Black-throated Diver - 1949

Colymbus stellatus

Almost as frequent as great northern diver in winter, and in the same situations

R.M.Lockley, G.C.S.Ingram, H.M.Salmon, 1949, The Birds of Pembrokeshire, The West Wales Field Society

Black-throated Diver -1994

Scarce winter visitor and passage migrant. Recorded in all months except June, July and August.

Mathew (1894) classified the Black-throated Diver as a winter visitor on the strength of it being included in one of his correspondent's lists, whereas Lockley et al. (1949) considered it "almost as frequent as the Great Northern Diver in winter". Dickenson and Howells (1962) stated it "has always been, and still is, an uncommon bird" in Pembrokeshire, and Saunders (1976) classified it as "scarce" and the rarest of the divers. There has been an increase in the number of active observers in Pembrokeshire in recent decades with superior optical aids to those available in the past, revealing the Black-throated Diver to be a regular winter visitor and passage migrant in small numbers. It is probably still slightly under recorded, divers often being tantalisingly just too far away for certain identification. Nonetheless it has been recorded from all around the outer coast at one time or another, Fishguard Harbour, Strumble Head, St Bride's Bay and the Amroth—Saundersfoot area being the localities from which it is most often reported. Usually one or two birds are seen, occasionally three or four and perhaps a dozen are spread around the county coastline each winter. Has only been recorded inland at Llysyfran reservoir and is the only diver to have been recorded as far out to sea as the Smalls.

A few birds have been noted in full summer plumage, in the months of May, September and October.

Black-throated Diver - 1980s winter

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.

Black-throated Diver - 1894

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

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