Arctic Tern

Sterna paradisaea

Passage migrant.

The Arctic Tern has a continuous circumpolar Arctic and sub Arctic breeding range, the nearest nesting in Wales being at Anglesey and in Ireland in county Wexford. The species winters as far south as the edge of the Antarctic ice and there are ring recoveries of Anglesey birds off South Africa and Australia.

Mathew (1894) stated that the Arctic Tern was “seen commonly on passage in spring and autumn”, but Lockley et al (1949) later noted that they were “no longer seen commonly on passage” and noted just three occurrences, singles at Goodwick on the 13th August 1935 and at Skokholm on the 8th June 1938, with 20 at Dale at the end of April 1947. Donovan and Rees (1994) considered the Arctic Tern to be sparsely recorded in spring when up to eight at a time were seen passing, mainly off the west coast and offshore islands, between the 13th April and the 23rd June, but more numerous in autumn, when up to 30 in a day passed between the 21st July and the 22nd November, principally seen off the north coast.

Any detailed assessment of the Arctic Tern’s status is limited by the fact that only a proportion of Common or Arctic Terns are identified to species, most being logged as “Common or Arctic” , usually expressed as “Commic Tern” . What can be gleaned is that 130 were recorded at Skokholm on the 1st September 1997 and that single birds were recorded away from the coast at Heathfield Gravel Pit on the 23rd September 1999, at Bosherston on the 8-9th May 2000 and at Llawhaden on the 11th May 2000. 

See also the account for Common or Arctic Tern.

Graham Rees.

(Covers records up to and including 2009).

Common or Arctic Tern - Autumn

Sterna hirundo/ paradisaea  

Many more pass through on autumn passage, July to October, than in spring, with occasional accumulations of 100 to 800 birds having been noted off St Ann’s Head, Skokholm, Broad Haven (north) and sea area between Point St John, St David’s Head and the Bishops and Clerks as far out as Bais Bank. However, the majority have been recorded passing along the north coast at Strumble Head. Normally up to 30 per day were seen but periodically larger passages occurred, the largest on record being 190 on the 11th September 1984, 458 on 2nd September 1988, 459 on 27th August 1990, 256 on 11th September 1992, 363 on 4th September 1997, 375 on 1st September 1998, 199 on 17th August 2002, 726 on 31st August 2005 (an additional 151 Common Terns identified as well) and 501 on 8th September 2009.

These large movements have occurred with moderate to strong south or south-east winds, usually accompanied by poor visibility due to rain or drizzle. The terns have arrived on a north-west to south-east track, suggesting they had come from the Wicklow coastal area. The exception was on the 27/8/90 when they arrived from a north-easterly direction, presumably caused by a previous accumulation in Cardigan Bay moving on en masse, there being a moderate south-west wind and good visibility at the time.

Many more Common than Arctic Terns are identified in the county, so probably make up the majority of reported “Commics”.

Graham Rees.

(Covers records up to and including 2009).

Common or Arctic Tern - Spring

terna hirundo/ paradisaea

Spring passage has been recorded from the 29th March to mid June, with stragglers to the end of June, the majority of birds being seen in late April and the first three weeks of May. Most were seen to the west of Skokholm, Skomer and Ramsey, with very few along the north coast but small numbers off the south coast. Most sightings were of one to five birds but up to 18 together have been seen. Those seen moving along the south coast could conceivably have continued their migration up the Bristol Channel and through the Severn valley.

Common or Arctic Tern - status

Sterna hirundo/ paradisaea

Passage migrant.

It is not always possible to separate Common from Arctic Terns in the field unless they are close and seen well. However, most observers still wish to record what they see and log these birds as either “Common or Arctic”, usually expressed as “Commic Terns”. The following is a review of such records.

 There has been a marked difference in the nature of spring and autumn passages. There are many breeding colonies of both species to the north and west of Pembrokeshire along the coastlines of both western Britain and eastern Ireland, which are probably the origin of most passing the county. Whereas there has usually been a strong passage of birds migrating southwards from these colonies in the post breeding season, comparatively few have been seen passing northwards on their way to the breeding grounds. Although there are juveniles as well as adults swelling the population in the autumn, this alone does not fully explain the discrepancy in the volume seen. It seems more likely that having spent a pelagic winter season most spring birds pass Pembrokeshire out of sight of land, which would explain why the majority that are detected are to seaward of the islands beyond the west coast and increasing numbers are seen from land further up the narrowing Irish Sea. It is interesting to note in this context that in the spring of 1984, when direct comparison was possible, twice as many were seen passing The Smalls compared to Skokholm. As with other species of migrant birds, spring passage is performed with a sense of urgency to reach the breeding grounds at an optimal time, so is a rapid event. By comparison autumn migrants do not need to travel to their wintering areas according to such a strict schedule, being able to pause and accumulate at rich feeding sources en route.