Wednesday, 21 September 2016

Clouded Vision: This month's top 40


We had a load of graphs in the last blog, which focused on the summer months, but as the year moves on, we should too. There are stacks of data to be written up and reported on this month, and because we’re sitting looking at graphs, trend lines and error bars all day every day, we thought we’d find a different way to represent what’s happening in the Bay this month.

Interpreted as “Word Clouds” are the top forty species that you can expect to see in Dublin Bay this month and next. While the position of the text is random, the size of the font represents the abundance of that species in September, based on our low tide data collected over the last three Septembers. 


The top 40 species recorded in Dublin Bay in low tide surveys in
 September 2013, 2014 and 2015. Font size is proportional to the
 number of each species recorded, but the positioning of the text
 is random.

There are lots of Black-headed Gulls, Oystercatchers, Redshanks and Herring Gulls around this month and good numbers of Black-tailed Godwits and Curlews too. The Brent influx hasn't really got going yet, but they are on their way.



Brent Goose will arrive in numbers over the coming weeks David Dillon 

We won’t get many Whimbrel at this time of the year, as the ones that dropped in to spend May with us on their way to breeding grounds, won’t bother calling in on their way to western Africa, and will just do the journey from Iceland in a oner.

Shoveler, Pintail, Wigeon and Teal are waiting in the wings, but won’t really make their presence known for a while yet. We’ll have to wait until mid to late October for decent numbers of any of these. It’ll be the last we see of the terns for a while too. The odd straggler into October wouldn’t be totally surprising, but the majority will have cleared out by now. 


And here’s a sneak peek of what October is likely to have in store. 

The top 40 species recorded in Dublin Bay in low tide surveys in
 October 2013, 2014 and 2015. Font size is proportional to the
 number of each species recorded, but the positioning of the text
 is random.



Friday, 2 September 2016

Summer holidays in Dublin Bay



We know quite a lot about the waterbirds that spend the winter in Dublin Bay, with decades’ worth of monitoring through I-WeBS (the Irish Wetland Bird Survey) and its predecessors having shaped our knowledge and formed a large database of information that can be drawn on. But year-round counts by the Dublin Bay Birds Project since 2013 have revealed a few surprises for summertime in the bay, showing that significant numbers of waterbirds are present outside of the core monitoring period for I-WeBS.

Black-tailed Godwits staging in Dublin Bay Liam Kane


I-WeBS counts have shown that Dublin Bay regularly hosts 33 waterbird species, and wintering numbers regularly exceed 30,000 waterbirds. Among those wintering are large numbers of ducks, geese, waders and gulls, with Light-bellied Brent Goose, Knot, Black-tailed Godwit and Bar-tailed Godwit occurring at internationally important levels. 

The general pattern is that bird numbers across the bay fall sharply after March, and are at their lowest levels in May and June. And then, from late June onwards, we start to see the numbers rising again, and several thousand birds are added each month, until the annual peak in January. 


Average number of waterbirds and seabirds recorded during monthly 
low tide counts between July 2013 and June 2015. Bars refer to the 
total number of birds recorded. Line refers to the average number 
of species recorded. I-WeBS core season = grey, I-WeBS off-season = green. 


In spring, the majority of our waterbirds head for their breeding grounds, and by the end of March many species have disappeared almost entirely. As the days draw out and the temperatures rise, we see the waterbirds in the bay becoming scarcer by the day. Spring soon gives way to summer: the lifeguards are posted on the beaches; the Little Egrets display their wavy plumes, and the skies are filled with melodious Meadow Pipits and Skylarks, raucous Common and Arctic Terns, and the buzzing chitchat of Swallows and Martins on their high-speed aerial chases. But our year-round surveys have shown that it’s not just terns and songbirds that provide the soundtrack for Dublin Bay’s summer. The mudflats are far from bare and silent - Bull Island, Sandymount Strand and the Tolka Estuary provide a rich species list for any waterbird lover.

Colour-ringed Bar-tailed Godwit "DH" in summer plumage Kim Fischer 


In summer, Brent Geese, Wigeon, Teal, Shoveler and Pintail are absent, as are Red-throated Divers, Red-breasted Mergansers and Great Crested Grebes. And like the waterfowl, Knot and Grey Plover are winter-only inhabitants of Dublin Bay, with the vast majority of them recorded between September and March. 

But this isn’t the case for all waders and the bay is particularly important for some species during the summer months. Whimbrel, a passage migrant in Ireland, is practically absent from the Dublin Bay I-WeBS dataset, as it only appears in the I-WeBS off-season. Highest numbers occur in May, when birds are moving northwards to breed, and in July, when they are en route to their wintering grounds. 

