Nature's Greatest Navigators?

Manx shearwaters migrate over 7,000km from Wales to Argentina at the end of every summer but how do the birds know where to go? A study on Skomer Island is trying to nd the answer.

- Jo Price

Every year, more than 18,000 people set an early alarm to spend a day with superstar seabirds at The Wildlife Trusts’ Skomer Island, Pembrokeshire. After a short boat journey on the Dale Princess from Martins Haven – looking out for harbour porpoise while Atlantic puffins whizz overhead – the tourists disembark to start their island adventure.

Visitors take hundreds of photographs and while away the hours watching the frenetic activity of an array of breeding birds on a cliff-face known as The Wick. But what they don’t see, while the sun is out, is arguably Wales’ best-kept secret – hidden beneath the island’s grassy top and only making an appearance after dark.

Joe Wynn’s arm disappears into the earth, as he lies on the ground to conduct a daily check of a study burrow on Skomer. There are 100 burrows marked for research on the island and the doctoral student knows exactly where to place himself to avoid damaging any of them.

He removes a single white egg from the hole and puts it carefully into a container beside research assistant Daryl Mcleod. It is April and the start of the breeding season for this particular feathered resident. “An egg weighs up to 15 per cent of the body weight of an adult, which is kind of nuts really,” he says. “It’s a huge investment, as they only lay one per year, but they do have a high breeding success rate."

Joe’s limb disappears again but this time he removes something much larger, a Manx shearwater or ‘Manxie’. “This one is very chilled – it’s been involved in experiments numerous times,” he says, holding the ringed, adult male. He places it in a bag to weigh it and Daryl jots 485g in a notepad.