At a glance
Cemlyn Bay (LL67 0DS) is a North Wales Wildlife Trust reserve on north Anglesey — a brackish lagoon SSSI with one of Wales's most important tern breeding colonies (Sandwich, Arctic and Common terns). Free access. Limited roadside parking. Best visited May–July. Dogs on lead throughout nesting season. Bring binoculars.
About Cemlyn Bay
Cemlyn Bay sits on the north coast of Anglesey, a few miles west of the former nuclear power station at Wylfa — a juxtaposition that underlines the extraordinary ecological richness of the island's coastline, which coexists with industrial development in ways that would be impossible elsewhere. The bay's centrepiece is its brackish lagoon — a rare habitat type in Britain, maintained by a weir controlling the interchange between fresh water and sea, separated from the open sea by a natural shingle bank.
The shingle bank is where the terns breed. Each spring, Sandwich, Arctic and Common terns return from their winter quarters (Africa for Sandwich and Common; Antarctica for Arctic) to nest in dense colonies on the shingle. The Sandwich tern colony is among the most important in Wales, with several hundred pairs in good years. Watching a tern colony in full activity — the constant aerial movement, the fish deliveries, the calling and the spectacular diving — is one of the most rewarding wildlife spectacles the British coast offers.
The lagoon and surrounding habitat is designated as a Site of Special Scientific Interest for its tern colonies, its brackish water invertebrates and its botanical interest. The North Wales Wildlife Trust manages the site and maintains the viewing path along the shingle bank above the nesting area. The Anglesey Coastal Path passes through, connecting Cemlyn with Cemaes Bay to the east and the headlands to the west.
Wildlife watching tips
- Terns — Peak May–July. View from the shingle path above the nesting area — the colony is roped off. Binoculars essential.
- Wildfowl — Winter brings wigeon, teal, pochard and goldeneye to the lagoon. Goldeneye are particular highlights.
- Waders — Oystercatcher, redshank, dunlin and turnstone year-round on the bay margins.
- Raptors — Peregrine, marsh harrier and short-eared owl all recorded over the reserve.
- Nesting restrictions — Stay on the path and keep dogs on lead throughout the breeding season (April–August) to avoid disturbing nesting terns.
Visiting tips
Getting there
From the A5025 coast road, turn north at the signs for Cemlyn near Tregele village. Limited roadside parking at the end of the lane (LL67 0DS). Arrive early in summer — parking is very restricted. The coastal path from Cemaes Bay village (2 miles east) is an alternative approach on foot.
Facilities
There are no facilities at Cemlyn — no toilets, no café, no visitor centre. Bring everything you need. Cemaes village (2 miles) has a café, pub and toilets.
Find it on the map
Frequently asked questions
Cemlyn Bay supports breeding colonies of three tern species: Sandwich tern (the largest, with a harsh "kirrick" call), Arctic tern (which migrates from Antarctica — the longest migration of any bird), and Common tern. In recent years, the Sandwich tern colony at Cemlyn has been one of the most significant in Wales, with several hundred pairs nesting. A fourth species, Roseate tern (one of Britain's rarest breeding birds), occasionally nests or is recorded here.
Cemlyn Bay contains a brackish coastal lagoon — a rare habitat where fresh water and sea water mix, separated from the sea by a shingle bank. The lagoon is maintained by a weir that controls water levels. This brackish environment supports specialist invertebrates and aquatic plants, and is designated as a Site of Special Scientific Interest (SSSI). The shingle bank itself is the main nesting area for the terns.
The peak period for tern watching at Cemlyn is May to July, when the colonies are at their most active — nesting, incubating, feeding chicks and engaged in the spectacular aerial courtship and fishing behaviour that makes terns so fascinating to watch. The colonies begin to disperse in August. Binoculars are recommended — the nesting area is roped off to protect the birds and viewing is from the path above the shingle.
Beyond the terns, Cemlyn Bay is a productive birdwatching site throughout the year. In winter, the lagoon attracts wildfowl including wigeon, teal, pochard and goldeneye. Waders use the bay shores — oystercatcher, redshank, dunlin and turnstone are regular. Red-throated diver is occasionally seen offshore. In summer, hirundines, warblers and various gulls add to the birdwatching interest.
Cemlyn Bay is also scenically striking — the shingle bank and lagoon have an otherworldly quality, particularly in evening light with the dramatic headland of Wylfa to the east (site of a former nuclear power station, now in decommissioning). The north Anglesey coastline around Cemlyn is wild and largely undeveloped, with the Anglesey Coastal Path passing through. It is one of the quietest and most atmospheric stretches of the island's coast.