Tracking Manx Shearwaters on their 20,000 kilometres round trip

January 2009. Using miniature geolocators, 12 Manx Shearwaters were tracked for the first time on their migration. These small (400g) seabirds, related to albatrosses, undertake an extraordinary trans-equatorial, trans-Atlantic migration from their breeding colonies around Britain.

The study showed that their migration path follows the oceanic winds, revealing their overwintering destinations and the long-distance movements of females during their pre-laying exodus. Using machine learning techniques, the study uncovered previously unobserved marine stopover behaviour. Such ocean wandering species remain poorly understood, despite their role as harvesters of marine ecosystems on a global scale and their potential as indicators of ocean health.

UK and conservation relevance
Most of the world's population of Manx Shearwaters breeds on islands around the UK, where they dig underground burrow nests and live a completely nocturnal life. The UK therefore has a special responsibility for the species' protection. Whilst good protection on land is provided by the conservation status of several island colonies such as Skomer (where this study was conducted), Skokholm, Lundy, Bardsey and Copeland, their life at sea is much of mystery, and protection of important resource areas is currently minimal.

Stop over behaviour
The study used geolocators to study the migratory patterns of the birds on their 20,000 kms round trip to the Patagonian shelf off Argentina every year, showing a remarkable and little recognised stop-over behaviour on route. In a parallel study published last year, Shearwaters were tracked on their foraging excursions using GPS, discovering that Skomer birds depend predominantly on areas of the Irish Sea north and west of Pembrokeshire.

‘Spatial ecology'
A long term aim of the project, in collaboration with scientists at Microsoft Research in Cambridge, is to understand the species' spatial ecology using an automated sensor network to measure individual activity in relation to environmental factors both at the nest and at sea. It is hoped that the novel system will have wide applicability in the future for studying the needs of vulnerable species, with minimal human disturbance.