Black-tailed Godwits occur in the bay in internationally important numbers through the I-WeBS season, but April and August see significant numbers too. The spring influx starts in March and the birds are still present in April, before disappearing off to Iceland to breed. By July there are birds back in Dublin, and by August their numbers have risen to exceed the international threshold once again.  

Oystercatchers, too, are a Dublin Bay staple, being present in each month of the year. Numbers during the winter are much higher, but the threshold for national importance is exceeded in four out of the five I-WeBS off-season months, showing how important the site is for them during the summer.   

Average number of birds counted per month 
on monthly low tide counts between 
July 2013 and June 2015. The orange lines refer to 
the 1% threshold for national importance, and the grey 
line refers to the 1% threshold for international 
importance. Note that Whimbrel numbers in Ireland
 do not reach the international threshold and no 
thresholds of national importance are available. 

So, through this project, we have been able to appreciate the year-round importance of Dublin Bay for some waterbirds, and have been able to see just how important it is as a staging site in spring and autumn. Although the official I-WeBS period is September to March, the I-WeBS Office will very happily accept any counts taken in the off-season, as they may shed new light on the importance of other sites during this period.

Friday, 8 July 2016

Return On Investment

The Dublin Bay Birds Project team took the opportunity to colour-ring some adult common terns on Sandymount Strand, County Dublin last autumn and our efforts have already been rewarded!

We have blogged a number of times about ringing the tern chicks that are born at the Dublin Port breeding colonies. But did you know we have also managed to successfully catch and tag adult birds? Of course we don’t do this at the colonies or even within the nesting season as that could potentially disrupt adult birds incubating and feeding young for example.


Newly fledged Common Tern at Dublin Port
 with metal and colour ring (on left leg) on view
John Fox

Instead we carry out the tagging of adults at Sandymount Strand during the post breeding season (Late august – September). Terns of various species gather and roost here in the early autumn before migrating south for the winter. We know all the birds are not derived from the Dublin colonies from the numbers that accumulate and from the occasional presence of Sandwich Terns (who don’t breed in Dublin) and even Black Terns (which don’t breed in Ireland at all!) You can read all about this pre-migration mass roost at Sandymount Strand here.


A mixed tern flock arrives to roost at Sandymount Strand Dick Coombes

With the ringed chicks it can be three years or more before we would expect to see them on Irish shores once more as it will take this long at least for Common and Arctic Tern chicks to reach sexual maturity and return to the colonies to breed. Adults on the other hand if they survive the winter and migration will be back the following year and we could potentially spot them by re-sighting and reading the ring which in turn may tell us for example, what colony they are breeding and if they successfully rear young.

So we were pleased when our BirdWatch Ireland colleague Brian Burke got in touch from Rockabill Island in early June to ask us if we recognised a few colour ringed Common Terns he had managed to photograph! On inspection of the photos we could confirm our first resightings of the birds since been ringed in Autumn 2015. We also knew instantly that we had ringed them as adults as we place the colour ring on the right leg of adult birds (to avoid confusion as the same colour rings are used on both chicks and adults). 





3 colour-ringed adult Common Terns seen on Rockabill Island,
 PFX, PHL and PKN
Brian Burke


We ringed "PFX" on August 26th, "PHL" on September 7th and "PKN" the very next evening on the 8th, all in 2015. You can see how they are getting on at Rockabill this year here.

We now look forward to the rest of the breeding season to see if any more of our colour ringed birds will show up in Dublin or elsewhere in Europe. The excitement builds as we approach the cusp of the breeding season when we can once more admire the big roosting flocks at Sandymount Strand (and maybe even catch and colour ring a few!).


A short trip for a Common Tern,
Rockabill (north) to Sandymount Strand (south), 

a little over 20 miles apart Google Maps


If you think you have seen one of our colour-ringed terns or any colour ringed bird in Dublin for that matter be sure to let us know at dublinbaybirds@birdwatchireland.ie  

For more info on the colour ringing schemes in operation in Europe see here.


Monday, 16 May 2016

Running Rings Around Me


A Dublin Port Common Tern colour-ring has been recovered on Rockabill, but all is not as it seems.  

