Arctic Tern

Irish Name: Geabhróg artach
Scientific name: Sterna paradisaea
Bird Family: Terns
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Conservation status

Status

Summer visitor from March to September to all Irish coasts. Winters off south Africa and as far south as Antarctica.

Identification

Usually seen over the sea. Slender seabird with narrow, pointed wings, long forked tail and long, pointed bill. Grey above and white below, dark cap to head. Flight light and buoyant, can hover briefly over the sea before diving in. Very similar to Common Tern (with which it breeds) and told apart by plumage and structure. Arctic tern is smaller, with a smaller head, neck and bill and slightly narrower wings, which look forwardly placed on the body. Very short legs. Adults have a blood red bill, usually with no dark tip. The underparts are greyer than Common Tern and there some contrast with the cheek. The wing pattern is useful in separation, Arctic terns shows no dark wedge in the primaries but shows a distinct trailing edge. Arctic terns have longer tail steamers, extending beyond the wing tips. Adult winter plumage, like all terns is different from breeding plumage, but is only seen in the wintering range. Also has distinctive juvenile plumage, with some brown in the mantle, a dark carpel bar and white secondaries. Shows a distinct trailing bar to the primaries, bill darkens rapidly.

Voice

Similar to Common Tern.

Diet

Marine fish, crustaceans and insects.

Breeding

Mainly a coastal breeding bird, but in Ireland the species also breeds inland on the fresh water lakes of Lough Corrib (Co. Galway) and Lough Conn (Co. Mayo). More colonies are found on the west coast with Co. Wexford, Co. Kerry, Co. Mayo and Co. Donegal having the largest number of birds

Wintering

Considered to have the longest migration of all birds, utilizing the summer of both hemispheres.

Monitored by

All-Ireland tern survey in 1995, and through breeding seabird surveys carried out every 15-20 years. Arctic Terns are also monitored annually at Rockabill and Lady’s Island Lake.

Blog posts about this bird

Arctic Tern

Rockablog: Eggs, eggs, and more eggs!

At the end of our last update, we mentioned that the terns had just begun landing on the island. Now, it's hard to imagine a time when they weren't here! While we've been very busy monitoring the island's changes, the terns have been even busier. Over the past two weeks, they have transitioned from cautiously inspecting potential nest sites to enthusiastically and vigilantly protecting their nests and eggs. We can confirm that all three species—common, Arctic, and Roseate Terns—are nesting on the island, with different pairs at various stages of nesting. Some terns have already begun incubating their full clutches of three-egg nests, while others are still selecting suitable areas to settle down. First, let's check in with each species of tern.  
  • Common Tern
Common Terns favor open nesting sites, resulting in our gardens, paths, and areas cleared of tree mallow being filled with their nests. Every morning, when we leave the keeper’s cottage to start work, we encounter new nests and eggs along the way to each study site. Common Terns are much bolder than the Roseate and Arctic terns and fearlessly protect their nests at all costs. The amount of guano (or seabird poop) on our hats and jackets increases tenfold when we survey the garden study areas as they are full of very defensive Common Terns protecting their eggs. We absolutely love to see it, as this behavior helps them defend against potential predators like Herring Gulls and Greater Black-backed Gulls.  

A full clutch of Common Tern eggs on Rockabill – May 2024 (photo taken under NPWS license).A full clutch of Common Tern eggs on Rockabill – May 2024 (photo taken under NPWS license).

Defensive common terns.Defensive Common Terns.

 
  • Roseate Tern
Roseate Terns are a fan of the deployed nest boxes, but that doesn’t mean that they exclusively nest there! We have seen some Roseate eggs in bizarre places so far, including on top of an occupied nest box! Aside from the nest boxes, they love nesting in vegetated areas meaning that the areas where we left rows of tree mallow are very popular with Roseate Tern pairs. Some of our study areas became occupied faster than others. In one study area to the south of the island, nearly all of the boxes are occupied by Roseate pairs, most of which have two, and sometimes three, eggs. Additionally, there are plenty of open nests around the nest boxes among the scurvy grass and vegetated areas. A breeding Roseate couple takes turns incubating the eggs and will continue to do so until they hatch. Occasionally, when a parent is relieved of their incubation duty and leaves the nest box, they stretch their wings and legs. I think all of us who have worked office shifts can relate to that! The incubation period of Roseate Terns is approximately 23 days, meaning that we will be expecting our first Roseate egg to hatch around Friday the 7th of June.

Roseate tern pair sitting on a nest box (photo taken under NPWS license).Roseate Tern pair sitting on a nest box (photo taken under NPWS license).

Roseate tern sitting on eggs in an open nest (photo taken under NPWS license).Roseate Tern sitting on eggs in an open nest (photo taken under NPWS license).

