Where on Earth do British House Martins go?


The British Trust for Ornithology (BTO) hopes to answer one of British ornithology's greatest mysteries using the very latest that technology has to offer in a project starting this summer. The House Martin is well known to many people; from April to September it lives cheek by jowl with those lucky enough to have this energetic little bird nest under their eaves. In recent years, however, the number breeding here in the UK has fallen by two thirds, leading to the species being Amber-listed as a bird of conservation concern and in need of help.

House Martin
House Martin collecting mud — a classic, yet increasingly infrequent, summer scene (Photo: B Callow)

Though we know a lot about the breeding ecology of the House Martin in the UK, once September arrives and this enigmatic bird heads off south for the winter it virtually disappears from our radar. It is not known where in Africa House Martins winter, or how precisely they get there. If ornithologists are to start understanding what is driving the decline of the martins, then it is these questions that will need to be answered.

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This summer, the BTO aims to use the latest technology to discover the routes that House Martins take to Africa and to find out exactly where they spend the winter months. BTO researchers plan to do this by fitting a tiny (shirt button-sized) device known as a geolocator to each bird. Weighing less than a gramme, the device contains a clock, a calendar and a light sensor, together with enough memory to store all of the data collected from the day it is fitted until the day it is retrieved.

By comparing daylight length, as measured by the light sensor, with the time and date recorded, scientists at the BTO are able to determine where on the planet the device was at any given time. This information will then reveal the wintering areas, together with the location of possible stopover and refuelling sites, precise migration routes and the timing of the migration through Europe and Africa.

Paul Stancliffe of the BTO commented, "I have long dreamed of being able to follow a bird like the House Martin on its migration from Britain to Africa, to get a glimpse of the places it is passing through and the places that it chooses to stay and rest for a while before continuing on its journey. It is very exciting to think that we are on the brink of new discoveries that should help these delightful birds and provide them with a more optimistic future. This technology comes at a price and we need help to secure enough of them to make the project worthwhile. Anyone interested in seeing how they might be able to help can find out more by visiting www.bto.org. Each device costs £170 and we hope to be able to fit them to at least 20 birds. We need help to support the scientists developing this project."

For more information please visit http://www.bto.org/volunteer-surveys/house-martin-survey/movements.

Written by: BTO