Swifts start to share their secrets


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.

Common Swift carrying geolocator (BTO).

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.

Journey of one tagged Common Swift (BTO).

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.

Part of this article is taken from the BTO members' magazine, BTO News.

Written by: BTO