Wednesday, 28 August 2019

A Tale of Two Oiks

Over the summer months we’ve been receiving reports of how our feathered friends are faring at far-flung breeding grounds. So, for this blog we’re going to open the files and take a look at how two of the Dublin Bay-ringed Oystercatchers, or ‘Tjaldar’ in Icelandic, got on over the last few months.

Oystercatcher on breeding territory, Scotland
Photo by Thomas McDonnell

Gudmundur Orn Benediktsson or Bói, is helping the University of Iceland with a colour-ringing project they have been running for several years. In the process, he has collected a fabulous amount of data on colour-ringed waders in Iceland, one of which - luckily for us - is the Oystercatcher ‘XT’.  

Oystercatcher 'XT' on breeding territory at Leirhofn, Iceland 2018
Photo by Gudmundur Orn Benediktsson 

XT was colour ringed by the Dublin Bay Birds Project (DBBP) in 2014 at Sandymount Strand in Dublin Bay. In April 2015, the first ever resighting of this bird was made by Bói in Leirhöfn, Iceland, 1,550 km from Sandymount Strand as the Oik flies. Since then, Bói sees XT in Iceland every summer, with us seeing XT back in Dublin Bay each winter. Already this bird has been spotted at Sandymount after an impressive return migration from Iceland (August 2019).

The journey to and from Leirhöfn, Iceland each year if XT takes the most direct route. A distance of 1,550 km each way.

XT is an early bird, being one of the first of the Oystercatchers to arrive on the breeding grounds in Leirhöfn each year since Bói has been following its progress. This year, Boi first observed it on March 10th which is the earliest observation he has had of it to date on that breeding territory. Leaving Ireland’s more temperate climate this early in the season is an ecological gamble.

On the one hand, as one of the first Oystercatchers to arrive XT faces less competition for suitable breeding habitat and can begin to breed earlier. This gives its offspring more time to gain weight and condition prior to migration back to wintering grounds, which increases their chances of survival on the arduous journey (Gill et al, 2013).

XT's nest at Leirhofn, Iceland 2018
Photo by Gudmundur Orn Benediktsson 

On the flip side, during the first two weeks of March in 2019, daytime temperatures in northern Iceland ranged from -5°C to 4°C during the day, and -15°C to 0°C at night (Accuweather historical data). Surviving these freezing temperatures, particularly following a trans-Atlantic migration when the need to feed is of critical importance for these birds, is energetically very costly. Despite these tough conditions, we were delighted to hear from Bói that XT and its unringed mate managed to produce young this year, showing the resilience of these feathered fowl!

Oystercatcher with leggy chick!
Photo by John Haslam

Closer to home, John Bowler the RSPB Scotland Island Officer for Tiree, has been keeping us up to date on how ‘ZN’, another Dublin Bay colour-ringed Oystercatcher, has been faring. 

Oystercatcher 'ZN' on breeding territory at Loch a’ Phuill, Isle of Tiree, Scotland
Photo by John Bowler

ZN found love with the Welsh-ringed bird ‘AY5’ in April this year. AY5 was ringed at Bangor Harbour in Gwynedd, Wales, in January 2014 by Stephen Dodd of the RSPB (who, incidentally, has submitted observations of some of our other colour-ringed terns to us!). These two birds flew a combined 760 kilometres one way in order to raise the next generation! 

Oystercatcher and Sanderling flock
Photo by Kevin Murphy

Ring-reading gives us a fantastic insight into migration. It tells us when birds are beginning to migrate, changes in timing of migration, areas which are important to these species both as final destinations and pit stops, longevity and survival rates. So, a massive thank you to Gudmundur and John and Stephen, and everyone else who has read colour-rings, and sent them in to us! Ye’re a fabulous bunch! 

Ring reading waders on Sandymount Strand in Dublin Bay

If you spot an Oystercatcher, Bar–tailed Godwit or Redshank colour-ringed by the Dublin Bay Birds Project you can submit your resighting here. They really are appreciated! The DBBP colour-ring combinations are shown below. Birds colour-ringed at North Bull Island have a blue colour-ring with no inscription on the left leg rather than a yellow one.

