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The swift is a most extraordinary bird, which hardly ever lands, spending almost its entire life in the air! This medium-sized bird is even believed to sleep while in the air and can spend up to ten months without stepping foot on solid ground. The swift is from a family of highly aerial birds known as Apodidae. It is not closely related to any passerine perching species. Closer to the hummingbird; both swifts and hummingbirds are unusual in that they have short legs and very small feet, making them awkward on the ground. Scientists say if you see a swift on the ground for any length of time, it's likely to be injured and may need help. The only time a swift spends time out of the air is when it is nesting and rearing young, but even then, you're very lucky to spot this fascinating species because it doesn't build a nest in the traditional way. Instead, swifts nest in holes, often in old buildings, or in specially-made swift nesting boxes that are designed to be attached high in the eaves of a house. If you see swifts flying fast and low around buildings, shrieking loudly, they are likely to have a nest up there. You will never see them perching on fences or telephone wires, as their small feet make walking and perching almost impossible.   What does a swift look like? The average swift is around 17cm long and weighs between 36g and 50g. With a wingspan of up to 48cm, its feathers are dark brown, although they can look black against the sky. A contrasting pale throat, long wings and a short, forked tail give it a distinct silhouette.   How fast does a swift fly? The common swift can cruise at a maximum speed of 70 mph, or 112 km per hour. Taking into account the amount of time it spends in the air; it is estimated to cover around 200,000 km in an average year! Swifts arrive back in the UK in May, after spending winter in warmer climates, like the Congo around West Africa and across the Sahara. In good weather, they can fly non-stop from Morocco to British shores. This is an amazing flight of extreme endurance, as they can cover the last leg (1,600 miles) in just two days.   Where do swifts live? Their natural habitat includes farmland, urban and suburban areas, grassland and wetland. After their long journey, especially in wet weather, they can often be seen swooping around over ponds, reservoirs and flooded gravel pits, feeding in the air on flying insects. On fine days, swifts are usually seen flying higher overhead, still catching insects while in flight. They are around on UK shores until the end of September, according to the RSPB, when they start their winter migration again.   What do swifts eat? Their diet consists of many kinds of flying insect such as mosquitoes, aphids, flying ants, beetles and hoverflies. They need to catch huge numbers every day to replenish their energy, due to the amount of flying they do. Most of their feeding is done at a height of around 50 metres up to 100 metres. In turbulent weather, the insects are swept higher into the air. Opportunist feeders, Swifts have been known to follow swarms as high as 1,000 metres. They drink by catching raindrops in the air, but they will also fly low over water and skim a mouthful of water from the surface as they swoop down.   How do swifts sleep in the air? Extensive studies have been carried out to enable scientists to better understand how swifts can even sleep in the air. Research was carried out by scientists from the Department of Biology at Lund University, in Sweden, who used micro data-loggers to study the common swift. The loggers record the birds' location once a month and their activity every five minutes. Researchers have concluded the birds live in the air for months at a time, landing only to breed. All other activities are carried out in the air. Spending up to three months at a time in the air, dictated by their breeding patterns; the pallid swift lays two clutches of eggs per breeding season. The common swift lays only one clutch of eggs a year, spending as long as ten months in the air. The most amazing find from the data-loggers was the flight pattern of the swifts. When they reached a particularly high altitude, they would start gliding and appeared to actually sleep for short periods while in the air.   Is the swift a threatened species? Sadly, swift numbers are in decline. There are believed to be 59,000 breeding pairs in the UK at present. A protected species in the UK and in the European Community, it is illegal to kill or harm them, to take their eggs or damage their nests. They do no harm and makes little or no mess. As they are almost continually in the air, they leave no piles of droppings under trees or on buildings. One reason for their decline is because they nest almost completely in older buildings - most of them dating from pre-World War II. Scientists estimate that none of the buildings constructed in the 21st century are suitable for nesting swifts because building materials and techniques have changed and modern buildings don't allow access to birds. The greatest loss of swifts occurred between 1995 and 2016 when more than 50% of the UK's swift population disappeared. Scientists say the amount of National Lottery funding to refurbish historic buildings during this period has had a direct result on nesting swifts. Also, there has been a refurbishment programme of social housing since 1997, with widespread demolition of old buildings, leading to a further loss of nesting sites. The new replacement buildings usually exclude birds. Finally, the use of insecticides has hastened the decline of the swift. Crops such as oil-seed rape are often sprayed more than 20 times as they grow. As a result, insect populations are declining. Some studies suggest the UK has lost 80% of its insect population in recent years, and as swifts rely on flying insects to survive, many are sadly starving to death.   How can we help swifts? The government has asked local authorities to maintain the biodiversity of their area to help the swift population. In London, the Borough of Camden has recognised the swift as a "flagship species" for the urban environment and has pledged to take action to stop its further decline. Measures are also being taken by local authorities in Aylesbury, West Sussex, Amsterdam, Basel and Zurich to maintain the swift population. Householders are urged to lobby their local authority to ask what they are doing to help the swift. People can also help by making a place where swifts can nest, such as a DIY or commercially-made special nesting box to attach to their house. They can be installed into new and old buildings without harming the structure. This will help save the beautiful swift from possible extinction in the future. This is the ideal time of year to go outdoors to spot swifts. If you're bird-watching this spring and want to encourage swifts to nest around your home, check with charities such as the RPSB, or Swift Conservation, to find out more about nesting boxes. They are amazing birds – let’s help them to survive!