Two miles off the Llŷn peninsula in Wales lies Bardsey Island, an exposed, rocky landmass 1.5 miles long and just over 0.5 miles at its widest point. Bardsey mountain rises over almost half of the island, with a height of 167 metres and rare lichen species found at the top. It’s only reachable by boat and has just 12 properties, one being Bardsey Bird and Field Observatory – my home for the week. I’m here for a university birders week, and on a clear, mild and slightly windy night – a relief given how strong the wind can get here – we head out into the darkness to look for a rarely seen and fascinating species. As we walk along the gravel track, our gaze is fixed on the incredible night sky. There is so little light pollution here that the island was recently designated as Europe’s first dark sky sanctuary. Even the Milky Way is visible with the naked eye. Dark silhouettes glide overhead, sounding like squeaky dog toys. As we wander towards a grassy stone wall, I see a black and white medium-sized bird sitting on the top. Then another, and another. These are Manx shearwaters, a seabird of the open ocean. Nearly 30,000 of these birds call Bardsey home, nesting in burrows and thriving due to the lack of ground predators. We are helping with a long-term scheme to ring and monitor these birds. Steve Stansfield, director of operations at the observatory, explains how to put on a metal ring, each with a unique number to help us to track and identify each individual. In autumn they will migrate to the South Atlantic, mostly off Brazil and Argentina, with the last juveniles leaving in late September or early October; they’ll arrive back here in late March next year. A Manx shearwater that nested on the island in 2008 was shown by its ring to be over 50 years old, and would have flown around 5m miles in its lifetime. These ones are adults; at night-time they like to sit on and around the walls near to their burrows. During the day, when we ring the juveniles, we have to put our hands down the burrows and carefully take them out. As I carefully attach the ring with Steve’s help, I think about all the phenomenal landscapes it has seen. Placing it back where it was found, I wish it good luck. Who knows – it might just make it to 50. Mya Bambrick’s trip was part of her charity fundraising project 21 Wildlife Walks, raising money for the British Trust for Ornithology