the kestrel, which can suspend them selves over grass verges, keeping their head perfectly still in order to spot scuttling mice and voles below.
Most fast-flying birds use powered, flapping flight, however this expends a great amount of energy. Peregrine falcons get round this when they reach speeds of 320 kilometres per hour, the fastest speed of any animal, with their stooping dives.
Soaring birds, such as eagles and vultures, glide between warm thermal uplifts and spiral within to gain height. This strategy is fantastic for these larger birds who would need to exert a lot of energy to power their flight.
Take-off can be the one of the most challenging aspects of flight for larger birds. This can be tackled in multiple ways. Some take a run-up in order to generate enough airflow, others simply face into the wind or drop off into the air from a tree branch or cliff edge.
Although we associate birds with flight, some don't fly at all. This is mainly down to a lifestyle that doesn't require flight. Ostriches are excellent runners, reaching speeds of 72 kilometres per hour, and penguins are built to swim, although it could be argued that they almost fly through the water.