Manx Shearwater – 1994

Puffinus puffinus – ADERYN-DRYCIN MANAW – Numerous breeding summer visitor. Recorded in all months

Breeding confirmed3
Breeding probable
Breeding possible
No of tetrads occupied3 (of 478)
Percentage of tetrads0.6%

The Manx Shearwater figures as the emblem of the Dyfed Wildlife Trust, an appropriate choice since internationally important numbers of the bird breed on its island reserves of Skomer (estimated 95,000 pairs in 1971 and 165,000 pairs in 1989) and Skokholm (35,000 pairs estimated in 1973). Small colonies also occupy Middleholm and North Bishop. Large numbers probably bred on Ramsey prior to the invasion of the island by brown rats, which is estimated to have taken place in around 1800 (Saunders, 1986). However, by the end of the nineteenth century numbers had greatly reduced, and Mathew (1894) could only suggest that “a few may breed”. No definite breeding records on Ramsey have been traced for subsequent years until R. Pratt’s record of 200 pairs in 1975 and the RSPB estimate of 300-400 pairs in 1992. In the past, Manx Shearwaters also bred on Caldey and perhaps St Margaret’s Island (Mathew 1894).

Manx Shearwaters return to the breeding colonies in late February and depart from late August, some young not leaving until well into October. They visit the nesting burrows only at night, a stratagem which limits the effects of predation by gulls.

They use all the sea areas around the county for feeding, particularly the southern Celtic Deep, increasing numbers penetrating further northwards as the season progresses. Varying numbers also use the Bristol Channel, sometimes following fish shoals as far upstream as the Severn Bridge. Large processions can be seen passing our headlands each evening as they head for the island colonies, assembling in rafts on the water to the seaward side to await nightfall before moving ashore.

A few remain in local waters throughout the winter but the majority cross the Atlantic to winter off the coast of South America, where they are found mainly between latitiudes 20°S and 30°S until December. Return passage may be by way of the west African coast and certainly through the Bay of Biscay. Some first and second year birds summer off Newfoundland and Nova Scotia while others return to their natal colonies, and also visit colonies elsewhere in the Irish Sea and possibly Scotland. Extreme ringing recoveries include a Skokholm­bred bird that wandered as far as South Australia by the beginning of its second year, and an eight- year old in Norwegian waters during May.

Some fledglings wander inland when they leave the colonies, with onshore gales blowing many into the Cleddau Estuary and beyond, sometimes as far as eastern England. The gales also result in passages of thousands off Strumble Head. Many of these could have drifted downwind into the Irish Sea to beat back out to regain their ‘ground’ but it is highly likely that some could be Scottish birds passing southwards through the Irish Sea.

Donovan J.W. & Rees G.H, 1994, Birds of Pembrokeshire

SAUNDERS, DR 1986. The Nature of West Wales. Barracuda Books

More about the Manx Shearwater in Pembrokeshire