Compared with most of our spring migrant birds, swifts arrive late – around early May – and leave early – around late July.
Although their stay is brief, their list of charms is lengthy.
In towns and cities, long summer days are electrified by stunning flypasts of these screaming (yes, that is the noise that they make) dynamos.
Their exhilarating calls form an essential part of urban summer soundscapes – accompanying the chatter of people in beer gardens and the sizzle of sausages on barbeques.
And then there is their aerial prowess.
There is a certain raw exuberance about swifts, like gifted young athletes who haven’t yet learnt to play their sport with fear.
Swifts flit above, within and between our streets with remarkable agility; their movements made all the more exciting by their mysterious dark appearances, which give the impression of flying silhouettes.
Such is their mastery of the air that swifts rarely come into land.
Remarkably, youngsters that fledge the nest this summer might not touch down again until 2015 or 2016, when they too will attempt to raise a family.
Until then, they will live on the wing – eating airborne invertebrates and drinking by catching raindrops or by skimming surface water. They will even sleep and mate in mid-air.
Being so averse to landing makes the journeys that are taken by swifts difficult for scientists to follow.
If a chick that is ringed in the UK survives for a few years, the most probable place that it will be recaptured is back in the UK when it returns to nest – its travels in between remaining a mystery.
Ascertaining where swifts go in the interim period is important; not least because these iconic birds are in decline.
In less than 20 years, a third of British swifts have been lost.
Several reasons might account for this, including a drop in the number of cavities in which they nest.
But what happens in Britain is only part of the picture.
To discover where swifts go after they leave our shores, the BTO is involved in a project in which swifts are adorned with tiny ‘geolocators’.
A flavour of the journeys that they undertake has already emerged.
One adult swift was tagged at the nest in summer 2010 and was recaptured on the same breeding grounds in 2011. Its tag was recovered and the data were downloaded.
Upon leaving the UK in summer 2010, the individual passed through France and Spain, taking two weeks to arrive at its wintering areas above the Congolian rainforests.
It then traversed great swathes of Africa during our autumn and winter.
Important feeding sites for this bird en route also became apparent – areas in which it loitered for periods before moving on.
One such location, in the skies over Liberia, provided vital fuel for this bird before it embarked upon its epic 5,000 mile journey from West Africa back to the UK in May 2011.
Which, incidentally, it did in a cool five days.
Swifts are a vibrant part of our urban summers and they need our help.
One thing that you can do is to share your sightings of swifts through surveys that are coordinated by the BTO.
How to spot a swift
Observers might confuse swifts with swallows or house martins, but swifts are larger and are all-dark in appearance, save for a small whitish throat patch (swallows and house martins are pale all over the breast and belly, and swallows also have a red face).
The profile of these birds in flight also differs. Swifts have narrow, scythe-shaped wings while those of swallow and house martin are broader.
Swifts also lack the tail streamers of swallows.
If in doubt, wait for the bird to make a sound. Nothing else screams like a swift.
The British Trust of Ornithology (BTO) works in partnership with over 40,000 volunteer birdwatchers to chart the fortunes of UK birds.