The swift is one of the least understood and most mysterious birds. Though in shape it may look like the common swallow or the housemartin, there is no evolutionary or familial connection. It has closer links with the hummingbird. Astonishingly, ornithologists have identified a hundred different sub-species of the swift in four distinct tribes. The swift spends most of its life in the air where it feeds on flying insects, mates and sleeps - yes sleeps! - only returning to earth to make little nests of grasses and leaves which are attached to high rockfaces or the facades of old buildings with saliva. If you look at a swift's feet you will see that they are short, thin and stubby - designed for nesting times and nothing else. In flight, these feet are tucked nicely out of way like an aeroplane's undercarriage. The birds routinely fly to 10,000ft at night-time, around 4,000ft higher than previously thought. Swifts are also able to navigate through different wind speeds while sleeping, automatically adjusting their flight to stay on a specific course. Approximately 80,000 pairs of swifts migrate to Britain each summer, although numbers have been declining partly because modern buildings offer fewer opportunities for nest sites. The birds migrate more than 4,000 miles from Africa to England in late April. Typically, the swift will fly at 70mph but can achieve speeds of over 100mph, making it one of the fastest fliers in the animal kingdom. In flight, the average common swift will cover an estimated 125,000 miles a year. For all these reasons, surely the swift deserves our admiration and our protection too.