A Fly on the Wall Look at the Dublin Port Tern Colony

Due to tern chick predation by a mystery predator, we deployed a motion-triggered “trail camera” in an effort to identify the visiting culprit. 

When we retrieved the memory card some days later, we were disappointed not to have identified the predator, but we did capture an intriguing insight into the activities and routines of the terns when completely undisturbed on the colony. 

In the three days, the camera was triggered 2,088 times, and after meticulously scrutinising each photo, we discovered that the platform is not just home to terns at this time of the year. 

Nocturnal squatters started to appear around 8 pm each evening and stayed overnight, roosting on the boundary planks and within the nesting compartments until shortly after 5 am each morning. Although the camera was directed into just one nesting compartment, it was clear from the sequence of photos that Starlings use the structure as a night time communal roost with very little, if any, reaction from the nesting terns.

Adult and juvenile Starlings get some sleep among the nesting terns
Ricky Whelan

The early bird gets the....sand eel (bird centre foreground) Ricky Whelan

We also managed to make some observations on the hours that the terns keep. They became active between 4 and 4:30 am each day, and the earliest food delivery occurred at 5:19 am. As expected, the adults spent their day diligently coming and going with food, resting and occasionally brooding young chicks and eggs. Sporadically, the terns do what’s known as a “dread.” Dreading is when the entire tern colony suddenly and silently (unusually for terns!) takes to the air and vacates the nesting area and performs a few looping laps of the nesting site, before returning to business as usual. Dreads are pretty much over as soon as they start, and in general, last less than about 10 seconds. This behaviour is associated with the terns being startled by an avian predator, but often occurs with no apparent stimulus.

Dreading adult terns leave the nesting colony briefly Ricky Whelan

Peace at last. Common Tern chicks and adults roosting for the night

 with Starlings tucked in along the left hand edge Ricky Whelan

As the light fades, the frequency of prey deliveries declines and everyone is settled down for the night by about 10 pm. 

So, while we didn't manage to get confirmation on the mystery predator, (which we suspect is Mink or Rat), we did get some interesting insights into the tern activity on the platforms when they are left to their own devices. The effect that this predation has had on the overall colony success this season has yet to be measured, but will be quantified by the end of the season.

Tern Talk

School’s out, but we’ve still got plenty of work to do. As the seasons pass, we see huge differences in the composition of the birdlife in Dublin Bay. And new arrivals mean different survey types to adequately determine how they are all doing. Tern time is always a very busy time for us… which may explain the lack of blog posts recently! 

Many of the waders and wildfowl are now long gone, with only a fraction of their winter numbers remaining. Last February, we had a total of 38,854 waterbirds in Dublin Bay during a low tide survey. The corresponding number in June was just 3,566. But that doesn’t mean that Dublin Bay is not important for waterbirds in the summer -far from it, in fact, but that’s for another post!

But it’s tern time for us now, and it will be until around about the time that the kids go back to school and the terns go back to Africa (and beyond). So, right now, we’re flat out doing nest censuses, ringing and colour-ringing chicks and assessing foraging locations within Dublin Bay. And before too long, we’ll be assessing the numbers of post-breeding terns roosting on Sandymount Stand in late August and early September. At which point, the waders will be flying in and the wildfowl won’t be too far behind them. So, it’s always worth taking the time to enjoy the breeding season before it passes...

Common Terns  Niall Tierney

Arctic Tern nest at the foot of a mooring bollard Niall Tierney

Arctic Tern nest Niall Tierney

Arctic Tern nest Niall Tierney

Arctic Tern nest Niall Tierney

Erythristic Arctic Tern eggs Niall Tierney

Common Tern nest Niall Tierney

Common Tern nest Niall Tierney 

Newly hatched Common Tern Niall Tierney

Common Tern chick Niall Tierney

Common Tern chicks Niall Tierney

All photos taken under NPWS licence. 

Spring Break

Bird life in Dublin Bay certainly has changed to reflect the coming and passing of spring. As we discussed in our two preceding blogs many of our familiar species have headed north in an effort to mate and hopefully successfully breed at their respective breeding grounds. For the most part it's business as usual for the Dublin Bay Birds Project Team. We continue our monthly suite of waterbird counts and have seen increasing numbers of terns return to the bay in anticipation of their breeding season ahead. A new tern-breeding raft has been installed north of the Great South Wall in the past month and we will keep a close eye on the "take up" of breeding pairs on the raft as the season develops.

Last week our own Niall Tierney took the opportunity to visit Iceland for a short holiday. Showing true commitment to the project he has spent much of his time in Iceland combing the coastlines' fjords and bays for project-ringed birds. Lo and behold he has connected with one of our birds previously caught and ringed at Sandymount Strand as part of our project work last February.