Dublin Bay Birds Project colour ring combination for wading birds ringed on south Dublin Bay
Photo by Richard Nairn

Dublin Bay Birds Project colour ring combination for wading birds ringed on north Dublin Bay
Photo by John Fox

From all in the Dublin Bay Birds Project team, thanks so much!!

Gill, J.A., Alves, J.A., Sutherland, W.J., Appleton, G.F, Potts, P.M., and Gunnarsson, T.G. 2013. Why is timing of bird migration advancing when individuals are not. Proceedings of the Royal Society for Birds.

Thursday, 20 June 2019

Mid-season update from the Dublin Port Tern colony

The Tern season is in full swing, and Dublin Port, with four structures set aside for nesting Terns, is alive with the sounds and sights of Common and Arctic Terns busily raising the next generation.

Terns over ESB platform in Dublin Port
Photo by Tara Adcock

So far this season we have carried out two nest censuses of the Arctic and Common Tern colony breeding in Dublin Port. Numbers have increased significantly over the last 35 years, going from 38 pairs in 1984 to nearly 600 nests last season.

In total, four sub-colonies of Arctic and Common Terns nest in the port on man–made structures, (see this and this blog post for a background to the Dublin Port Tern colony and DBBP’s work). These have been re-purposed specially for breeding Terns, with gravel added as a nesting substrate, and chick shelters placed on each. Our job is to make our way to the breeding structures under the able navigation of Jimmy Murray and colleagues from Poolbeg Yacht Club, and count the number of nests, eggs per nest, and chicks. As of the last census, we have counted nearly 600 nests this season, which, all going well, means it looks like we are on track for another successful breeding season on most breeding platforms in the port.

Jimmy Murray, our able captain. The black pipes on the platform act as chick shelters.
Photos by Tara Adcock.

Nest censusing.
Photo by Tara Adcock.

Counting Tern nests sounds like a straight-forward task, and it is, once you get the eye in. However, when confronted with your first nest census, it can feel a bit like a game of Where’s Waldo. Terns don’t construct nests in the sense that we are traditionally familiar with. Instead, they make a small hollow or scrape in the ground and lay the eggs in this. To make it a little more difficult for potential predators, the eggs and chicks are well camouflaged, using dark blotches against a lighter background. This technique is known as disruptive colouration and works by breaking up the outline of an object (Stoddard et al. 2016).

Two Tern chicks and one egg.
Photo by Helen Boland.

Two Tern chicks
(one newly hatched and still wet).
Photo by Helen Boland.

To add an element of danger to the whole process, Common and Arctic Terns are fiercely protective of their offspring, often dive-bombing us as we move about the platforms. Terns subscribe to the philosophy of ‘strength in numbers’. They typically prefer to nest in large colonies, where they practice what’s called ‘group mobbing behaviour’, working as a team to drive intruders away from the breeding site (Mallory 2016). Thanks to their ability to work together, increasing numbers within each sub colony will go some way to protect these Terns from potential predators. (See below for a video of the Dublin Bay Bird's Project, Ricky Whelan, being mobbed by a very persistent Tern!).

Once the nest census is complete, it is off to the hide - supplied by Dublin Port Company earlier this year on one of the platforms - for some Tern ring -reading. The hide is a wooden structure, with three windows that allows us to view the Terns, while limiting disturbance to them as a result of our presence. We’ve also found that it’s relatively roomy, and can squeeze in three adults, a scope, and a stool, albeit with some contortions necessary at times! 

Three in the hide and the little one said...
Photo by Helen Boland.

The purpose of placing a hide on one of the port structures is to find out whether Terns which hatched in the port are returning to the port to breed, and if they are, whether they are nesting on the same structures from which they fledged. (For a view from the hide, click the video below).

