Ecology, Wales

Cemlyn Bay — Amazing Habitat

A few days ago we visited Anglesey and on our way home we stopped at Cemlyn Bay (it was on our way and there was a little red bird on the map so we thought we’d have a look). The bay has a strange eliptical shingle beach like the Chesil Beach but a perfect curve. At first we thought it was man-made — something to do with the atomic power station on the Eastern promontory but it is natural. There is a brackish lagoon behind this pebble bank.

Walking along the bank we were struck by the unfamiliar plant life — Sea Kale, Sea Campion, Sea Beet and Thrift.

Sea Campion — Seline uniflora (Its leaves are the smaller grey-green ones)
Sea Kale — Crambe maritima with its strange ball like fruits.
Wild Thyme –Thymus polytrichus

At either end there were clumps of sweet smelling purple flowers which I assumed was the sea lavender that the information board boasted, but no, it is Wild Thyme. There was lots of Ragwort and Bird’s-foot Trefoil with many yellow and black striped caterpillars of the Cinnabar Moth.

Cinnabar Caterpillar Tyria jacobaeae

The Cinnebar Moths are protected from predation by absorbing the toxin from the ragwort that makes them foul tasting. When we were children one rarely saw Ragwort as it was zealously sought out and destroyed by farmers as it was known to cause liver failure and death in horses. The toxic alkaloid, Pyrrolizidine, is metabolized by the liver which it gradually destroys — however, nowadays the risk is not thought to be high as the dose needed is great — still, best kept out of pasture and hay.

There were lots of moths as well: Six Spot Burnet Moths, Zygaena filipendulae (not Cinnabar Moths which are similar in colour but a different pattern).

Six Spot Burnet Moth Zygaena filipendulae

Burnet Moth Caterpillars feed on Common Bird’s-foot Trefoil — interestingly this also contains a toxin, a cyanogenic glycoside which when chewed produces cyanide. This also protects them from predation as they are said to release cyanide when attacked.

As we walked around the bay the noise of chattering birds became louder, not gulls, but thousands of terns — clouds of them, swooping and swerving over the lagoon. As we got nearer we could see hundreds perched on rocks and a weir and standing at the edges of the water.

Terns on the lagoon.

Common Terns with red bills, black at the tip, and Arctic Terns with plain red bills. Distinguishing these birds is easier when there are so many, together at close quarters, when one can compare them easily.

Common Tern with young.
Arctic Terns

Sandwich Terns breed here in large numbers (third largest breeding colony in the UK), they are a little bigger with black bills with yellow tips.

Sandwich Terns – juveniles

All the time there were birds flying over us to fish at sea and coming back carrying fish and feeding young.

Sandwich tern -note the shaggy crest.

Walking out onto the headland we heard a strange sound, a mellow moaning, from out on the distant rocks where the surf was breaking,”I wonder…” said Bill raising his telescope, “Yes, Grey Seals!” They were lying like great curved pods, balanced on semi-submerged rocks with heads and tails in the air, waiting for the incoming tide.”

Vivian Hewitt’s House and Walled Lagoon.

On our way back we met the Reserve Warden, I asked her about the strange walled area — was it military? She told us about the eccentric millionaire between the wars who bought the farmhouse that stands within the peculiar 20 foot ramparts. She said he had the walls built during the depression to provide work for local people.

For his birthday I bought Bill a book — Early Birds and Boys in Blue by Phillip Jones — A century of Radnorshire aviation. On the night we returned from Cemlyn he was reading about the pioneer aviator, Vivian Vaughan Davies Hewitt, the first man to fly from Holyhead to Dublin in 1912. When Hewitt retired from flying he had moved to Cemlyn Bay, immersing himself in the bird-life and creating the walled sanctuary upon which we had just stumbled and where the wild thyme grows.

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