Cory’s Shearwater

Calonectris diomedea

Erratic visitor.

The Cory’s Shearwater breeds in several places around the Mediterranean, in Portugal and on the sub tropical islands of the east Atlantic. It is migratory outside the breeding season, many then occurring in the Bay of Biscay, regularly penetrating as far as Cornwall and occasionally appearing in large numbers off the south west of Ireland.

It is an erratic visitor to Pembrokeshire waters, being first recorded from the Fishguard to Rosslare ferry on the 25th September 1965 by Jack Donovan. From then until 2007 a total of 86 birds have been logged. They were not recorded annually, being seen in 66 % of those years. The earliest was off the South Bishop on the 22nd February 1976, the latest off Strumble Head on the 29th November 1999. Otherwise the cumulative monthly totals were:

Most sightings involved single birds, with two in a day on five occasions, three once, five twice and the maxima of six in the Celtic Deep on the 26th September 1999 and seven off Strumble Head on the 15th August 1999. The largest incursion was in 1999 with a total of 26 bird days logged.

Considered by BWP as “equally satisfied with pelagic, offshore and inshore waters”, the fact that 78 % of Pembrokeshire sightings were made from the land, probably reflects the distribution of observer effort. A total of 14 of these were seen from Skokholm, Skomer, St Ann’s Head, South Bishop, Ramsey and St Govan’s Head, and 53 from Strumble Head. The hours of observation expended from the land greatly exceeded the time spent looking in offshore waters.

Offshore sightings were of singles from the Fishguard to Rosslare ferry, from a small craft west of Grassholm and from another boat north of Porth Gain, five from the Pembroke to Rosslare ferry and 11 from shark-fishing vessels in the Celtic Deep.

Cory’s Shearwaters have been seen in Pembrokeshire waters in a variety of weather conditions, with winds from all directions and ranging from calm through moderate winds to full gale force, making their appearance unpredictable.

It is not known to what degree the races Calonectris diomedia deomedia and C.d. borealis are involved in the Pembrokeshire record.

Graham Rees

(Covers records up to and including 2007)

References

CRAMP. S. (Editor), 1977 – 1994. Handbook of the Birds of Europe, the Middle East and North Africa : the birds of the Western Palearctic, Oxford University Press, 9 Vols.

Great Shearwater - discussion

Puffinus gravis

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.

Graham Rees

(Covers records up to and including 2007)

Great Shearwater - Where seen

Puffinus gravis

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.

Great Shearwater - Status

Puffinus gravis

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.

Balearic Shearwater - Analysis of Strumble Head records

Puffinus mauretanicus

From one to five birds per occasion were recorded from Skokholm, Skomer, Grassholm, Ramsey,

Whitesands Bay, St David’s Head, Fishguard Bay, St Govan’s Head, from the Rosslare to Fishguard ferry and in the Celtic Deep area. However intensive watching at Strumble Head revealed a greater presence in local waters than observations elsewhere hitherto suggested.  

The annual totals are probably over-estimates as they would include individuals remaining in the observation area for more than one date. Unlike most other seabirds which are generally seen passing north to south through local waters in the autumn, Balearic Shearwaters arrive from the south in search of food and are often seen feeding offshore.

Hours of observation

 

The number seen has varied from year to year.  The hours of observation compared with birds seen indicates that this was not just a consequence of observer effort. The trend over the 23 year period was of increase.

This was part of an increase noted throughout south west Britain at this time, demonstrated by Wynn and Yesou (2007), which was probably due to a warming of the sea surface causing small fish shoals, the prey of this species, to move  further north than in the past.

Most were recorded between July and November, the largest numbers between August and October. Counts at Strumble Head have usually consisted of one to six birds per day but rising to about 20 when strong northerly winds blew. Higher counts of 33 on the 4th October 1996, 36 on the 2nd October 1999, 37 on the 22nd September 2003 and the maximum recorded of 93 on the 7th October 2006, occurred when there were strong northerly winds, which pushed birds closer inshore than they might otherwise have approached. Exceptional numbers of Balearic Shearwaters were seen in the waters of south west Britain including Wales, in the autumn of 2006.

Patterns of occurrence at Strumble Head: total numbers.

 There have been a few sightings outside the July to November period: once at the Smalls in December 1984 and January 1983, 10 times in eight different years at Strumble Head in December and 10 times in four years in January. None have been recorded in March but singles have been noted at Skomer on the 25th April 1991, at Skokholm on the 15th May 1997, from the Fishguard to Rosslare ferry on the 25th May 1997, near Grassholm on the 2nd June 1993, off Strumble Head on the 2nd February 2002, 16th April 1990, 2nd June 1993, 2nd June 1996 and 8th June 1987. 

From time to time observers have pointed out that some shearwaters seen in Pembrokeshire waters resemble Yelkouan Shearwater. Other observers considered these birds could be particularly pale Balearic Shearwaters. Those breeding on Manorca would appear to exhibit mixed characteristics of both Balearic and Yelkouan Shearwaters, further clouding the issue.

Graham Rees

(Covers records up to and including 2006)

References

WYNN. R. And YESOU. P. 2007. The changing status of Balearic Shearwater in northwest European waters, British Birds, Vol. 100, 392 – 406.

Balearic Shearwater - Status

Puffinus mauretanicus

Status: annual visitor.

Balearic Shearwaters are only known to breed on the Balearic Islands in the western Mediterranean. There is a known breeding population of only 2,000 – 2,500 pairs, which makes it one of the most vulnerable seabirds in the world. Post breeding dispersal has regularly resulted in a proportion visiting the Bay of Biscay and south-west Britain and Ireland.

A specimen housed in the Museum of Comparative Zoology, Harvard, USA, collected in Pembrokeshire waters in September 1900, was the first to be recorded in the county.

 It was next recorded when one was seen from a boat near The Smalls on the 7th July 1955. Balearic Shearwaters were then noted in 11 years between 1960 and 1975 and annually from 1980.

Manx Shearwater - 1894

Species account from M Mathew, 1894, "The Birds of Pembrokeshire and its islands"

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