Irish Name: Saidhbhéar
Scientific name: Rissa tridactyla
Bird Family: White-headed Gulls
Conservation status


Summer visitor to steep coastal cliffs along all Irish coasts. Disperses to the open ocean in winter and less frequently seen.


A small gull, slightly larger than Black-headed Gull, which is basically grey above and white below. Adults are easily told apart from other gull species by the solid black wing tips, showing no 'mirrors' (white at the wing tip), and two toned grey upperwing. Adult birds have a yellow bill and dark legs. Adults show white heads in the summer and a dark patch behind the eye in the winter. Juvenile and first year birds have a bold dark 'W-pattern' across the wing and a dark tail band, although these features can be much faded by the first summer/second winter. Second year birds are similar to adult birds but can show black fringes to outer primaries, black on the bill or winter head patterning in the summer months.


Noisy at colonies, giving a nasal call resembling its name. Can often be heard clearly over the sounds of other birds at seabird colonies.


Fish, waste from commercial fishing and invertebrates.


Forms colonies, sometimes thousands strong, often with other seabirds. Breeds on steep sea cliffs where it builds a nesting platform on the most vertical and sometimes improbably steep areas. Will occasionally use man-made structures such as old buildings, for example in Dunmore East, Co. Waterford.


Winters at sea.

Monitored by

Breeding seabirds are monitored through surveys carried out every 15-20 years, the last was Seabird 2000, which was undertaken between 1998 & 2002.

Blog posts about this bird


Rockablog - Ringing Blitz Bonanza!

It has been an exciting time on Rockabill with the annual ringing blitz taking place during the first week of July. The three wardens were joined by BirdWatch Ireland staff and experienced ringers Dr. Steve Newton and Brian Burke. Enna O’Conner also joined us a volunteer and proved an extraordinarily efficient scribe! The goal of the ringing blitz is to ring every single one of the Tern chicks on the Island in about two days. By giving all of the chicks a tiny, uniquely-coded leg ring, it means we can continue to learn about them through their lifetime. Do chicks hatched on Rockabill come back here to nest? Do they go to other colonies? What age are birds in the Rockabill colony? Do they pair with birds of a similar age? Do younger or older birds have better breeding success? And of course, they might get seen or caught on migration too, helping to confirm migration patterns and help fill in gaps in our knowledge. For the bird, wearing a leg ring is like a person wearing a watch - after you first put it on you forget it's even there. Bird ringing is strictly licensed in Ireland through both the NPWS and BTO and requires extensive training before licenses are granted!  
Roseate Tern adult - note the leg rings, which allow us to keep learning from these birds throughout their lifetime. (B. Burke, photo taken under NPWS license).
  The process starts by lining up and sweeping through each subcolony, picking up as many chicks as possible as the team moves through the area. The smaller birds are easy to catch as they freeze or try to hide under leaves or rocks, but the larger, braver chicks often make dash for safety. A person is needed on each side to 'herd' the chicks for an easier catch. Once caught, Enna gave the ringer a uniquely coded ring and recorded the species, location, wing size and other important details while others ringed the chick, placed it back in its original setting and moved on with our grid searching. It proved to be a very busy few days!
Roseate (left, right) and Common Tern (middle) chicks trying to hide as the wardens approach! (K. Owens, photos taken under NPWS license)
  In total 146 Common Tern chicks and 619 Roseate Tern Chicks were ringed in the two day period. This is much lower than most years, and we'll get into that in a future blog... Following the blitz it is the wardens job to find any other chicks that don’t have rings and ring them as needed. Some will have been missed during the original blitz, and others will have hatched in the weeks since. The wardens will sweep the entire island a couple more times and also pick up chicks as they are walking through, working or ring reading in the colony. They are still finding chicks to ring today as the late nest chicks are hatching and growing.
Kittiwake chicks on Rockabill - most are well grown now and are sporting new leg rings! (K. Owens, photos taken under NPWS license)
  In the following weeks after the Tern-ringing blitz, project manager Steve returned to Rockabill to ring the Kittiwake and Guillemot chicks with the help of the wardens. There are much fewer of these chicks but they are however a bit more difficult to get to! Staff were climbing up and down rock faces and putting their arms in long dark holes to retrieve these birds out of their nests. A total of 94 Kittiwake chicks and 72 Black Guillemot chicks were ringed this year.
Warden George, carefully accessing some Kittiwake nests on the cliff in order to ring the chicks (K. Owens)
Ringing Black Guillemot chicks on Rockabill (K. Owens, photos taken under NPWS license)
  Now that almost all the chicks on the island are ringed and starting to fly it is nearing time to pack up and leave. The wardens have started bringing in nesting boxes to clean and store for next season. There is also a lot of data collation and report writing going on, it is nice to see the chicks start to fly but sad to see the absence of young chicks around. Stay tuned for the next blog which will be the last one of the season!  

