Common Scoter - 2010 ringing recoveries

"Sea Empress" scoter ringing recoveries - what have we learned so far?

Back in those dark days of Feb 1996, some 4,571 common scoters were found dead/dying in and around Carmarthen Bay as a direct result of the "Sea Empress" oil spill. However many oiled scoter were rescued, cleaned and released, even though the sceptics said it was a waste of time - they were unlikely to survive long.

Back in 1996, next to nothing was known of the origins of scoter wintering in the Bay. By ringing the cleaned birds (later released from rehab centres in cleaner waters off the Welsh coast and in southern England) it was hoped that at least something positive would come out of this disaster. So what have we learned so far?

About 70 scoters were recovered shortly after being released around the coast of south-west Wales and southern England. But one unlucky victim was oiled again by the "Tricolor" spill off the Dutch coast in late January 2003 having survived seven years after release (this one was among 60 scoters found oiled).

Now, almost 14 years on, it is interesting to note that there have been three "Sea Empress"-ringed scoter recoveries in Russia (one west of the Urals and two further east in the province of Yamalo-nenets) the most recent of these being found (shot) in June 2009 - thirteen years after being cleaned and then released.

So all the effort put in by volunteers in Milford Haven and around West Wales and elsewhere, to try and help these birds recover from their ordeal, was certainly worth it. More information on the BTO ringing blog from where the following map was borrowed.

Bob Haycock, Pembrokeshire Bird Blog

Common Scoter - 1994

Winter visitor and passage migrant

Mathew (1894) stated that the Common Scoter was a "not rare" winter visitor, while Lloyd was the first to notice large numbers in Carmarthen and St Bride's bays during the 1920s and 1930s, including flocks during the summer months. Lockley et al. (1949) referred to summer flocks of up to 400 in both bays. Thereafter, many observers contributed observations which established that the Common Scoter is present in our waters throughout the year. Seawatching at Strumble Head from 1980 onwards has permitted seasonal movements to be used to interpret the overall pattern of occurrence.

Male Common Scoters generally winter further south than females (Cramp 1977). Large numbers winter in Carmarthen Bay (West Glamorgan— Carmarthenshire—Pembrokeshire), males conspicuously outnumbering females here. It is difficult to estimate how many birds are present in this huge area, but a series of aerial counts conducted by the RSPB in the 1970s indicated that over 5,000 Common Scoters were present each winter. A further 1,000-2,500 winter in St Bride's Bay where, surprisingly, males are outnumbered by females in the approximate proportion of 4:1.

The aerial surveys of Carmarthen Bay, and other counts made from boats, indicate that much larger numbers are present in March than in mid-winter, for example 25,000 between Saundersfoot and Worm's Head on 13 March 1974. This may mean that the Bay is used as a migration staging area, perhaps involving Common Scoters moving up from further south. However, apart from "over 100 passing northwards" off the South Bishop on 18 April 1976 (McCanch 1985) no visible spring movement has been detected in Pembrokeshire. It seems likely, therefore, that the main departure takes place at night. Kumari (1979) has established that Common Scoters do migrate at night, from his radar studies in the White Sea and the Baltic.

Not all leave Carmarthen Bay in the spring, presumably those remaining being non-breeders which complete their moult there. The situation in St Bride's Bay at this season is not clear. A southward passage past Strumble Head, through St Bride's Bay and then eastwards past St Govan's Head, during June and July, is thought to include males returning from their breeding grounds and making their way to Carmarthen Bay to moult. Later movements, peaking in October and November, include a larger proportion of females and these would be post-moult birds heading for their winter quarters. Fewer Common Scoters have been recorded passing St Ives in Cornwall than pass Strumble during these movements, which may indicate that our passages include birds that winter further south. The timing of the movements, coupled with a synchronous passage across the middle of England, suggests that the majority of the Common Scoters seen in Pembrokeshire are from the Fenno—Russian breeding population. A recovery of one bird in Lancashire in December that had been ringed in Finland in October supports this hypothesis, but the recovery of another that had been ringed in Iceland means that the situation may be more complex.

Common Scoters are vulnerable to oil spills and casualties were noted in 1950 and again in 1973-1974, on each occasion about 300 being found contaminated and stranded on the Pembrokeshire shoreline of Carmarthen Bay.

A male Black Scoter, subspecies americana, was at Newgale from November 1991 to March 1992 (D. Astins et al.).

Donovan J.W. & Rees G.H (1994), Birds of Pembrokeshire

Update on Monday, January 30, 2017 at 10:33AM by Pembrokeshire Avifauna committee

Black Scoter Melanitta americana is now recognised as a separate species

see article by Martin Garner

Common Scoter - 1980s winter atlas

The BTO winter atlas showed that Common Scoters were present in a few coastal and estuarine 10km squares during the winters of 1981-82, 1982-82 and 1983-84.

The darker the colour, the higher the relative total count for each 10km square.  The darkest blue represents more than 96 birds. Up to 420 were recorded in St Bride’s Bay (SM 81 & 82) and 650 off Amroth (SN 10) during this period.

Graham Rees