Monday, 14 May 2018

Manxies moving in?

Manx shearwaters (manxies) may not be as well known as the popular puffins but on a global scale they are probably the most important species on Skomer. They are a true seabird, distantly related to the albatross and only come to land to breed, where they nest in underground burrows. They have evolved to spend their lives out on the ocean with their legs positioned far back on their bodies, perfect for diving and swimming. They find it difficult to walk on land and shuffle ungainly around on their bellies. For this reason they only breed successfully on islands free from land predators such as rats, stoats and cats. Even here they are extremely vulnerable to predation by gulls. They are therefore far more elusive than puffins and only come to land to access their burrows under cover of darkness.

This year we will be completing a full island Manx shearwater census, last undertaken in 2011. Staff and specially recruited volunteers will be working hard throughout June to gather this data. Given that at the last census there were over 316,000 pairs this will be a major undertaking. This figure represents just under 50% of the world’s population of Manx shearwaters and therefore Skomer is vitally important to the continued success of the manxie.

Part of the process of protecting the shearwaters requires monitoring and long term survey work has been undertaken by researchers from Oxford University for many years. This has produced vital information regarding their migration routes, foraging strategies and breeding success.
This year we have decided to build and install some artificial nest boxes. This way the birds can be accessed to ring and weigh which is all vital to determining breeding success and adult survival. Our neighbours on Ramsey Island have had success with their nest box colony installed in 2015 and we are keen to see if the same will happen here.

Weighing manx shearwater chicks to monitor their progress

Manx shearwater chick in a nest box on Ramsey Island 2017

Staff and volunteers on Skomer constructed the boxes on the island and they were installed by digging them into the ground which acts as a nesting chamber, curved drain pipe was used to mimic the tunnels. This design has been used successfully for another shearwater species (Hutton’s shearwaters) in New Zealand and Ramsey Island copied this design for their Manx shearwater boxes.

Drainpipe mimics burrow tunnel

Nestbox and tunnel entrance

The whole Skomer team got involved digging in boxes

The boxes have been dug into an area close to the warden’s house in North Haven, a naturally dense shearwater colony where we hope that young birds prospecting for a nesting burrow will take a liking to one of the nest boxes. We check these boxes regularly and will keep you informed of how they fare this year. Hopefully if we get any birds in the boxes we will install a camera so that we can monitor how they are doing.

For now we have a camera in an established burrow where a pair of shearwaters have returned to breed. Live pictures from this burrow are being streamed and can be viewed in Lockley Lodge. So if you are visiting Skomer this season, be sure to stop off at the Lodge and see how they are doing.

Manx shearwater in "burrow cam" burrow

Some amazing Manx shearwater facts
  • 90% of the world’s population of Manx shearwaters breed around UK islands. 50% of these breed on the Pembrokeshire islands.
  • Manx shearwaters can live beyond 50 years of age. The oldest known bird was a female that bred on Bardsey Island. She was ringed as an adult in 1957 she was last seen in 2008 and so would have been at least 53 years of age.
  • Manxie pairs separate over winter but return to the same burrow and the same partner every year.
  • Manxies migrate from their breeding grounds around the UK to the Southern hemisphere off the Argentinian coast (8,000 miles) then return to the UK the following year. They may travel up to the equivalent of to the moon and back ten times in their lifetime.
  • Manxies lay only one egg but this is relatively large weighing up to 15% of the adult. After feeding their chick for around 6 weeks the adults leave for Argentina. The chick will emerge from the burrow around a week to ten days later and then leave land to follow a similar route taken by the adults to South America. They won’t touch land until they are two years of age and very often will return to an area very close to the burrow they were reared in.

All these are some of the reasons why Manx shearwaters continue to be one of my favourite birds. I feel privileged to live on Skomer where I only have to step outside my door to hear and see thousands of them coming and going every night.
Anyone wishing to enjoy this experience can do so by booking to stay overnight in our hostel accommodation on Skomer. We are also hosting a “Shearwater week” event form 2nd September to 10th September. This event will include talks by researchers, night walks and chick weighing as part of the experience. Please contact the booking office 01656 724100 for more information.

Sarah J., aka Small Sarah, aka Parmor!
Skomer Visitor Officer

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