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.