Sooty Shearwater - analysis
Friday, December 24, 2010 at 1:01PM Puffinus griseus
The number of Sooty Shearwaters seen has been dependent on the nature of the weather systems occurring during the peak passage time, August to September. A trickle of small numbers were recorded during light to moderate winds, larger numbers in more turbulent weather.
During the 1980’s Atlantic depressions moving south-west to north-east with their centres passing over Northern Ireland and Scotland were prevalent. Locally these produced south-west gales which veered north-west before moderating when the system progressed further to the north-east.
The south-west component is thought to have displaced shearwaters from the Western Approaches into the Irish Sea. They were able to make their way back southwards when the wind wore around to the north-west, many of them passing close in to the north Pembrokeshire shore in the process. The largest counts of Sooty Shearwaters at Strumble Head were made during these conditions, i.e. 237 on the 1st September 1985 and 397 on the 3rd September 1983.
The depressions that occurred in August and September between 1990 and 2006 tracked further south with their centres over Pembrokeshire or further to the south. These systems did not produce the south-west going north-west winds locally, indeed they often produced easterly winds which did not prove favourable for placing Sooty Shearwaters in Pembrokeshire waters.
They did occasionally produce strong north winds blowing through the North Channel and down the Irish Sea, which pushed some Sooty Shearwaters close to the north Pembrokeshire shores but in lesser numbers than during the 1980’s. Counts between 11 and 35 were made on peak days, the maximum being 42 on the 14th September 2004.
Breakdown of Strumble Head totals
1980 - 89 1736
1990 - 99 645
2000 - 06 474
Graham Rees
(Covers records up to and including 2006)