On the first trial, we got our first colour-ringed Common Tern, ‘PAL’. PAL was ringed by the Dublin Bay Birds Project in 2015 as a pullus (unfledged chick), on the nesting structure in the Tolka Estuary, making this bird four years old. Common Terns become sexually mature from three to five years of age and seeing this bird landing within the nesting area of the CDL Dolphin, at least suggests that it has returned to the port to breed, potentially for the first time!

Common Tern ringed at Sandymount Strand in 2018.
Photo by Helen Boland.

Our second visit to the hide yielded yet another ring-resighting, this time of a Common Tern ringed by BirdWatch Ireland in the Port in 2011 on the SPA-designated nesting platform owned by ESB. This bird, at eight years old, is of definite breeding age!

Monitoring and working to protect a species and habitat always comes with its own unique set of challenges, and the Tern colony in Dublin Port is no exception. This year, one nesting platform in Dublin Port has unfortunately suffered heavy predation, but by what we aren’t yet certain. A motion-activated camera has been placed on the breeding structure to try to ascertain what exactly is going on, and once armed with this information we will hopefully have a clearer idea of how to protect the birds nesting within this sub-colony.

Terns in Dublin Port.
Photo by Helen Boland.

Last season, two structures were affected by rat predation. This year we have been monitoring for the presence of rats on all four structures, using non–toxic chocolate and coconut flavoured wax blocks. Rats have a sweet tooth, and the idea is that if they are indeed present that they would chew the flavoured wax blocks leaving us with evidence of their presence in the form of rat tooth marks. This is a very simple method which has proven effective and inexpensive. Some rat activity was recorded at the beginning of the season on two of the four structures, but thankfully thus far there has been no direct evidence of rat predation within the colony. These pressures highlight the need to continue to monitor and protect the Tern population breeding at this site. 

Putting the wax blocks in place.
Photo by Helen Boland.

Monitoring block which has been chewed by rats.
Photo by Helen Boland.

Although this season has had a few bumps in the road, we are hopeful of a successful season for at least three of the four structures, and we are thrilled to have seen the first Tern rings on the structures. Identifying the predators which are affecting the sub–colony on the fourth structure will help us to further understand the pressures which can impact the breeding success of this colony.

Terns overhead during nest censusing.
Photo by Helen Boland.

Mallory, M.L. 2016. Reactions of ground nesting marine birds to human disturbance in the Canadian Arctic. Arctic Science, 2: 67–77.

Stoddard, M.C., Kupán, K., Eyster, H.N., Rojas-Abreu, W., Cruz-Lopez, M., Serrano-Meneses, M.A., Kupper, C. 2016. Camouflage and clutch survival in plovers and terns. Scientific Reports, 6: 32059.

Tuesday, 30 April 2019

Terning our attention to summer

Winter is finally ending and with its passing so too comes the departure of most wading birds from our shores as they move to breeding grounds further northwest and northeast. However, as numbers of wading birds drop we barely have time to catch our breath before the Tern season is upon us. Even now, numbers are beginning to build as these tiny seabirds return to our shores eager to get on with the business of raising the next generation. So to celebrate both the turning of the seasons and the arrival of these beautiful sea swallows (as Arctic and Common Terns are affectionately known), we thought we would provide a brief overview of our work on the Tern colonies in Dublin Port.

Terns flying overhead as we land on one of the structures in Dublin Port Helen Boland

When picturing seabird colonies, an urban port is probably one of the last places we would expect to find a bustling seabird colony. Yet for Common and Arctic Terns, Dublin Port has long been an important breeding site, with records dating back to at least 1949 (Merne 2004). 

An All–Ireland Tern survey in 1984 found that 61 Common Tern and 30 Arctic Tern pairs were nesting at this site (Whilde 1985). Since then, numbers breeding in the port have increased significantly. Nearly 600 Common and Arctic Tern nests were recorded in Dublin Port in 2018 during censusing work carried out by BirdWatch Ireland’s Dublin Bay Birds Project. 

Tern chicks on the Great South Wall pontoon Helen Boland

So what makes the port ideal for these breeding Common and Arctic Terns? One factor is food, and Dublin Port is perfectly situated for this purpose, with plenty of small fish such as sprat and sandeels, the Terns preferred prey. A second consideration is safety of their young from predation. Seabirds have generally evolved to nest on islands and cliffs as these habitats provide a degree of safety from mammalian predators.

