Bridges, Stacks and Loomeries

The South Pembroke Coastal Path has to be one of my favourite stretches for a variety of reasons, but in the Spring and early Summer it has a lot to over everyone, spectacular views, great walking, birds, flowers and an enduring mystery to me a variety of geology. But this time I want to concentrate a little on geology and birds. Hidden behind the Castle Martin Tank Range are steep sea cliffs, sea stacks and a natural arch – The Green Bridge of Wales and Elegug Rocks. Arches are created by wave actions on the different types of rock levels within the cliff. Weaker rocks such as shale are protected by stronger and more resilient rocks such a limestone. The constant battering by wave action works away and  breaks through the strong rock and then erodes the weak rock very quickly. But the creative forces that carve out the arch from the living rock are also the very forces that will eventually destroy the arch. In the few years we’ve been visiting the area we’ve been able to witness dramatic changes to the arch. In September 2017 the arch had been untouched in living memory, but the 25th October after being hit by the destructive forces  of Storm Ophelia and Storm Brian a large lump was knocked off the arch.

The Green Bridge a few years ago

Eventually the arch will collapse and leave two stacks similar to the Elegug Rocks about 100 meters east. In the spring and early summer these stacks are ram packed with thousands of nesting sea birds, razorbills, guillemots, fulmars and cormorants. As you approach the cliff edge if the wind is in the right direction, you can smell the birds before you see them. Stack Rocks are named after the guillemots, which in old Welsh were known as elegug.

The Green Bridge this year – notice the missing chance of the side

When I say there were a lot, I mean a lot. Every conceivable legged had a bird nesting, and I’m not sure some of these could even be termed ledges they seemed so narrow. The tightly-packed colonies are known as “loomeries”, and the eggs are laid on the bare rock ledges or ground. The shear mass of birds provides protection for the eggs and chicks from the aggressive Lesser and Greater Blackbacked Gulls which given any opportunity will swoop in and take an unguarded egg or chick. It could be argued that the Guillemot has perhaps the smallest nesting territory of any British bird. It’s been estimated to being only extending a beak length round its nest, about 5cm. 

The Elegug Stacks from the east. The Green Bridge is just around the corner out of shot.

Looking at how shallow the ledges are it is easy to imagine that in these precarious nests the eggs would roll off, but each egg is very pointed, so that if disturbed they roll in a circle rather than fall off the ledge. In the confusion of all these nests how do the parents know they have come back to the right nest? Well, each egg has a unique colour and pattern to help the parents recognize them. Colours include white, green, blue or brown with spots or speckles in black or lilac. This endless variety in colour and pattern associated with their unusual shaped led to a glut of egg collecting, with professional egg collectors abseiling down cliffs to collect the eggs and sell them onto  the open market in an attempt to meet the demand. It must have led to hundreds of thousands of eggs being collected and resulting in the Sea Birds Preservation Act 1869 being enacted within the UK Parliament to restrict the practice and Pete t sea birds during the breeding season. Both parents incubate the egg for 28 to 34 days, swapping in twelve hour shifts.

Walk from Castlemartin to Bosherston

Guillemots have been recorded as travelling distances of 100 km when foraging for their young, but if sufficient food is available closer by, the birds will venture much shorter distances. Ungainly on land, and not the most elegant of fliers, it’s a very different matter when they are hunting in the water. It could be said that Guillemots and Razorbills are the Northern Hemisphere equivalent of flying Penguins. They are surface-divers, foraging for food by swimming underwater using their wings for propulsion. Dives usually last less than one minute

A Guillemot flanked by two Razorbills

What’s in a name? I’ve always know the Guillemot, well as a Guillemot. But it seems that in many other part of the world it’s known as the Common Murre. This name which is used overseas was the Cornish word murre, which was originally noted by Ray in 1678. The Welsh form morr suggests a common Celtic origin. It’s thought that the name Murre is onomatopoetic, from the murmuring noise that the birds make when nesting in their crowded lomery.Having seen a few nesting site now I can believe that. It it also has other local names and I’ve list just a few below. English names for this intriguing bird include Loom and Willock (I like this latter name). Willock is the oldest recorded name having been attested in 1631. This name may be a reflection of the high pitched call of the juvenile bird. In Welsh it’s called Gwylog; Irish a Forach and Gaelic it’s Eun-dubh-an-sgadain. 

A Fulmer flying below us as we stand on the cliff top.

If you get the chance I can recommend sitting in front of a Loomery for a while. There is always something going on. Even if you’re not an enthusiastic bird watcher it will keep you entertained. Aunty certainly wasn’t bored as we sat there on the cliff top having our coffee. Just make sure that the wind is blowing in the right direction, otherwise it can be a bit wiffy!


BirdLife International (2019) Species factsheet: Uria aalge. Downloaded from on 20/07/2019. 

Robinson, R.A. (2005) BirdFacts: profiles of birds occurring in Britain & Ireland. BTO, Thetford (, accessed on 20 July 2019)

Reedman, Ray. Lapwings, Loons and Lousy Jacks: The How and Why of Bird Names . Pelagic Publishing. Kindle Edition. 

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