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.

Sabine’s Gull - Weather effects

Xema sabini

Throughout the 1980’s Sabine’s Gull occurrences were associated with south west gales, which were thought to have blown them into Cardigan Bay from the South West Approaches, which they were able to exit when the wind veered between west and north. These conditions were the result of depressions tracking along a course whereby the centres passed north eastwards over Scotland.

 Post 1992 autumn depressions began to track farther south, their centres either over Pembrokeshire or south of it. These resulted in strong south easterlies which did not have the same displacement effect on migrant seabirds. However strong northerly winds sometimes followed, blowing down the west coast of Scotland and the length of the Irish Sea, which did result in Sabine’s Gulls passing close in to the north Pembrokeshire coast.

Whichever period is examined it becomes evident that the variation in the number of Sabine’s Gulls seen depends on the frequency of “favourable” winds. Between 1980 and 1990, one to nine per annum was recorded in six years and 12 to 25 per annum in five years. Between 1991 and 2005, three to nine per annum were noted in eight years and 12 to 43 in six years. None were seen in 1993 in an autumn dominated by north east winds

Graham Rees

(Covers records up to and including 2006).

Sabine’s Gull - Ages

Xema sabini Juveniles have outnumbered adults, making up 79 % of the total recorded. Peak numbers of adults have occurred in August, whereas juveniles have peaked in September and October.

Patterns of occurrence, 1981 – 2005, adults in red, juveniles in blue, in six day periods.

Sabine's Gull - Status

Xema sabini

Scarce passage migrant.

The Sabine’s Gull is an Arctic breeding species, with an estimated total population of less than 100,000 pairs. Most breed in Canada and Eastern Russia, with about 100 – 200 pairs in Greenland and sporadic outliers in Spitzbergen.

The east Canadian and Greenland populations cross to the east Atlantic en route to winter as far south as Namibia and western South Africa. Strong winds at this time result in variable numbers passing through inshore waters.

The first to be recorded in Britain was at Milford Haven in the autumn of 1839 and another was recorded near Amroth on the 12th November 1892.The next to be recorded in the county was not until the 11th October 1968 at Skokholm.

Subsequently a total of eight birds were noted between 1970 and 1980, at Skokholm, Newgale, St David’s Head and off Fishguard. Between 1981 and 2006 they were recorded from The Smalls, the Gann, Bluck’s Pool, from the Pembroke to Rosslare ferry, Skomer, Ramsey and the Celtic Deep but principally, 95 % of the total, from Strumble Head. 

Total birds per annum.

 Records span the period from the 11th August to the 20th November, the most logged in any year being 43 in 1997, with a highest day total of 12 at Strumble Head on the 13th September 1997.

Two birds recorded do not fall within the pattern outlined above, the first being a juvenile feeding among seaweed on a Caldey Island beach on the 16th July 2005. This was remarkably early for a bird of the year to have travelled so far from where it had fledged, possibly climate change resulted in an early start to breeding.

The second was a first winter bird seen at Strumble Head on the 2nd January 1999, flying with Kittiwakes, when its smaller size and unfamiliar plumage pattern attracted observers’ attention

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.

Dusky Warbler - 2008

Phylloscopus fuscatus

Vagrant.

The Dusky Warbler breeds from Siberia to Mongolia wintering to the south but is a vagrant of annual occurrence to Britain.

The first Dusky Warbler recorded in Pembrokeshire was at Strumble Head on the 15th October 1988, being seen by Stuart Devonald, Graham Rees and John Stafford. Initially seen in the open it behaved in an agitated manner. When the observers backed off it immediately flew into deep cover in gorse. It was only subsequently viewable by using a car as a makeshift hide when it foraged on the ground.

The second to be recorded was found by Paull Grennard at Porth Clais, and was seen from the 10th to the 15th of November 2003. It was also skulking but this time in willows and with patience was seen by many observers.

Graham Rees.

(Covers records up to and including 2008).

Blue-headed Yellow Wagtail - 1894

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

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