Oystercatcher "FL" foraging last week on the Icelandic coast - Niall Tierney

Word has reached us of two sightings the Oystercatcher "FL"(the birds individual code) on the 6th and 16th of May at Hvalfjordur which is located on the south western side of the Icelandic coast. Niall reports "FL" has been with a non-breeding flock of c140 oystercatchers frequenting the area. It must have been a great experience for Niall to have caught and possibly even personally ringed FL in Dublin last February (HEREs the blog from that catch day) and then see it in Iceland where it has returned in an attempt to find a mate and raise young this spring. We look forward to hear more details from Niall in the coming days. 

Oystercatcher "FL" re-sighted at Hvalfjordur Iceland

Standby for more re-sighting stories as the season develops and for news on the breeding tern season ahead.

BirdWatch Ireland is currently running a campaign (along side other EU Birdlife partners) in an effort to stop the European Commission from reopening and making negative changes to two EU Directives. The strength of the EU Habitats Directive and The Birds Directive is under threat. These laws are incorporated into Irish law and are the vital in protecting the habitats and species of Dublin Bay and throughout the rest of Ireland and Europe. Please follow the link HERE and take a few minutes to help this campaign.

April Fowl

As spring is (almost) turning to summer, there is also a transformation in the bird life of Dublin Bay. Having spent the winter taking bi-monthly counts of the birds at Bull Island, I have watched the birds in the lagoon shift with the seasons. Not only are new species arriving and others heading off around the world, but the appearance and behaviour of certain species is adjusting to the warmer season.

The difference most apparent to me were birds coming into their colourful summer plumage, which is generally much more striking and attractive than winter plumage (and makes identifying species at distance a much faster task!). Many of the Black-tailed Godwit have already traded their plain brown winter plumage for vibrant rufous-orange on the neck and black barring on the breast. Similarly, Dunlin become a rich chestnut with a prominent black belly patch, rather than their wintertime grey-brown. The Black-headed Gulls finally live up to their name and develop a striking chocolate-brown head for the breeding season. This emergence of birds in full breeding plumage signals the birdy courtship season is in full swing and summer is truly on its way!

Black-tailed Godwit in breeding plumage (Andrew Kelly)

 Black-headed Gull living up to its name (Oran O’Sullivan)

Dunlin in summer colours (Ken Kinsella)

The change is not only in appearance but also, of course, in behaviour. As their migration departure is approaching fast, the Brent Geese at Bull Island are frantically building stores to see them through the journey. Since they have spent the winter gorging all the eelgrass and algae in sight, by spring Brent Geese must look for something new to devour. In the last month I have observed more geese feeding in the grass around the lagoon instead of the intertidal zone within the lagoon. Early in winter, the geese feed on eelgrass and algae at low tide, but when all of it has been eaten away, they begin to graze grassland. This reflects how the change in vegetation through the seasons influences the bird life, as some sources become depleted and others are made available.

Perhaps the most significant change through the seasons is inward and outward migration to and from Dublin Bay. By late April, most of the over-wintering species have left Ireland and summer species are arriving. I have noticed a reduction in wintering species’ population numbers at Bull Island during April counts, as migration to their summer grounds gets underway. Smaller numbers of Sanderling, Knot and Turnstone meander around the lagoon, while Wigeon and Teal in particular have disappeared off my radar. But the upside to the absence of these birds are the arrival of summertime species to Bull Island. I spotted my first two Sandwich Terns of the season pottering around the lagoon just last week - something that screams “summer is here!!” in my face.       

While my bird counts at Bull Island are finished for this winter season, the spring transformation is set to continue. More summer species, such as the remaining Terns, will arrive, and those Brent Geese inhaling the grass will abscond to Canada. Hopefully this summer will be a kind one to our breeding birds and next winter’s monthly counts will show positive results!

Susan Doyle

March: In like a lion, out like a lamb…or did we get that backwards?

We have seen the end of March, and Spring is in full swing throughout Dublin Bay. Our schedule of bi-monthly surveys have allowed us to see all the changes that happen across the month, and at this time of year, Dublin Bay becomes an airport terminal, with passengers arriving a departing from far and wide.

In the past few weeks, bird numbers throughout the bay have been steadily decreasing, as waterfowl, waders and gulls take flights to their breeding grounds. The Teal will end up in Iceland, northern Europe and Russia; the Knot will head for Greenland and Canada, after staging in Iceland or Norway; and the Black-headed Gulls will spread out again right across northern Europe.

On the ground, the sound of wee-oo-ing Wigeon is replaced by the coor-eee of Whimbrel passing through on their way northwards having wintered on the West African coast. On Bull Island, singing Skylarks nearly drown everything else out, but what a welcome sound it is. And there has been a Meadow Pipit singing his heart out over the spit at Merrion gates too.

