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.

Arctic Skua - Age and morph

Stercorarius parasiticus

Age and or morph was recorded for the bulk of the Arctic Skuas seen at Strumble Head between 1980 and 2006. Adults made up 67 % of the total, of which 31 % were light–phase, 33 % dark–phase and 3 % classified as intermediates, the remaining 33 % of the total were predominantly juveniles, though some first and second year birds were identified.

Graham Rees.

(Covers records up to and including 2007).

Arctic Skua - Spring

Stercorarius parasiticus

The Arctic Skua has been sparse in Pembrokeshire waters during spring, with one to three per annum being the norm during the period 1958 to 2003, passing between the 4th April and the 30th June. Four in 1998, six in 1996, eight in 2002 and 10 in 1993 exceeded the norm. Records came from Tenby, Broad Haven (S), St Govan’s Head, West Blockhouse, St Ann’s Head, Skokholm, Skomer, The Smalls, St Bride’s Bay and Strumble Head.

Graham Rees.

(Covers records up to and including 2007).

Arctic Skua - Autumn

Stercorarius parasiticus

The number of birds involved each autumn varied, extremes being 67 in 1993 and 355 in 1985. Differing breeding success no doubt played a part in this variability but changing weather systems seem to have been the main factor.

Autumn totals at Strumble Head, 1980 – 2007.

 Passage has been recorded from July to December, at Strumble Head between 1980 and 2006, a total of 24 being seen in July, 32 in November and 5 in December. Totals for the months August to October, expressed in six day periods were:

Light to moderate winds with a westerly component prevailed in most autumns. It was thought that some of the Arctic Skuas travelling southwards through the Irish Sea were drifted eastwards into Cardigan Bay by these westerly winds. When the skuas encountered the north Pembrokeshire coast they followed it in a westerly direction, so as to gain sea room for their continued southward migration. When south–westerly gales occurred larger numbers appeared in Cardigan Bay, presumed to have been blown there from the sea area south of the Irish Sea. When the wind veered to between west and north before moderating, these birds were able to make their way back out to sea, many of them passing close in to Strumble Head. It was such a weather system that resulted in the largest day total recorded when 103 passed on the 3rd September 1983.

Light to moderate north–east winds predominated in the autumn of 1993 and few Arctic Skuas were seen, most of those that did pass were during short interludes of westerly winds. Strong winds from due east dominated the autumn of 2003 when a total of 203 Arctic Skuas was logged passing. Such winds could be expected to drift southward travelling birds away from Cardigan Bay, so it seems likely that those seen at Strumble Head had arrived by flying overland from the North Sea assisted by the following wind.

Observational evidence indicates that Arctic Skuas are diffusely spread once they have cleared the north coast of the county. Daily observations from The Smalls throughout the autumns of 1983 and 1984 recorded far fewer birds than passed Strumble Head on the same dates. Offshore watchers using boats going as far out as the Celtic Deep only occasionally encountered one or two Arctic Skuas, as was the case with shore based watchers on the west and south coasts of the county and on the offshore islands. At Skokholm the mean autumn total from 1953 to 2003 was seven birds.

 Graham Rees.

(Covers records up to and including 2007).

Arctic Skua - Status

 Stercorarius parasiticus

Passage migrant.

The Arctic Skua has a circumpolar Arctic breeding distribution extending southwards to northern Scotland. Migrants seen passing through British waters are en route to and from Atlantic wintering areas, principally south of the equator.

Mathew (1894) noted just one record of an Arctic Skua, shot at Goodwick, but gave no date. Lockley et al (1949) considered it to be occasional off Skokholm and Grassholm, mainly in August and September but sometimes in May or June.

A mean of 10 per annum was recorded in the county between 1953 and 1975, during a period when little seawatching was conducted. The low detection rate being linked to a paucity of watching was emphasised when Saunders (1976) noted 45 passing Strumble Head on the 8th September 1974. Watching at this headland became more frequent from 1978, with regular autumn observations from 1980 onwards. The annual average total of Arctic Skuas recorded in Pembrokeshire between 1980 and 2003 rose to 235, 90 % of them being seen at Strumble Head, passage taking place between July and November, the majority between August and October.

Graham Rees.