 - Kristy & the Rockabill team

  (PS - Don't forget to keep an eye out for terns roosting around the coast at this time of year, and let us know! See here for more)

This year's work to protect and monitor the terns and other breeding seabirds on Rockabill would not be possible without the Roseate Tern EU LIFE project, support from the National Parks and Wildlife Service and the cooperation of the Commissioners of Irish Lights.

To revisit news and blogs from previous years on Rockabill, click the link here.


Rockablog - How many nests?

That’s the big question every year on Rockabill. “How many nests did you find this season?” Knowing how many breeding pairs we have on Rockabill, and how that compares to other colonies and to previous years,  is a very important question to answer. A few weeks ago, the wardens were joined by BirdWatch Ireland's Senior Seabird Conservation Officer Dr. Steven Newton to start this season’s big nest census. While the wardens have been keeping count of all of the nests in their study areas in specific plots around the island, that still leaves thousands more nests around the rest of the island left to be counted. We had a big job ahead of us!  
Hundreds of Roseate Tern nestboxes on Rockabill (E. Tiernan, photo taken under NPWS license)
  The nest census is always a busy couple of days, tackling one part of the island at a time in a methodical way. Every Roseate Ten nestbox was checked for eggs and all open Roseate Tern nests (ie. nests outside of boxes) and Common Tern nests were marked with a coloured peg with a numbered code for each.  
A single Roseate Tern egg, nest marked with a coded clothes peg! (E. Tiernan, photo taken under NPWS license)
Common Tern nest with two eggs, marked with a peg. Note the rounder shape and bigger spots compared to the Roseate Tern egg above (E. Tiernan, photo taken under NPWS license)
A Roseate Tern egg in one of the hundreds of nestboxes on Rockabill Island (E. Tiernan, photo taken under NPWS license)


This season had 1,624 breeding pairs of Roseate Terns. This is a good increase of 60 pairs from last year  and is the second highest on record for Rockabill, beaten only by 2018 which had 1642 pairs.  
Roseate Tern nesting on Rockabill Island (E. Tiernan, photo taken under NPWS license)
  While this is wonderful news for our Roseate Tern population, the Common Terns are not doing as well. This season we found 1,753 pairs of Common Terns, down 80 from 2019 (1,833 pairs) and down 285 from 2018 (2,038 pairs). There could be several reasons for this decline in Common Tern numbers, including some poor breeding seasons in the last 5 or 6 years as well as 'density-dependent' factors. This means, simply, that having higher densities of the same birds in a single location can cause different problems, including pressure on birds because of competition for food, with parents having to travel further to feed themselves and their chicks as a result. There's extra competition for nesting space too, so some younger Common Terns might decide to nest at other colonies rather than come back to the jam-packed Rockabill colony. Hopefully that will benefit nearby colonies such as Dalkey Island and Dublin Port, as well colonies further afield in Wexford, Northern Ireland and even Wales. Ultimately, the more strong Tern colonies we have in the Irish Sea and further afield the better, so a decline at one colony should be looked at in the context of what's going on in the wider environment. This ethos is at the heart of the recent EU Roseate Tern LIFE project - to create and restore a network of Roseate Tern colonies in Ireland and the UK.  
Common Tern and chick on Rockabill Island (E. Tiernan, photo taken under NPWS license)
  In addition we recorded 41 pairs of Arctic Terns, but as in previous seasons they're sttruggling to successfully raise chicks, largely due to predation. We haven't yet noticed an influx of Arctic Terns from the recently-abandoned Welsh colony, but we're keeping our eyes peeled! arctic-tern-in-flight
Arctic Tern (K. Murphy)
  It's not just the Tern nests we're counting during the nest census. We also recorded a total of 173 pairs of Kittiwakes and 62 pairs of Black Guillemot. Those Kittiwake numbers are pretty good, though only around 72 of those have successfully produced chicks so far. The Black Guillemot count is a bit lower than we'd have hoped, and their numbers have fluctuated between 50 and 100 pairs for several years now, with winter weather one of the big factors influencing their survival.
Kittiwake and chicks, nesting on Rockabill (B. Burke, photo taken under NPWS license)
  And finally... We have been nominated for a Natura2000 Award!  You can vote for us via the link below. Look for the title “Cooperation across seas: Roseate Tern colony networking.”


That’s all from us on the Rock for now but there is a lot more still to come!

Emma and the Rockabill team


This year's work to protect and monitor the terns and other breeding seabirds on Rockabill would not be possible without the Roseate Tern EU LIFE project, support from the National Parks and Wildlife Service and the cooperation of the Commissioners of Irish Lights.

To revisit news and blogs from previous years on Rockabill, click the link here.

Similar Species

Black-headed Gull

Irish Name:
Scientific name:
Larus ridibundus
Bird Family:
Hooded Gulls