Xema sabini – Gwylan Sabine – 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
Age of birds
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.
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. Pembrokeshire County Bird Recorder 1981-2007