Common Tern offering a sand eel to its mate Neil Harmey

In Dublin Port, infrastructure such as pontoons and dolphins (large wooden structures with a concrete or metal platform rather than the loveable cetaceans) act as mini islands, ideal for nesting terns. Four structures (two dolphins and two pontoons) support colonies of Common and Arctic Terns in the port. The two pontoons were deployed by Dublin Port Company in 2013 and 2015, specifically for this purpose. One of the dolphins, owned by the Electricity Supply Board (ESB), is now part of the South Dublin Bay and River Tolka Special Protection Area due to its significance as a Tern breeding site. The continued commitment of the Dublin Port Company and ESB to providing a safe space for these breeding birds is one of the reasons why these colonies are thriving.

ESB Dolphin (SPA) Helen Boland

Not only do we carry out Tern nest censusing work in Dublin Port, but we also undertake significant ringing efforts of chicks at the site. Last year alone, over 650 Arctic and Common Tern chicks were fitted with a BTO metal ring each of which has a unique inscription used to individually identify birds. In addition, 125 Common Tern and 10 Arctic Tern chicks were fitted with colour rings (and hundreds more since 2015), each of which also has a unique code. The inscriptions on colour rings, unlike metal rings, are large enough for volunteers and surveyors to read in the field using telescopes (albeit with quite a lot of patience!).

Ringing Tern chicks Helen Boland

The aim of this work is to try to discover whether terns return to breed on the same structure on which they hatched, or if they return to the colony at all. To aid us with this important work, Dublin Port Company have installed a hide (a small hut used to unobtrusively spy on birds), on one of the structures this year. This hide is based on the design used on Rockabill Island (north Dublin) which is home each summer to ~80% of northwest Europe’s breeding Roseate Tern population, and where BirdWatch Ireland manage a conservation project each summer. The installation of this hide marks an exciting new chapter in the Dublin Bay Birds Project. The timing could not be more perfect as the colour-ringing began in 2015, and chicks ringed in that year could now have potentially reached breeding maturity and could be prospecting for nest sites on the Dublin Port structures. All we need now is a member of staff, a telescope, a bit of patience and a sprinkling of luck and hopefully we can begin to learn about the fidelity of terns in Dublin Port to their natal structures.

The new hide provided by Dublin Port Company on the CDL Dolphin Tara Adcock

Colour-ringing also tells us a great deal about the areas both nationally and internationally which these birds are using, and their migration routes. Terns are ringed by the DBBP not only at Dublin Port, but also at Sandymount Strand in early autumn. At the end of each breeding season, literally thousands of Terns which have bred in Ireland and further afield gather at Sandymount Strand in post breeding aggregations. See here for a blog on these phenomenal aggregations. Terns are caught at this site using mist nets (large nets stretched between two poles) and colour-ringed before being released. So far, our colour-ringing efforts have yielded 73 resightings of 30 birds ranging from Ireland, Scotland, England, Wales, the Netherlands, Norway, Gambia and Namibia!

Juvenile Common Tern chick with colour ring John Fox

Finally, the ability for nature to survive, not only on the edge of a bustling capital city but cheek to jowl with industry, is in no small part thanks to a great team effort from a combination of organisations. Critical to this, of course, is the support, both financial and otherwise, provided to DBBP by Dublin Port Company. In addition, access is facilitated by ESB, and licenses are provided by NPWS, but with great interest and advice provided by all. It goes a long way to show the significant and positive impacts big organisations can have on wildlife when they work together to provide space for nature.

Terns flush overhead as the boat approaches the colony Helen Boland

Merne, O.J. 2004. Common Sterna hirundo and Arctic Terns S. paradisaea breeding in Dublin Port, County Dublin, 1995-2003. Irish Birds. 7: 369-374.

Whilde A. 1985. The 1984 All Ireland Tern Survey. Irish Birds. 3: 1-32.