Part of our routine monitoring of our tern colonies involves ringing (and sometimes colour-ringing) the chicks before they fledge. And a good proportion of the chicks that hatch on the east coast of Ireland each year are ringed. Over time, this allows us to build a picture of where these birds go, but also whether they return to breed in the colony where they hatched, or in a different colony. By keeping track of this, we can work out what level of mixing happens, and which colonies are acting as population sources or population sinks. Terns don’t start to breed until they are three years old, so we have to play a waiting game between ringing the chicks and re-sighting the adult birds when they return to breed.   

Ringed adult Roseate Tern Dick Coombes

Earlier this week we received word from the tern wardens on Rockabill, saying that they had found a tern colour-ring out there. We knew from the colour of the ring and the inscription (PST) that it was a ring that has been assigned to the Common Terns breeding on the ESB Dolphin in Dublin Port. And while it was disappointing to find out that the blue ring with white inscription “PST” hadn’t managed to get any further than Rockabill, it caused us to wonder if Dublin Port-ringed birds often visited Rockabill between fledging and migrating southwards for the winter.

Rockabill Island (30 km fro Dublin Port) Brian Burke

Of course one recovery or a ring cannot answer all of our questions, but it seemed like a good start… However, a quick look at the database, resulted in alarm bells, and more questions - PST wasn’t there! Was the database working incorrectly? Or was it human error, and had we sent birds off to Africa without keeping a record of their details? We were starting to feel pretty PST off!! But thankfully, after checking the record of broken rings, we realised that this wasn’t the case. PST had snapped during ringing and had never made it to a bird’s leg at all – one of us picked up the broken ring and pocketed it. 

"PST" colour-ring found on Rockabill Island 
on May 8th, 2016 Brian Burke

The ring didn’t get to Rockabill, 30 km away, by wing as we initially thought -  it made the trip in a powerboat with the same ringers the following week! Presumably, it then fell out of on of our pockets, and was later picked up by one of Rockabill wardens.

So, the two take-home messages are:
  • We definitely, definitely didn’t doubt ourselves or our record keeping for a second
  • Those Rockabill wardens know every inch of that island and don’t miss a thing

The observation hide overlooking the Kilcoole
 Little Tern colony Paddy Manley

As the number of terns build up, this is a great time to get out to the Tolka Estuary in Dublin, Kilcoole Beach in Wicklow or Lady's Island in Wexford to see these beautifully delicate, but still totally badass, seabirds breeding along our coasts. Keep an eye out for our colour-ringed ones too!


Wednesday, 6 April 2016

All at Sea: Migrating Oystercatcher checks out research vessel


One of our trusty project contributors and prolific ring-reader, Niall T. Keogh, is on a boat hundreds of miles away, in the middle of the ocean, but he’s still managing to find reasons to get in touch with us about Oystercatchers, and we're so glad that he did!

“Monday 28th March 2016 saw the R.V. Celtic Explorer over the Rockall Bank, approximately 245 nautical miles WNW of Tory Island, Co. Donegal. The seabird and cetacean survey team from the Marine and Freshwater Research Centre GMIT and the Irish Whale and Dolphin Group were out on deck collecting observational data during the annual Blue Whiting Acoustic Survey. We had stopped to deploy a CTD (for measuring water temperature, salinity etc.) and while enjoying nice views of a Great Shearwater circling the ship the unmistakable call of an Oystercatcher could be heard! The bird (in full breeding plumage) was seen flying around the ship, calling loudly and looking rather worried as it was being actively chased by a Fulmar!”

Location of the Oystercatcher sighting from the
R.V. Celtic Explorer over the Rockall Bank

Iceland-bound Oystercatcher being chased
 by a Fulmar
Niall T. Keogh
This is a great record, and while this might sound strange at first, an Oystercatcher out in this part of the sea at this time of the year is to be expected really. It’s most likely on its way to Iceland for the breeding season.

We know that three of our Dublin-ringed Oystercatchers are already there, and it’s the second year that each have had their colour-rings read there. JA was reported in Sandgerði in the southwest on the on the 19th March, and the next day XT was re-sighted in Leirhöfn in the north east. And just a few days ago, on April 1st, CU was picked up in Stokkseyri in the southwest.
Oystercatcher CU replenishes its energy with a tasty
 snack after a long flight Tómas Grétar Gunnarsson
Niall also mentioned that another two Oystercatchers were seen flying north together over the middle of the Rockall Trough a few days later.


Visible migration. Sure it’d blow your mind…  

Friday, 18 March 2016

Next stop Iceland for these leggy beauties!