 
  • Arctic tern
While the island hosts fewer numbers of Arctic Terns compared to the Common and Roseate Terns, we are very happy to see that there 5 to 6 breeding pairs of Arctic Terns are nesting on Rockabill again this year. Compared the the Common Tern, the Arctic Tern is smaller, with a smaller head, neck, and bill, and slightly narrower wings that appear forwardly placed. These terns have very short legs and adults feature a blood-red bill, usually without a dark tip. Additionally, they have greyer underparts than the Common Tern, with some contrast at the cheek. We have confirmed the presence of 12 Arctic Terns and 5 Arctic nests so far.

Arctic tern among the scurvygrass.Arctic tern among the scurvygrass.

 

When we are not checking on the tern nests in our study sites, we are busy in ring reading. We are getting great use out of the 5 hides that we set up around the island. In the hides we can use the scopes and binoculars to read rings on as many birds as possible. By reading these rings we can gather information on the birds' origins, ages, nesting locations, mating patterns, changes in nesting success over time, and sometimes, their migration patterns when the same rings are spotted away from Rockabill.

We haven't forgotten about the other nesting seabirds spending the summer with us! Every day, we make sure to check on the Black Guillemot and Kittiwake breeding pairs, who have been just as busy as the terns, building nests and incubating eggs.

  • Black Guillemot

Most Black Guillemot pairs have already started incubating their eggs. Black Guillemot eggs are much larger than tern eggs and have a purple- blueish hue to them. We have been finding Black Guillemot eggs in the nest boxes that we deployed under the helideck and to the south of the island but we have also been finding plenty of eggs in dark cavities all over the island. Black Guillemot parents incubate their eggs for longer periods than terns, with both parents typically sharing incubation duties for 28 to 32 days.

Black guillemot on top of one of the 5 hides.Black Guillemot on top of one of the 5 hides.

Black guillemot egg in a wall cavity (photo taken under NPWS license).Black Guillemot egg in a wall cavity (photo taken under NPWS license).

  • Kittiwake
The Kittiwakes were the first seabirds to to greet us when we arrived on Rockabill. They have had a longer settling-in period than the terns and the Black Guillemots and took their time building up their nests, which are situated on the ledges of steep cliffs. The nests are bowl shaped and made up of seaweed, other marine vegetation, feathers, barnacles, and mud. Their nests were progressing gradually until one day, after a particularly stormy morning, the nests had progressed significantly! We spotted our first kittiwake egg on the 27th of May, nearly two weeks after our first Common Tern egg.

Kittiwakes on their nests (photo taken under NPWS license).Kittiwakes on their nests (photo taken under NPWS license).

   
  • What's Next? 
Before the eggs hatch we have a big task ahead of us. Next week, we will be joined by Project Manager Dr. Stephen Newton and will start this season’s big nest census. While us wardens have been keeping count of all of the nests in specific plots around the island, that still leaves thousands more nests around the rest of the island left to be counted. Once the nest census is complete, we will know how many breeding pairs, nests, and eggs, we have on the island. After that, it won't be long until the first egg hatches! This year’s work to protect and monitor the terns and other breeding seabirds on Rockabill would not be possible without the support from the National Parks and Wildlife Service and the cooperation of the Commissioners of Irish Lights. That's all until the next ternabout! We will be sure to check in again after the nest census is complete! -Emma, Rochelle, and Kyle
News

Rockablog: Preparing Rockabill Island for the 2024 season

Led by Project Manager Dr. Stephen Newton, the three Rockabill wardens have eagerly begun our NPWS-funded work on Rockabill and are very excited for what the season will bring. We have already been here for two weeks, and what a fortnight it has been! In just 14 days, Rockabill has transformed into a hub of seabird activity. The island has gotten progressively noisier, resonating with the calls of black Guillemots and Kittiwakes, and now, of Common Terns, Arctic Terns, and Roseate Terns.  Our days have been filled to the brim with preparations, ensuring that the island is primed and ready to accommodate the nesting needs of these birds.

Meet the Rockabill Wardens

three-people-on-rock-beside-lighthouse

Rockabill’s 2024 resident tern wardens- Emma (left), Kyle (middle), and Rochelle (right). 