(Covers records up to and including 2007).

Great Northern Diver - ages

Gavia immer

Observers have seldom included an age assessment in their reports unless noting adults in summer plumage.  

Great Northern Divers have a prolonged post breeding moult period stretching from September to January, consequently birds in summer plumage have been recorded throughout autumn passage, occasionally as late as the end of December. Of a total of 646 birds closely scrutinised passing Strumble Head in autumn, between 1981 and 2008, 48% were in full or showed variable vestiges of summer plumage.

A few birds have been recorded in full summer plumage in the spring, from late April.

Graham Rees

(Covers records up to and including 2008)

Great Northern Diver - spring passage

Gavia immer

Spring passage has been relatively small, mostly recorded as departure dates from wintering areas, normally completed by late March to early April. Occasionally presumed migrants have briefly appeared at some of these same places in late April up to 22nd May and others have been noted at or passing headlands and the offshore islands from late March to 26th May. Later occurrences were: one in the Gann – Lindsway Bay region throughout May until at least the 21st June 1991 and two at Ceibwr on 22nd June 1997. 

Great Northern Diver - autumn passage

Gavia immer

The variation in county annual totals seems to have had more to do with variation in the number of passage migrants recorded than with the number of wintering birds. Autumn passage has been noted along the coast and at the offshore islands, being most consistently documented at Strumble Head annually between 1983 and 2006.

The earliest recorded there was on 28th July 1991. August records were all of single birds, on the 31st in 1985, 24th in 1986, 28th in 1989, 23rd in 1994, 28th in 1994 and 27th in 1995. Numbers built up in September, the main passage taking place from October to December:

Totals have been grouped into six day periods, except that the last readings for October and December have been adjusted from seven day totals. This has been done by dividing the seven day totals by seven, then multiplying by six.

Great Northern Diver - winter

Gavia immer

In winter they have been found in the offshore waters all around the coast from Cemaes Head to Amroth, including Fishguard harbour.

Most sightings have been of single birds or sometimes two together, with occasionally up to seven in areas such as St Bride’s bay, Fishguard Harbour and the Strumble Head tide races. The unusual gathering of 43 at Strumble Head on 6th January 1991 was probably due to birds seeking a lee shore during a period of prolonged SW gales.

Great Northern Divers have regularly been seen within the Milford Haven / Cleddau Estuary waterway during the winter months, January to April and October to December. The average number recorded between the years 1983 and 2003 was five, the maxima in a year being 10 in 2002 and 12 in 1999, which probably included some migrants in transit.

Most records were from the area between Dale and Hakin, including the Gann, Angle Bay and the Pembroke River. Singles have been seen further upstream at Castle Pill, Llanstadwell, Neyland, Lawrenny, Cresswell and Carew Rivers, including the tidal Carew Mill Pond, Garron Pill, Beggars’s Reach,  Llangwm and Landshipping to Hook Reach area.

The only fresh water occurrences on record are of one at Bosherston 9th – 13th November 1986, two at Llys y fran Reservoir 16th January 1986, with singles there in 1983, 1984, 1985, 1999, 2001, 2002 and 2006.

Great Northern Diver - status

 Gavia immer

Winter visitor and passage migrant.

The Great Northern Diver breeds across the sub Arctic region of the Americas, Greenland and Iceland and on rare occasions has bred in Scotland and as far east as Svalbard.  Those that winter in the east Atlantic do so as far south as the Bay of Biscay and Iberia.

As with many other species, it is difficult to assess the Great Northern’s status in Pembrokeshire in the past. The accounts of previous authorities have been largely anecdotal and prone to expressions like “sometimes numerous” and “frequently seen”.

Dickenson and Howells (1962) must have felt sufficiently able to interpret the past to state “From the numbers recorded in the last decade it is possible that a decrease has taken place since the 1930’s.” The decade they referred to was 1952 to 1961, when an average of three per annum was recorded, the maximum in any year being nine in 1959.