Tuesday, 26 February 2019

All your gulls coming home to roost

DBBP’s very own resident rock star, Ricky Whelan, has been bringing his sell out speaking tour, 'The Secret Life of Crows', to packed audiences across the nation. The intelligence of these birds has captivated crowds and, much like a revival, has led to conversions to the ‘cult of the crow’, or in less dramatic terms, people left with a renewed appreciation for the cleverness of corvids.

An avian family which has been compared to corvids, both in terms of their cerebral qualities and their sometimes-controversial behaviour, is the gull family. While perhaps not as innovative as the New Caledonian Crow which uses sticks to transport multiple items (Jacobs et al 2016), gulls have shown a remarkable ability to ‘think outside the box’.

Herring Gull with chick
Photo credit: Brian Burke

If you have ever noticed Herring or Common Gulls, ‘dancing’ in your local park, what you are witnessing is them simulating rain drops by drumming their feet on the ground to encourage earthworms to the surface (Tinbergen 1953). For a video of a Herring Gull performing a ‘rain dance’ click hereTool-use has also been recorded, with a report of a Herring Gull using bread as bait to lure goldfish (Henry & Aznar 2006). Take a walk along the coast and chances are you will see gulls repeatedly dropping shellfish from a height until the shell breaks open (Ingolfsson & Estrella 1978). This ability to learn, innovate and adapt behaviour accordingly is what defines intelligence (van Schaik & Burkart 2011).

Common Gull
Photo credit: Brian Burke

Last week, as darkness was falling, the DBBP Team got in to position all around Dublin Bay - from Dun Laoghaire to Sutton - and counted over 29,000 gulls coming in to roost. But more on numbers shortly.

In all, Dublin Bay regularly supports five species of gull. These are, in descending order of relative abundance, the Black – headed Gull; Herring Gull; Common Gull; Lesser Black – backed Gull and the Great Black – backed Gull. Small numbers of Mediterranean Gulls have also been consistently recorded during the autumn and winter months on Dublin’s south side for the last number of years, a relatively new arrival to our shores. 

Mediterranean Gull
Photo credit: Brian Burke

We count gulls in Dublin Bay in our monthly surveys during which all waterbird species, as well as their behaviour and location, are recorded. Gulls, however, are tricky. They are often feeding inland or out at sea during the day so can be missed during the regular surveys. To get a more accurate picture we schedule additional, dedicated counts at dusk to get an estimate of the numbers using the bay to roost at night. What we have found is pretty fascinating.

Mixed gull flock
Photo credit: Brian Burke

At high tide at dusk - the conditions we usually select for these counts - the highest number of gulls are recorded on the south side of Dublin Bay, when overall numbers there can go northwards of 20,000. However, at low tide, it appears that the north side of the bay, specifically the Tolka Estuary, is the place to be for those of the gull persuasion. More than 26,000 gulls were recorded there at low tide in February 2012 (Cummins & Crowe 2012), and more than 12,000 were recorded over the same tidal stage in February 2014 (Tierney et al 2014). 

Great Black-backed Gull
Photo credit: Brian Burke

Black–headed gulls certainly rule the roost in terms of sheer numbers, often with 16,000+ recorded across the whole bay, and most of these usually at Sandymount and Booterstown. The second most numerous species during roost surveys is the Herring Gull, with more than 7,000 birds counted during a dusk survey. The difference in numbers of gulls recorded during core counts of all waterbirds present compared with dedicated dusk counts is particularly striking for the Black-headed Gull. The peak count for this species during a standard low tide core count in 2018 was over 5,000 in February compared to the 17,000+ recorded in the same month but during a dusk gull roost count.

Black-headed Gull in breeding plumage
Photo credit: Brian Burke

But why, aside from scientific curiosity, is this information important? Given the number of sandwiches and chips pilfered from unsuspecting humans, surely the population of Herring Gulls, if not all gulls, is very healthy? Published data, however, states that Herring Gull and Black–headed Gull are both red-listed as species of conservation concern in Ireland (Colhoun & Cummins 2013). This is due to a 90% and 70% decline respectively in the breeding populations of these birds between 1968 and 2002.

