They may not be the biggest, but the Manx Shearwater is a bird built for epic adventures across entire oceans. Here’s all you need to know about these two-tone glide masters, which were once mistaken for island dwelling trolls…
Manx Shearwaters are supreme marine explorers, spending most of the lives gliding over vast oceans. The small black and white seabirds use their long straight wings to skim just above the surface of the sea, a bit like little albatrosses. The two species are related, both sharing an odd arrangement of nostrils that gives them the name ‘tubenoses’. They use their epic flying skills and special noses to find food such as herrings, sardines and sprats.
In late winter and early spring, around 80% of the world’s Manx Shearwater return to the UK to breed. They’re a sociable bunch, nesting in around 50 colonies on steep grassy slopes on offshore islands mainly along the west coast. They choose these isolated spots so they’re away from predators such as rats.
Once back at the nest site, the adult birds reunite with their lifelong mate and find an underground burrow to lay a single egg.
Being a small bird, going to and from the burrow with food for their chick is a risky business, with larger seabirds often ready to divebomb. But the Manx Shearwater is shrewd and waits for darkness to fall before returning with food.
On still nights, the birds’ eerie cackles and calls shatter the darkness, as their mate guides them home. In days gone by Norse sailors were spooked by the calls and thought the Scottish island of Rum was inhabited by trolls.
In good conditions, Manx Shearwaters are great providers, and the one chick is so well fed that they grow to nearly double their parents’ weight. They often put on so much weight they have to slim down a bit before they’re ready to make their maiden flight.
Once they’re ready, usually in July, the chicks fledge under the cover of darkness. They soon set off on the first of their epic migrations to the coast of South America, a distance of 6,000 miles. Manx Shearwater are one of the longest-lived UK birds, with one recorded living to 55. This means some individuals travel over five million miles in their lifetime – the equivalent of flying to the moon and back roughly 10 times.
Sadly, all is not plain sailing for these nifty navigators. They’re on the Amber List of UK Conservation Concern, which means that they’re moderately at risk.
One of the biggest threats is to their nest sites. Manx Shearwaters have evolved to nest underground, keeping their precious egg away from predators. But these burrows don’t protect them from rats, which are sometimes accidentally introduced to islands, with devastating consequences.
With most Manx Shearwaters nesting in the UK, we’ve a big role to play in securing their future by protecting these vulnerable colonies and making sure boats don’t accidentally bring rats and other invasive species to our seabird islands.
But for a bird that spends nine months of the year gliding over entire oceans, we also need protection that works across man-made borders. Only then can we protect these heroic explorers’ food sources and migratory pathways.
In Wales, the RSPB nature reserve Ramsey Island is a key breeding site for many seabirds including Manx Shearwater. In the past accidentally introduced brown rats had decimated the island's bird populations, but work by the RSPB means the island is now free of rats and mice and seabird populations are recovering. To keep the island’s birds safe, there are now strict bio-security procedures in place.
Elsewhere, the RSPB is working with partners to protect seabirds on the Isle of Scilly. Here breeding seabird numbers had been falling for 25 years, but after freeing the islands of St Agnes and Gugh from rats, the birds are beginning to recover. In 2014, the first Manx Shearwater chicks were recorded on the island in living memory and numbers have been steadily increasing.
The fact that Manx Shearwaters nest in remote places and only come to their burrows in the dark makes them pretty hard to spot. But adult birds do travel many miles in the search for food and if you’re lucky you can spot foraging adults all along the coastlines of the UK during the summer months.
