Breeding terns update

The main tern nest census was carried out on a fine day last week, and showed good increases in the number of nests and clutch sizes since our last visit.

As we rowed out to the platform, we could see that something was distressing the terns – they were repeatedly diving at an unseen intruder towards the eastern end of the platform – and we immediately suspected a pillaging corvid. We climbed the ladder to the platform and carefully picked our way (tern eggs are almost invisible on the shingle substrate) to the eastern end to find a Kittiwake spread-eagled across one of the nests. A quick examination revealed that the bird was very freshly dead, but showed no signs of external injury. Whatever the cause of death, this bird picked a less than peaceful refuge for its final moments... 

Common Tern nest in Dublin Port. Niall Tierney. 

Anyway, we promptly got back to the job in hand – the nest census. This is simply a count of the number of nests and the number of eggs per nest. This, along with the estimation of the number of adult birds present, allows us to see how the colony is faring from year to year. On the main platform, 418 Common Tern nests were recorded, with clutch sizes ranging between 1 and 4. There were 25 Arctic Tern nests, with clutch sizes of 1-2. There was an increase in the number of cached depredated egg shells, indicating that the (still unidentified) avian predator had been on the platform since the earlier visit (see previous post).

Two Arctic Tern nests in Dublin Port. Niall Tierney.

Once the census was complete, we quickly vacated the platform to allow the adults to resume incubation. Peak hatching is expected to be around the turn of the month. We’ll check back in on the colony again in the coming weeks to monitor breeding success and will post another update then. 

Breeding Terns in Dublin Port

Dublin Port has been home to a colony of breeding terns since at least 1949, and in recent years, has supported 550 and 55 pairs of Common and Arctic Terns, respectively. The monitoring programme that was started by the late Oscar Merne in 1995 will be continued by BirdWatch Ireland this year, and in subsequent years.

Tern platform in Dublin Port. Richard Nairn

Although the cold spring has resulted in delayed commencement of breeding for lots of birds, the Common and Arctic Terns in Dublin Port are now nesting. Last week’s colony census recorded 263 Common Tern and 8 Arctic Tern nests. Worryingly, a cache of at least 23 tern egg shells was found on one of the platforms, with the culprit most likely a corvid. 

Depredated tern eggs cached on the platform. Richard Nairn

As the colony reaches it full strength, it’s likely that the full complement of terns will be sufficient to drive off any intruders. As someone who has ringed in tern colonies, I can tell you that hundreds of angry terns have no trouble making their feelings known...

The joys of tern fieldwork!

Summering waders

Sandymount strand was chock-a-block with joggers, walkers and dogs on Sunday morning, but they weren't the only ones taking advantage of what Sandymount Strand has to offer. As soon as I pulled up, I noticed a flock of ‘smalls,’ (i.e. unidentified Dunlin-sized waders) pinging around between the joggers and dogs. A glimpse of some black bellies allowed me to confirm that they were mostly smart-looking, summer plumaged Dunlin, but there were some Ringed Plover tagging along too. A quick scan with the scope through the heat haze produced 109 Oystercatchers distributed in several aggregations and a flock of 154 Bar-tailed Godwits on the tide line further south, towards Booterstown Station.

To be honest, I was surprised to see so many waders still hanging around on the beach. I don’t usually give too much thought to waders outside the September to March I-WeBS season. I suppose it just goes to show how important year-round counts are at a site like Dublin Bay.

Sunny Sandymount Strand

The ring-reading conditions were perfect: pleasant temperature, good sunshine and a backing track of Swallows and Common Terns chattering and squabbling overhead. I managed to read twelve rings, but there were 5 or 6 that I just couldn't get....something ‘J’... or was that something ‘I’... No, definitely an ‘L’...but what’s the first letter? Get out of that puddle and let me see it!

Thanks again to those of you who have been diligently sending in ring re-sightings. We’re slowly putting this story together, but new ring readers are always welcome to contribute to this worthwhile research. No need for flasks or hats or gloves - just grab the scope and the notebook and get out there! 

Arctic Terns – extraordinary migrants

As you know, we have put colour rings on a number of Oystercatchers to allow them to tell us a story about their movements around Dublin Bay and beyond, and we intend to do some hi-tech tracking work in the coming years too. Who knows what story this work will tell?

...But if birds could actually tell stories, what would they say?

Terns arrive!

Since St Patrick’s Day, Sandwich Terns have been reported along the Co. Dublin coast. These have been supplemented by reports of small numbers of Common, Arctic and Little Terns from about the start of April onwards. My own first summer migrants of the year were two Sandwich Terns on the Merrion Gates spit on the 28^th March. This BirdTrack graph shows that Sandwich Terns’ arrival hasn’t been affected by the prolonged period of easterly winds and the cold temperatures that played havoc with this year’s spring migration schedule.

The percentage of birders' list in Britain and Ireland
that include Sandwich Tern. Source: BirdTrack.net

Despite the slow start, the delayed hirundines and warblers have been flooding in recently.  The rest of the terns will join us shortly, and it won’t be long before the tern colonies in Dublin Port, Rockabill and Dalkey Island are once again in full swing! 

Changing of the guard....

Signs of the changing seasons have been evident in Dublin Bay over the past few weeks, even if we had to wait a bit longer for the corresponding change in temperature! The wader numbers continue to fall, as most head off to breed in more northerly areas, and the terns are starting to arrive to take their place.

Despite the decreasing numbers, re-sightings of the marked birds continue to come in. Seven colour-ringed birds were reported in a flock of about 100 at the north end of Sandymount Strand on the 19^th April. Unfortunately, they were disturbed by dog and flew off before the inscriptions could be read, but the information is useful all the same. In the same area on the 25^th April, four more inscriptions were read from a small foraging flock. Another one of our birds was seen on Dalkey Island on the 23^rd April. It seemed to be paired to another bird and was apparently prospecting for a nest site. 

These reports bring us up to 160 re-sightings of 87 individual birds, which really is fantastic progress in such a short time! A sincere thanks to all those who are taking the time to put in some ring-reading effort to help us piece this story together.

Dublin Bay Godwit drops by Scotland

A flock of Black-tailed Godwits, that spent the winter 2012/13 near North Bull Island in Dublin Bay, included a very special bird.  Photographed at least three times by Cian Merne, Richard Nairn and John Fox, it had a selection of colour rings on its legs.  It turned out that this bird had been marked by a Scottish ringer, Raymond Duncan, at the Montrose Basin, between Dundee and Aberdeen on the north-east coast of Scotland.  It had been caught as a juvenile, only a few months old, on 16^th September 2012, not long after it had left its breeding grounds in Iceland.  With its new colour combination of orange and blue rings, EX71920 flew south to Dublin Bay where it was first resighted in December by Christer Persson at the Santry River.   A day later it was seen in Lein Park Raheny before moving with the flock to feed near the Bull Wall until at least March.  By May 2013, it would be back in Iceland after a flight of at least 1,500 kilometres, which it could have undertaken in one day. We will be looking out for this bird again next winter in Dublin Bay. 

Black-tailed Godwit flock with colour-ringed 
bird at North Bull Island. Richard Nairn