Newsletter / Blog
2012-06-30 Amazing Common Swift Migration – BTO geolocators tell all.
A third of
British Swifts have been lost since 1995, but the reasons underpinning this
decline are unclear. BTO scientists are involved in a project aiming to address
these knowledge gaps. Tiny geolocators were fitted to adult Swifts captured at
the nest in summer 2010 and retrieved in summer 2011 when these birds returned
to breed. The results of this work are revealing the migration routes and
important wintering areas for this species, which could help to identify key
areas for Swift conservation.
The first results
show how incredible these small birds' annual journeys are. We now know that
the wintering range of individual Swifts is huge, with birds visiting several
countries across Africa once they've completed
their post-breeding season migration. Swifts also live up to their name, with
one individual taking only 5 days to travel 5,000 km from West Africa back to
the UK.
Interestingly, this bird stopped for 10 days in Liberia before embarking on this
leg of its return journey, indicating the location of a previously unknown
stopover site for refuelling, where conservation efforts could now start to be
focused.
Chris Hewson, who
has been analysing the British data, is already amazed by the conservation
value of the new maps. "The ten-day stopover in West Africa is really
interesting, because presumably the birds are fattening ready for their journey
back to Britain — we know
they can make it back from there in less than a week! Previously it was thought
that, because they feed on the wing, Swifts simply make their way more slowly,
but directly, feeding as they go, without the need for extended stopovers. This
is completely new information and pinpoints a focal area for future research.
As the Swift hasn't advanced its arrival date in Britain, understanding the species'
spring migration strategy will be a very important step." It is difficult
to provide confident estimates of the size of the decline in Swift numbers but
everyone agrees that numbers are going down. The only difference that we, as
individuals, can make is to ensure that there are nest-sites available. However,
looking at the year-round story of one Swift's life, there may well be other
processes at play that we need to understand.
The Swift
geolocator project has only been possible thanks to excellent collaborations
between BTO staff and volunteer ringers. The Swifts tagged so far have been
caught at study colonies operated by Paul Noakes (Great Yarmouth), Doug Radford
(Fowlmere) and Jamie Hooper (La Société Guernesiaise, Guernsey). We hope to
continue this work in 2012 and would be pleased to hear from ringers or
non-ringers alike who study suitable colonies — colonies in nestboxes and particularly those with cameras in
the boxes are especially suitable.
We would also be
very pleased to receive the remains of eggs found underneath Swift boxes, both
those found early and late in the season. It is not uncommon for lost eggs to
be found under boxes and we would greatly appreciate receiving remains found,
so that isotopic analyses can be undertaken. If you can help, please contact chris.hewson@bto.org.
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