The average recorded per annum remained at three until 1982, the maximum in a year being six in 1972. By 1983 an increasing number of observers were putting the results of their observations into the communal record and from then until 2006 the average number recorded reached 61 per annum, with the most in a year being 119 in 1999:

There was a marked increase in the number of active observers during the 1980’s and 1990’s, they possessed ever improving optical aids and most had the discipline to contribute their observations to the communal record. These are likely to be the factors that explain the upsurge in records, rather than there being an increase in the number of Great Northern Divers visiting Pembrokeshire.

References

DICKENSON. H and HOWELLS. R. J. 1962. Divers in Wales, Nature in Wales 8.

DONOVAN. J and REES. G. 1994. Birds of Pembrokeshire, Dyfed Wildlife Trust.

LLOYD. B. 1929-1939 Diaries, National Museum of Wales.

LOCKLEY. R. M, INGRAM. C. S. and SALMON. H. M.1949. The birds of Pembrokeshire, West Wales Field Society.

MATHEW. M. 1894. The birds of Pembrokeshire and its islands, R. H. Porter.

Black-throated Diver - passage

Gavia arctica

Donovan and Rees (1994) pointed out that the Black-throated Diver was a passage migrant as well as a winter visitor to Pembrokeshire. Passage has involved occasional birds flying southwards along the coastline and passing the offshore islands, mostly between September and December, although singles were recorded passing Strumble Head on 20th August 1997 and 21st August 1999 and one was at Lydstep Haven on 30th August 1988.

The number of migrants recorded has been small, with an average of nine per annum between 1983 and 2003, the most in any year being 29 in 1999. Passage has been well documented at Strumble Head, where the total between the years 1983 and 2006 is tabulated by month :

Sep - 8

Oct - 45

Nov - 85

Dec - 31

Most Black–throated Divers have departed the county by the end of March but there are 11 April records and four for May, the latest being one at Broad Haven (North) on the 25th in 1961, perhaps indicating birds passing through.

The Black–throated Diver has not been recorded in Pembrokeshire in June and July.

Graham Rees

(Covers records up to and including those for 2006)

Black-throated Diver - Winter

Gavia arctica

Winter visitor and passage migrant

The Black –throated Diver has an Arctic breeding distribution, stretching from Siberia to Iceland extending as far south as Scotland. Those occurring on the eastern side of the Atlantic migrate to winter as far south as the Bay of Biscay and north-west Spain. Gavia arctica pacifica from North America and N E Siberia is currently considered as a separate species.

Previous commentators have assessed the Black – throated Diver in Pembrokeshire as a scarce winter visitor. 

In winter they have been recorded in offshore waters all around the outer coast, once as far out as The Smalls, on 22nd January 1982. Because they can be difficult to detect and identify in the often choppy sea, they may be under recorded. Donovan and Rees (1994) suggested that perhaps a dozen were spread around the coastline each winter. The records for 1983 – 2003 show an average of six to seven detected each year, however nine were noted in four different years and 10 in 1997.

They have been noted within the Milford Haven / Cleddau Estuary waterway 14 times in eight different years, all single birds apart from two at Neyland on 28th December 1963.

Most were noted around Dale and the Gann but also once each at Angle Bay and Pembroke Dock, as far up the estuary as Landshipping on 31st December 1963 and at Lawrenny on 1st January 1997 which had reached Landshipping by February.

One which collided with the Cleddau Bridge during a storm in the late winter of 1996, was rescued by the Texaco Bird Hospital, rehabilitated and released at Lawrenny just before the end of the year. This bird probably accounts for the records at Lawrenny and Landshipping in January and February 1997 noted above.

The only record away from salt water was of two at Llys y fran Reservoir on 22nd February 1986.

An oiled bird was on the Teifi at Cilgerran on 19th & 20th March 1995 and two oiled birds were recovered during the Sea Empress oil spill of 1996.

Total birds on record : 1982 – 2006

References

DICKENSON. H and HOWELLS. R. J. 1962. Divers in Wales, Nature in Wales 8.

DONOVAN. J and REES. G. 1994. Birds of Pembrokeshire, Dyfed Wildlife Trust.

LLOYD. B. 1929-1939 Diaries, National Museum of Wales.

LOCKLEY. R. M, INGRAM. C. S. and SALMON. H. M.1949. The birds of Pembrokeshire, West Wales Field Society.

MATHEW. M. 1894. The birds of Pembrokeshire and its islands, R. H. Porter.