As the first terns arrived, we had time to learn the rhythms of the site – surveying black-headed gulls, oystercatchers, and lingering golden plovers, while learning about lagoon monitoring and managing the weir during dramatic spring tides. 

As the first Sandwich terns arrived, their calls joined the air already filled with the constant calls of black-headed Gulls, whose energy brought life to blustery mornings and storm-lashed days. Among them, the more elusive Mediterranean gulls began to appear –subtle at first, but soon unmistakable with their jet-black heads, deep red bills, and softer, purring calls

As the weeks passed, numbers increased – as did the temperature! Up to 19 Mediterranean gulls were recorded, and initially it looked like up to nine pairs, but by mid-June it was apparent that only four pairs had successful hatched young. Their behaviour – pairing, nesting, and even occasional hybridisation with black-headed gulls  – offered a fascinating glimpse into the complexity of colony life. Both species play a vital role here, acting as vigilant defenders against predators, especially herring gulls, and contributing to the noisy daily interactions around the islands. 

By June, the Sandwich terns dominated the islands, creating a noisy, chaotic soundscape. We estimated over 1,600 pairs were nesting and by early July the young were very apparent around the islands. Monitoring their movements became a daily priority, alongside engaging visitors and sharing the story of this remarkable place. Checking for signs of avian flu remained important, with simple actions, like cleaning footwear, helping to protect these vulnerable populations. 

Smaller numbers of common and Arctic terns were also present on the islands, and provided a unique chance for our visitors to compare the three species – often in one telescope view! Roseate terns have been regularly seen but despite promising signs of courtship behavior, we don’t think there was a breeding attempt. 

At the heart of this bustling seabird colony lies a much smaller but equally vital species: the sandeel. These slender fish form the backbone of the marine food web, providing essential nourishment for Sandwich terns and the other tern species at Cemlyn. Their abundance – or absence – can ripple through the entire ecosystem. 

Together, the birds of Cemlyn act as sentinels of the sea. Their presence reflects the health of the wider environment, from the smallest fish to the vast marine systems beyond. Through careful monitoring, conservation work, and public engagement, the wardens play a key role in safeguarding this special place.

A key part of this work is our involvement with a UK-wide ringing and flagging project for Sandwich terns. Recently, we worked with licensed ringers to put special ’flags‘ on over 100 Sandwich tern chicks.  Over several years, these efforts have revealed a fascinating insight into the terns' movements.  Late summer re-sightings of fledged and flagged birds come from along the North Wales coast and further north to Scotland. Fro birds flagged in previous years, there have been sightings from Spain, and even further afield, from Gambia. 

So, if you’re out birdwatching along the North Wales coast in the next few weeks, please look out for our terns and their flags (orange with three black letters – as shown in the photo)!  Do let us know where you see them and, if possible, which ring codes you see.  It's great to be able to keep track of our colony and we can all work together to do it – citizen science in action. Send the details to cemlynwardens@northwaleswildlifetrust.org.uk