Dublin Bay hosts internationally important numbers (that is to say that more than 1% of the flyway population) of Black-tailed Godwits each year. From late summer, normally towards the end of July, Blackwits begin to arrive back to Ireland from Iceland. It is often the failed breeders that arrive first, with the breeders and the juveniles coming slightly later on. They tend to arrive quite suddenly to Dublin Bay. Our first July count last year amounted to 159 birds, but this had doubled by our next count, ten days later. We get an autumnal peak (7 or 800 birds) in Dublin Bay in September, but the flocks soon disperse. Then, as the winter progresses the numbers gradually grow before peaking at about 1,500 birds in March and early April. And by May, they’re gone.

Flock of Black-tailed Godwits in springtime Liam Kane

Right now Black-tailed Godwits are focused on feeding up and getting in condition for migration in the coming weeks. But they also need to get plenty of energy on board to fuel a complete change of their body feathers. Many have started this spring moult, which effectively is them putting on their glad rags for the breeding season. They will transform from a palette of grey into vivid burnt orange on the head, neck and chest with the flanks and belly strongly barred, the wings held closed have coarsely spotted orange, white and black feathers amongst mainly grey white fringed feathers.

Springtime in Dublin Bay presents the fantastic opportunity to observe these beautiful birds as they transform into their summer finery. An international team of Godwit researchers  are keen to investigate the regional differences in the timing of moult - some of the birds that winter in Portugal start their moult earlier than our birds up here. They are looking for your help to piece this story together. Read more about this on Wadertales - a fantastic wader-focused blog, which is definitely worth checking out.

A colour-ringed Black-tailed Godwit was recently spotted in the South Lagoon on Bull Island. This bird was originally ringed as a juvenile bird in the Montrose Basin in north east Scotland in 2012, and is now a regular to Dublin Bay. We have become very familiar with this bird over the past few years and have followed his movements around Bull Island and the surrounding parks and pitches. You may remember him being mentioned on our blog previously; find out some more about this guy here and here.

Colour ringed Black-tailed Godwit Richard Nairn


With the Black-tailed Godwit regional moult survey fast approaching, why not get out to your local patch and see how your Blackwits are looking? It would be really interesting to see where the Black-tailed Godwits wintering in Dublin Bay sit within the international moult trend. The coordinated observation period is the Easter weekend - the 25th and 28th of March. Read the full instructions and all the details on the Wadertales blog. 


Tuesday, 8 March 2016

Dublin Bay Oystercatcher: an Oransay regular

One of our Dublin Bay Oystercatchers is becoming a regular on Oransay in the Inner Hebrides. Morgan Vaughan, RSPB warden up there, tells us about how he crossed paths with Oystercatcher “UA”.


I am fortunate enough to carry out a WeBs survey for the BTO which falls within the South Colonsay and Oronsay SSSI, Argyll, Scotland. The two inner Hebridean islands are separated by a tidal strand and this is where I carry out the monthly survey as part of the monitoring work as warden of RSPB’s Oronsay. I tend to count on a rising tide shortly after low water as this pushes the waders out from the skerries of the islands peppered through the strand to feed along the water’s edge. This also gives a readily countable stretch of sand to work along. The intertidal zone is flanked by costal heath, maritime grassland and salt marsh, all of which granted protection for chough, corncrake and grey seals.

Colonsay and Oransay and the intertidal area
where Oystercatcher "UA" hangs out

During the March count (16/03/2015) last year, I spotted a colour-ringed oystercatcher close enough to get the colours and I could see that there was an inscription on one of the yellow rings, but it was just too far away to make out. I returned eagerly the next day with camera in hand and managed to find the bird again in the same spot and snapped a usable photo. UA.

Oystercatcher "UA" foraging on the sandflats
between Oransay and Colonsay
Morgan Vaughan

I’d worked out on the day that it could be potentially a Dublin Bay bird and with great excitement I fired the photo off to Niall Tierney who promptly informed me about the bird’s history; “The bird was caught on the 22nd November last year [2014] and has only been seen once since then, on the 27th November, back at the ringing site”. I’m always so pleased with a result like this. Finding out the history of a ringed bird, especially an international traveller is always marvellous!

I kept a close eye while surveying our breeding waders on Oronsay for any other oystercatchers with rings, but no sign of UA. I’m always on the look-out for rings, a minor obsession borne out of my work with colour ringed chough, but I had no further sightings on the strand.


Oransay landscape Morgan Vaughan
Nearly a year on (23/02/2016), I’m on the strand again, counting on the incoming tide, and there’s UA once again - close enough to make out with the eye!  It is fascinating to wonder where this bird has been for the last 11 months. Perhaps it has been breeding somewhere nearby. I will be certain to be on the watch for it again during this year’s breeding season.