Common and Arctic Tern - 1994

Passage migrant. Not recorded from December to February

It is often difficult to separate Common from Arctic Terns, particularly at a distance, and consequently the majority of records received refer to 'Comic' Terns (Common or Arctic). The following summary is based on such records.

There is a sparse spring passage of birds passing northwards between 2 April and 30 June; Lockley (1961) also includes March but gives no specific dates. This passage is most visible from the offshore islands, when typically only small parties of up to five are seen on scattered dates, but groups of up to 14 have been noted.

They are much more frequent and numerous in the autumn, between July and late October, when they explore inshore waters to a greater extent than in spring. Some birds penetrate into the estuaries with notable gatherings at rich food sources, such as 300 off Skomer in August 1975, over 400 at Broad Haven (north) in September 1974 and 800 off St Ann's Head on 22 September 1979. This kind of incursion apart, most 'Comic' terns occurring in Pembrokeshire pass out of the Irish Sea and along the north coast, passing out to sea once clear of the Bishops and Clerks. Up to 20 pass Strumble Head daily during August and September, with occasional peaks of larger numbers, such as 277 on 3 September 1983 (926 birds were logged in the autumn of 1983, between 12 August and 23 October), and 458 on 27 August 1990 (848 birds were seen passing on the three days from 26 to 28 August).

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