Puffinus gravis – ADERYN-DRYCIN MAWR – Near annual passage migrant
The Great Shearwater breeds on islands in the Tristan da Cunha group, Gough Island and Kidney Island in the Falklands. Outside the breeding season they migrate up the western Atlantic to Newfoundland, spreading to Greenland and the Denmark Strait. They return southwards on the eastern side of the Atlantic, passing between July and November. They normally travel well offshore but onshore winds push a proportion close to the coast of Western Europe.
The first one recorded in Pembrokeshire was on the 15th August 1957, when C. M. Swaine watched it passing through Jack Sound, the channel between Middleholm and the mainland. Between 1973, when it was next recorded, and 2007 a total of 228 birds were logged. All were between July and October, the earliest one off South Bishop on 14th July 1975, the latest off Skomer on 29th October 1994.
The majority, 128 birds, were seen from Strumble Head, a further 8 from the islands of Skokholm, Skomer, Ramsey and South Bishop combined.
For a species known to mainly travel well offshore it might be expected that the majority passing through the Irish Sea would be out of sight from land. Opportunities to detect these have been limited by the cost and availability of suitable boats and rough weather sometimes limiting their use. Despite these restrictions a total of 93 birds have been logged in the offshore waters of Pembrokeshire.
A group of 23 were flushed by the passing Fishguard to Rosslare ferry on the 15th September 1981. Five sightings of single birds were made from the Smalls during the autumn of 1982 – 84 when there were daily observations from the lighthouse. One was seen south of Caldey on the 4th August 1991 from the Cork to Swansea ferry. Three were seen from the Fishguard to Rosslare ferry on the 10th September 1999. Two were logged about 10 miles north of the Smalls on the 8th September 2006 from a ship on passage from the USA to Liverpool.
A total of 59 were encountered between 1998 and 2002 from shark–fishing vessels hired to visit the Celtic Deep area.
The largest incursions into our waters were in 1999 when a total of 41 was logged in the Celtic Deep compared to 11 inshore off Strumble Head and in 2002 when 17 were seen in the Celtic Deep and 29 recorded at Strumble Head.
Further offshore observations from boats could throw further light on the pattern of occurrence of this species, as in some years few, or none, might pass through the Irish Sea. Using the data so far available, 85 % more birds were seen offshore than from the land on dates when weather permitted hire vessels to go to sea and simultaneous observations could be made from land.
The largest numbers seen from land have mostly been when strong onshore winds have prevented offshore observations. The county day maximum of 25 was recorded passing Strumble Head on the 31st August 2002 when the sea was too rough for small craft to put out to sea. It is possible that observation from a large vessel offshore that day might have revealed a greater presence than has so far been indicated. Resolving such observational incompatibilities presents a challenge.