30 Days Wild | Day 20

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The day started with a proverbial bang in the morning, when a message came through on the VH radio that an Ocean Sunfish was lolling about in the sea just off Pen Cristin. I’d just returned from a morning walk, so sprinted up the hill to join Mark and Sian, before locking on to this bizarre creature with my binoculars. I’ve never seen a sunfish, even though they are relatively frequent in British waters, so I was pretty elated to watch one – finally!

Sunfish, or Mola mola, are the World’s heaviest known bony fish (known as ‘Osteichthyes’), and females can reputedly produce some 300 million eggs at a time – more than any other vertebrate. They are mysterious creatures, subsisting primarily on a diet of jellyfish and spending most of their time at depth (>200m) in the ocean. Their periodic appearance at the sea surface is thought to serve several functions: one is to bask in the sun’s insolation as a means of ‘thermal recharging’ (hence the english name ‘Sunfish’), whilst the other is to receive a sort of parasite cleansing from birds like gulls picking off unwanted hitch-hikers from it’s body. Its scientific name is derived from the Latin mola for ‘millstone’, which its grey and circular shape closely resembles.

Fascinating animals!

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the sunfish with two curious Herring Gulls wondering what on earth it is!
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the South End in the morning sun

The conditions during the day were dominated by a fresh north-easterly wind that persisted until the day’s end; by evening there was not a breath of wind, and the temperature rocketed to 20’C under a hazy vista of high cloud.

I spent much of the morning preparing three more tags to deploy on Manx Shearwaters as part of my tracking study into their foraging behaviour. This also entailed finding the perfect burrows with incubating birds inside on which to deploy these tags. Finding the ‘right’ burrow can be tricky! Some of the shearwater’s burrows can be several feet long, and so well out of arm’s reach to attain the bird within; others possess awkward dog-legged turns and jagged obstructions that make it difficult to weave your arm inside; others still contain birds that weren’t even sat on their egg: inexperienced young pairs who haven’t quite got the idea of ‘incubating’ yet!

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a Shearwater ready to receive it’s special backpack GPS unit

After finding the appropriate study burrows, Steve Stansfield came down to attach the tags onto the birds, with the help of last year’s assistant warden Steffan Walton and his partner Becky – visiting from Sandwich Bay Bird Observatory for a week or so!

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The tag fitted neatly to the shearwater’s mantle feathers

A prominent feature of today was the continued movement and arrival of migrant insects…Red Admirals were all over the island, some flying straight in off the sea, whilst others making good use of nectar sources in the island’s gardens; a male Black-tailed Skimmer on Pen Cristin was just the second ever record for Bardsey, whilst two immigrant Red-veined Darters – a scarce species here – were seen too. We also recorded Diamondback Moths and Silver Ys during the day, which are similarly migrant species benefitting from the high pressure system sat over the nearby continent.

The afternoon was spent around the East Side, clambering about Bae Felin’s boulder field in search of auk chicks to ring…we managed to fit BTO rings to some 40 Razorbills and 10 Guillemots, whilst hundreds wheeled with heavy wingbeats overhead. The boulderfield – white-washed with bird guano – also held a handful of gull chicks, and some sweet-smelling clefts in which Storm Petrels were no doubt nesting.

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A Razorbill chick
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Bae Felin: one of the island’s biggest Razorbill colonies

Whilst around in the seabird colonies, we conducted more breeding bird counts of chicks, eggs, nests and adults, whilst also taking pictures of ringed adult auks for re-trapping sightings. All very much valuable data to contribute to the long-term study of the island’s seabird populations, which are currently facing mixed pictures.

Some close-ups of the Razorbill’s rings. It’s really handy to photography the legs and read out the unique alpha-numerical code later on. The right hand bird below is almost as old as me, being ringed in 1998 on Bardsey! Probably in the same colony too…

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