BTO: Anxious over swifts’ late arrival

Swift in flight. Picture by Mike Toms/BTO ANL-140905-122331001
Swift in flight. Picture by Mike Toms/BTO ANL-140905-122331001
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Ted Hughes once lyrically described how the returning swifts materialised ‘at the tip of a long scream of needle’, an apt description for these denizens of our summer skies.

From mid-April I begin to cast occasional glances skyward, searching for the scimitar-winged silhouette of an early swift, but it is usually not until the last week of the month that they first appear in any numbers above the town. This year they were late and I felt a certain, unexplained, anxiety; where were they? Why were they late when so many other summer visitors had arrived early? Most likely, they’d been held up by a blocking weather system positioned over southern Europe, temporarily halting their northward migration.

Young swifts in the nest. Picture by John Black/BTO ANL-140905-122342001

Young swifts in the nest. Picture by John Black/BTO ANL-140905-122342001

Swifts spend virtually their entire lives on the wing, touching down briefly on their breeding grounds but otherwise barely connected to the world of us terrestrial creatures. That we claim a sense of ownership over these birds – describing them as ‘our’ swifts – is all the more remarkable because of how little time they spend here. An individual returning to its breeding colony at the start of May will have left again for its southward migration before the end of July.

We know surprisingly little about what swifts do once they have left our shores or, for that matter, where they spend the winter. Up until recently the only information we had was from the small number of swifts, fitted with rings, that had been found in Africa. All this changed in 2011, when a swift known as A320, returned to its breeding colony in Cambridgeshire. This individual had been fitted with a tiny tracking device (known as a geolocator) the previous July by researchers from the Thetford-based British Trust for Ornithology (BTO) and the bird’s return meant that the device could be removed and the information carried downloaded.

The information stored on the device provided our first glimpse of the routes used by British swifts on migration and the sites where they spent the winter. This particular bird had migrated down through France and Spain, skirting Africa’s Atlantic coast before heading east to a wintering area located within the Democratic Republic of Congo. The swift remained here from mid-August until early December, after which it moved south-east to coastal Mozambique. Then, just before the end of January the bird began its northward migration, returning to the Democratic Republic of Congo before moving into West Africa during early April. It was from here that it made the return journey to Britain, a journey of nearly 3,500 miles that took just 10 days.

Of course, this is just one swift among many, and we will learn more as the information from tracking devices on other swifts is revealed. Knowing more about these journeys only adds to my sense of wonder; the annual return of these amazing birds seeming all the more remarkable.

Pictures courtesy Mike Toms and John Black.