Rochelle Streker This is Rochelle’s first season as a warden on Rockabill, having moved to Ireland from the United States last year. Rochelle has lots of seabird and conservation experience all across America, including working with and surveying Black Skimmers, Wilson’s Plovers, Red Knots, Newell’s Shearwaters, American Oystercatchers, Marbled Murrelets, Bald Eagles, and many different species of terns. She has also completed a master’s in wildlife biology from Clemson University on the reproductive ecology of Brown Pelicans in the northern Gulf of Mexico. As she settles into her new Irish life in Dublin, she is looking forward to learning more about Irish conservation and having a great season out on Rockabill! Emma Roberts Emma, a newcomer to the Rockabill warden team, holds a zoology degree from the University of Galway and is nearing completion of her PhD focused on urban red squirrel ecology. During her time in Galway, Emma volunteered with the Galway and Claddagh Swan Rescue and devoted her time to rescuing and rehabilitating, injured birds, including feral pigeons, Woodpigeons, Mute Swans, Herring Gulls, Black-headed Gulls, Mallards, Grey Herons, and the occasional Guillemot! Emma, an enthusiastic bird watcher with a particular affinity for seabirds, is very excited to learn more about seabird conservation and kickstart her career with a season on Rockabill. Kyle Coughlan Kyle is a Dublin native and studied for his B.Sc. in Zoology and M.Sc. in Evolutionary Biology at UCD and returned to Ireland in April after nearly seven years abroad. Following university studies, he spent a year working with in the south of France with a group focused on the conservation of the European Roller. Then he worked towards at Ph.D. at the Jagiellonian University in Krakow where he studied Great Tits and Blue Tits in the forests of northern Poland. Having recently submitted his thesis he is very much looking forward to spending his first summer on Rockabill with the terns.

Preparing the Island

After arriving at Rockabill on the 24th of April, the three of us and Steve quickly began preparing the island for the arrival of the Common, Roseate, and Arctic terns. Additionally, we've been observing the activity of the Black Guillemots and Kittiwakes that have already arrived on Rockabill and have begun searching for nesting sites. As the black guillemots are already on the island, we quickly began setting up nest boxes for them. These birds favour nesting in secluded, dark crevices within rocky formations. So far, we have set up black guillemot nest boxes beneath the Helipad, a preferred nesting spot for these birds, and on the rocks to the north of the island where we've observed pairs congregating. guillemots-on-rocks-beside-sea-evening guillemots-under-helipad-beside-sea

Black Guillemot pairs checking out the nest boxes on the rocks to the north of the island (top) and under the helipad (bottom).

The main island is called the “Rock” and the smaller rocky island is called the “Bill”. While the Bill has very little vegetation, the Rock is covered in a densely growing plant called tree mallow. It takes up so much of the ground area on the island that there is no room for common, arctic, and roseate tern nests. Its swift removal was our next port of call. First, we removed the tree mallow from our study sites and then went about removing it from the remainder of the main island. We also had to organise our nest boxes for the Roseate Terns. The nest boxes were taken out of storage and organised by number from 00 to 948! Some of the boxes were broken or damaged during the last breeding season, so these boxes were repaired if feasible. Additionally, new boxes were constructed and labelled with ID numbers to fill any gaps. With a considerable number of nest boxes on hand, our aim is to maximize nesting opportunities for the roseate terns by deploying as many boxes as we can. numbered-tern-boxes-stacked-against-wall

Roseate Tern nest boxes.

Next came the 5 hides, which are required to monitor the nesting terns without disturbing them. We assembled the hides at vantage points across the island. They were then weighed down with heavy rocks and tied down with rope in order to prevent them from being blown away in any storms. Luckily, we got the hides set up and secured in time for our first stormy day! bird-hide-rockabill bird-hide-by-sea-rockabill-island

2 of the 5 hides set up around the main island.

On Saturday the 27th of April, we were visited by the Geological Society of Ireland, who spent a few hours on the island looking at Rockabill Granite. The members of the GSI were kind enough to help us remove tree mallow from various study sites. We really appreciated having more hands to help us with the removal! When the GSI left that evening, Steve joined them and headed back to the mainland. With Steve’s departure us wardens got busy setting up all of the Roseate Tern nest boxes around the island. First, we set up boxes around each of the assigned study sites, which can be monitored from the hides. Next, we started setting up the remainder of the nest boxes around the island. Aside from two stormy days with strong winds, rain, and high waves, we have been very lucky with the weather. A succession of clear days allowed us to finish setting up all of the nest boxes. Just in the nick of time too because this week- the terns arrived! First, the terns started circling the lighthouse in the AM. Every day they began flying lower and lower to the ground. Now, plenty of them have started landing on the island and looking for places to nest. We have spotted all 3 species of tern so far; Common Terns, Roseate Terns, and Arctic Terns. With their arrival, the island has gotten progressively noisier. We are very excited for them to start nesting so that we can continue to monitor them and start ring reading. And there you have it! Stay tuned for more updates as we navigate through the season's tern of events. - Emma, Rochelle, and Kyle This year’s work to protect and monitor the terns and other breeding seabirds on Rockabill would not be possible without the support from the National Parks and Wildlife Service and the cooperation of the Commissioners of Irish Lights.  

Similar Species

Common Tern

Irish Name:
Geabhróg
Scientific name:
Sterna hirundo
Bird Family:
Terns

Roseate Tern

Irish Name:
Geabhróg rósach
Scientific name:
Sterna dougallii
Bird Family:
Terns