Celtic Deep Pelagic

The West Coast Birdwatching Celtic Deep Pelagic is Pembrokeshire's dedicated offshore seabird expedition, led by local expert birding guide Dave Astins since 2021. Departing from Neyland on the Milford Haven waterway in southwest Wales, the trip heads offshore aboard Dale Sailing's Helen Claire — a twin-hulled speedster that makes rapid passage to the Celtic Deep, the deep-water zone of the eastern Celtic Sea where depths reach 100 metres and cold, nutrient-rich Atlantic water creates highly productive seabird feeding conditions. The twin-hull design provides exceptional stability while the boat drifts and chumming is deployed to attract passing pelagic birds to inspect the vessel. The Celtic Deep lies approximately 40–50 nautical miles southwest of Pembrokeshire, placing it well beyond the continental shelf break where truly oceanic tubenoses and skuas concentrate in late summer and autumn.

Since 2021, Wilson's Storm-Petrel has been recorded on every single Celtic Deep pelagic, placing Pembrokeshire firmly within the northeast Atlantic's peak encounter zone for this remarkable species. This tiny, swallow-sized storm-petrel — barely larger than a House Martin — breeds in enormous numbers on sub-Antarctic islands and undertakes an extraordinary transoceanic migration north into the Atlantic each boreal summer. The 2024 season produced a new Welsh record of four Wilson's Storm-Petrels on a single trip, a remarkable concentration for Welsh waters and a testament to the productivity of the Celtic Deep during the late summer passage peak. European Storm-Petrel (Hydrobates pelagicus) — the smallest European seabird, breeding in globally significant numbers on nearby Skokholm and Skomer Islands — is described by Dave Astins as "almost guaranteed" on the Celtic Deep pelagics, fluttering low over the waves in the boat's wake with the characteristic moth-like flight that makes this species so distinctive and endearing.

Great Shearwater (Ardenna gravis) has been recorded on every Celtic Deep pelagic since 2021. This large, strikingly patterned shearwater breeds almost exclusively on remote South Atlantic islands — primarily Tristan da Cunha and Nightingale Island — and migrates north through the Atlantic each summer in extraordinary numbers, with the Celtic Sea lying directly on its peak dispersal pathway through European waters. Great Shearwaters in the Celtic Deep are regularly seen in multi-species flocks alongside Manx Shearwater (Puffinus puffinus), which breeds in globally significant numbers on Skomer (the world's largest single colony) and Skokholm. The surrounding Celtic Sea is their primary feeding ground during the breeding season, and flocks of Manx Shearwaters numbering in the hundreds are commonly witnessed from the Celtic Deep pelagic between July and September. Cory's/Scopoli's Shearwater (Calonectris borealis/diomedea) — breeding on Mediterranean and Macaronesian islands and dispersing north and west into the North Atlantic post-breeding from July onwards — has also been recorded on multiple Celtic Deep trips. Sooty Shearwater (Ardenna grisea) and Balearic Shearwater (Puffinus mauretanicus), the Critically Endangered Mediterranean endemic, have both been recorded on the pelagics; the Celtic Deep lies within the core UK waters for post-breeding Balearic Shearwater dispersal from July to October.

Skuas are a feature of the Celtic Deep in late summer and autumn. Great Skua (Stercorarius skua) — the most powerful of the four skua species, with its aggressive kleptoparasitic hunting of shearwaters and gannets — is regularly recorded, and Arctic Skua (S. parasiticus) is expected on most trips. Pomarine and Long-tailed Skuas are possible in optimal south or southwest wind conditions during the peak autumn passage window. The rare Roseate Tern (Sterna dougallii) — one of Europe's most threatened breeding seabirds, with the majority of UK breeding birds at Coquet Island in northeast England — has been recorded on the Celtic Deep pelagics, as has Black Tern (Chlidonias niger) on autumn passage. Northern Gannet (Morus bassanus), Northern Fulmar (Fulmarus glacialis), and Razorbill (Alca torda) are expected on every trip. Marine mammals are a consistent and spectacular bonus: Common Dolphin (Delphinus delphis) regularly accompanies the vessel in large, fast-moving groups, and Risso's Dolphin (Grampus griseus), Minke Whale (Balaenoptera acutorostrata), Fin Whale (B. physalus), Blue Shark (Prionace glauca), and Ocean Sunfish (Mola mola) have all been recorded on multiple occasions.

Dave Astins has been birding Pembrokeshire since 1988 and turned West Coast Birdwatching into a professional guiding business in 2018. His intimate knowledge of Pembrokeshire's seabirds — built across decades of watching at headlands including Strumble Head, St David's Head, and St Govan's Head, and from visiting the offshore islands — makes him an exceptional leader for these offshore excursions. Trips run from July to September with typically six or so dates per season; the peak window for Wilson's Storm-Petrel and Great Shearwater is late July through early September. Trips book out well in advance and demand exceeds availability in most years — all 2025 trips sold out before the season began. Book early via email or phone.