These days, the project team open our inboxes each morning in anticipation of getting emails from northern climes, bringing news of Dublin-ringed Oystercatchers, Redshanks and Bar-tailed Godwits en route to, or on, their breeding grounds. Last week, we heard from Ian Durston from Nairn in Scotland who has one of our birds breeding in the field next to his house. XI has taken up residence in a stubble field in Cawdor, Nairn and seems to have paired up, so it may not be too long before he hears the pitter-patter of tiny …cockle-stabbers.

XI and mate in Nairn, Scotland Ian Durston

The Brent Geese are preparing for their imminent departure, before re-fuelling in Iceland, crossing the Greenland Icecap and finally arriving in Artic Canada. Soon there won't be sight nor sound of them until they return in September. But now we're on standby for the arrival of the breeding terns. Sandwich Terns tend to take an earlier flight than the rest, and handfuls have been seen already, but it’s the Common and Arctic Terns that we’re waiting for. Their harsh and rasping screechy calls will herald the onset of summer fieldwork, and trips to the Port to ring the chicks and monitor the breeding success of the colony. 

So, there's plenty to see in Dublin Bay - it's an ideal time of year to get out and see migration for yourself, to observe the comings and goings of spring. 

Ecologists strike it lucky!

BirdWatch Ireland’s waterbird ecologists working on the Dublin Bay Birds project spend a lot of time on Sandymount Strand and have struck it lucky with a remarkable discovery.

A sea-front curtain-twitcher remarked:

“They seem to be here all the time! I’ve seen them here at all hours of the day and night – with their telescopes watching the birds, catching them and marking them with plastic leg rings, or even tracking the Oystercatchers with radio-antennas, so it’s little wonder that they were the ones to find the gold.”

“When I saw the low rainbows, I started to think about their significance,” said one of the project team, who also has a keen interest in Irish folklore. “My grandfather comes from Slieve-an-ore [Gold Mountain], near Feakle in Clare. He has seen the low rainbows there too, and told me what they mean. Tales of leprechauns and pots of gold are not just bedtime stories, despite what people may think.”

Squally showers on Sandymount Strand Niall Tierney

The ecologist continued:

“We managed to get some spades and sieves from colleagues in nearby UCD and got straight to work. It’s not rocket-science – it’s simply a matter of scouring the sandflats looking for signs of mineralisation, and then getting busy with our spades and sieves. The gold pellets are pretty obvious, once you get your eye in.”

Sifting through the sediment Niall Tierney

Others have suggested that the gold may originate from one of the many shipwrecks in Dublin Bay and that it may just be washing up now, after the storm force gales of Monday night. The steamship RMS Leinster, which was torpedoed by a German U-boat UB-123 on the 10^th October, 1918, is emerging as the prime candidate, as military historians have long speculated on the likelihood that she was carrying a significant cargo of gold.

Whatever the source of the gold, it’s expected that, much like the infamous 19^th century gold rushes, people will flock to the Dublin coast aspiring to make their fortunes.

Susan and Helen make their way back with their loot Niall Tierney

BirdWatch Ireland has remained tight-lipped about how it will spend its windfall. However, a source close to Ireland’s largest nature conservation organisation suggested that the money will either be spent on an ambitious plan to create the world‘s largest aviary by roofing Co. Wicklow, or on a Passenger Pigeon re-introduction project, which aims to solve the world’s hunger crisis. 

Coláiste Íosagáin meets Dublin Bay's birds

We were delighted to have the opportunity to meet with the students and teachers from Coláiste Íosagáin, Booterstown recently. The outing was part of the science curriculum focusing on local biodiversity and habitats, so it was an excellent opportunity to spread the word about our research on the waterbirds in Dublin Bay and the habitats upon which they rely. 

Ricky meets with Coláiste Íosagáin students
 at Booterstown Marsh Neasa Ní Ghallchóir

On the day, three 2nd year classes visited Booterstown Marsh and identified the ducks and waders feeding in the nature reserve. Later we visited Sandymount Strand to see some of the birds that prefer to feed on the sandflats and along the tideline.

We also did some radio-tracking, which proved a big hit! We’re currently tracking ten Oystercatchers to work out their foraging and roosting habitats during the day and at night, and with the girls’ help, we were able to get a few more fixes for the database. 

Getting a closer look at some Redshanks 
Neasa Ní Ghallchóir

We all got a chance to see a great variety of waterbirds on the day; everything from the vegetarian, grazing Brent Geese to the carnivorous, probing Dunlin, and learned all about their adaptations and foraging strategies. Other topics covered included disturbance, migration, population trends and conservation issues.

The girls have a go at radio-tracking 
Oystercatchers Neasa Ní Ghallchóir

A big thanks to all the students and teachers for an enjoyable morning chatting about the importance of Dublin Bay for birds and biodiversity. It was heartening to meet students who were both interested and well-informed about the natural environment around them. I wonder if the children at our Oystercatchers’ breeding grounds are as well informed. …Maybe we’ll have to plan a trip to Iceland, the Faroe Islands, Norway or Scotland to find out! ;-)