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Swift by nature

23 May 2014 | Posted in Birds ,

Author Ian Hepburn

Head of Conservation

swift / Stefan Johansson swift / Stefan Johansson

Swifts are amazing. I feel my heart and soul lift when the first of these masters of the skies appear in late spring. The sight and sound of them stops me in my tracks. It's that unmistakable scream. They scream loud and long and with attitude and in little gangs, often referred to as 'screaming flights' or 'screaming parties'. One second the sky is empty, still and quiet. The next moment it's an explosion of noise, the source of the sound moving around fast, wheeling and diving, sometimes coming so dangerously close you feel the breeze of their speed brush your face.

My soft spot for this, my favourite of all British birds, goes back to childhood experience. As one of a bunch of kids out of school, wandering around, turning over stones and poking at unfortunate creatures to watch their reactions, we found a grounded swift on a gravel track near a high chain-link fence between a sports field and an allotment in suburban London. A first close encounter with nature well, with anything much bigger than a worm or a snail. In turn we eagerly, gently held the bird, unsure quite what to do but taking full advantage of the chance to feel the incredible softness of its body feathers contrasting with the harsh stiffness of its long, curved wings. Noticing its soft, black, feeble legs and tiny sharp claws, we tried to guess what might be wrong with it. I can't recall what happened to the bird: it probably ended up being handed over to a parent to 'make it better'. But that experience had a profound effect on my interest in nature and helped set me on course for a lifetime fascination with birds and birding.

So back to the aerial antics of the common swift. Just how quick are they?

I was pretty sure they'd be among the fastest birds, but I didn't appreciate that recent studies place them at number one! The fastest level flight (so excluding the gravity-assisted power-dive of a peregrine) was recorded by scientists at Lund University investigating the aerodynamics of swifts. They found, in the high-speed low-altitude 'screaming parties', a maximum level flight speed of 31.1 metres per second (that's 70mph), averaging 20.9 m/s (47mph).

Other recent studies have started to unravelled the life of 'British' swifts during the nine months of the year that they spend on migration to and from and within their southern African wintering areas. Evidence from recoveries of swifts ringed in the UK showed the wintering grounds to be a swathe of sub-Saharan Africa from the Congo Basin to the Indian Ocean. But thanks to 'A320' - a swift tagged with a tiny geolocator in Cambridgeshire in late July 2010 - we now know more about the pattern and duration of movements within the wintering grounds. This will be vital information for conservation action. While it's incredibly difficult to determine changes in the breeding population of swifts, all the indications are of a decline. Quite how much that can be attributed to changes in breeding conditions as, for example, traditional nesting sites in older buildings are lost, and how much might be the result of changes in their wintering areas we just don't know. But it seems sensible to give our declining population of swifts a boost by adding artificial nest boxes to buildings wherever possible.

Comments

  • jan honeysett:

    24 May 2014 15:49:03

    i live in Mottingham se london and for the passed 4 years i have been monitoring the arrival of the amazing swifts they seem to be nesting in the eves of the 1950 houses that boarder a recreation field near my flat,they have been arriving the same time each year always between 14th/18th May,what wonderful creatures they are !!

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