Manx shearwaters surveyed for first time in 20 years
A British seabird known for its daredevil flying stunts is being monitored for the first time in 20 years on a remote Welsh island.
Manx shearwaters, who fly so low that their wingtips almost touch the water, have been counted on Middleholm Island off the Pembrokeshire coast in South Wales by National Trust rangers and volunteer researchers from the Wildlife Trust of South and West Wales (WTSWW).
The monitoring team employed an unusual method to count Manx shearwaters, playing audio recordings of their call into their burrows and then listening out for a response.
Together with neighbouring Skomer and Skokholm, Pembrokeshire's islands are home to the world's largest breeding colonies of the Manx shearwater, with approximately 50 per cent of the global population living there.
Monitoring the Manx shearwater colony is essential for assessing population health and measuring the effects of external factors on population numbers, such as climate change.
James Roden, National Trust area ranger for North Pembrokeshire says: “For this year's census we played the male and female calls of the Manx shearwater down individual burrows on an audio device. If a bird responded to the call then we recorded the burrow as active.
“This technique is used as the birds are in their burrows during the daytime, and usually fly at night.”
The medium sized black and white birds are well adapted for life at sea with long, narrow wings, and small feet tucked far back on their bodies.
Although they breed on Pembrokeshire's islands, the Manx shearwaters spend their winter months 7,000 miles south, off the coast of Argentina in the south Atlantic – with some birds completing the journey home in less than a fortnight. They nest in burrows as they cannot walk easily, and they move clumsily, which makes them easy prey.
The surveying was conducted by James and a team of five WTSWW volunteer researchers over one eight-hour day. The work was an incredibly sensitive operation as Middleholm Island isn't usually open to the public, and there are no paths, and no easy access to the island.
“We hope that by carrying out this census in partnership with WTSWW we will find that the Manx shearwater population is stable or has increased, matching the trend we have seen on the neighbouring islands of Skomer and Skokholm.
“With many seabird colonies around the UK in real trouble, it is critical that these surveys are carried out,” James concluded.
With a large amount of data to collate, the results are expected to be released this winter.