Common Gull, Lesser Black-backed Gull and Great Black-backed Gull are all amber listed as species of conservation concern. More recent monitoring of breeding populations in Ireland will hopefully show something more positive. And by gathering data on long-term trends and distribution in Dublin Bay, we can highlight any changes at what appears to be an important winter roosting site for these beautiful and intelligent birds, and hopefully the information can help inform policy to protect them.

Black-headed Gull in non-breeding plumage
Photo credit: Brian Burke

Finally, a note on our relationship with gulls. One aspect which we tend to forget is that gulls have lived in coastal areas and inland with us for centuries. Their presence now appears to be greater in coastal towns and cities for a number of reasons. One is our continued overfishing of the seas. As a result of overfishing, these intelligent birds were forced to find alternative methods of foraging and landed on, (both figuratively and literally), landfills. This led to wide outbreaks of avian botulism, a disease which causes paralysis, and in turn resulted in the Herring Gull population crash which led to the 90% decline cited above. When landfills closed, these birds were once more forced to find alternative food supplies, and as proficient scavengers, have been able to take advantage of the waste found on our streets and overflowing bins. Further to this, by feeding them scraps from our sandwiches and what have you, we have trained some of these birds to see us as a source of food, which has led to lunches being pinched by a few rogue gulls.

This change in the food web, from sea, to landfill, to scavenging from bins and streets, has also resulted in some species, the Herring and Lesser Black–backed Gull, to begin to nest on rooftops during the summer months, where they can more easily scavenge for their young broods. It is during this period that most of the human – Gull conflict arises. Gulls are fantastic parents who are, much like most human parents, wonderfully protective. This means that, particularly during the fledging stage during late June/early July - when Gull offspring are at their most vulnerable - these parents will protect their young by emitting high pitched warning calls or even putting their own safety on the line by swooping at people or pets who come too close to their young. This stage lasts for a couple of weeks after which Gulls go back to largely ignoring us.

During the summer months we need to remember that it is our actions which have driven them to nest amongst us. It is a visible, (and often audible), warning that our fishery policies and practices are causing knock-on effects across the ecosystem and that major reforms are needed to correct this. For an excellent piece on fisheries policies in Ireland see this recording by BirdWatch Ireland’s Fintan Kelly.

Lesser Black-backed Gulls
Photo credit: Brian Burke

Colhoun, K. & Cummins, S. (2013) Birds of Conservation Concern in Ireland 2014–2019. Irish Birds 9: 523-544.

Cummins, S. & Crowe, O. (2012). Collection of baseline waterbird data for Irish coastal Special Protection Areas 2011/ 2012, s.l. Report commissioned by the National parks and Wildlife Service and prepared by BirdWatch Ireland.

Henry, P.Y. & Aznar, J.C. (2018). Tool-use in Charadrii: active bait – fishing by a Herring Gull, Waterbirds, 29(2), pp. 233-234.

Ingolfsson, A. & Estrella, B.T. (1978). The development of shell – cracking behaviour in Herring Gulls, Auk, 95, pp. 577-579.

Jacobs, I.F., von Bayern, A., & Osvath, M. (2016). A novel tool-use mode in animals: New Caledonian crows insert tools to transport objects, [online], Animal Cognition, 19(6), pp. 1249-1252.

Tierney, N., Whelan, R., Boland, H., Valentín, A., & Crowe, O. 2014. Dublin Bay Birds Project Technical Report. BirdWatch Ireland report to Dublin Port Company.

Tinbergen, N. (1953). The herring gull’s world: a study of the social behaviour of birds. London, England: Collins.

van Schaik, C.P. & Burkart, J.M. (2011). Social learning and evolution: the cultural intelligence hypothesis, Philosophical Transactions of the Royal Society, 366.

Thursday, 31 January 2019

World Wetlands Day, February 2nd 2019, in Dublin Bay

World Wetlands Day is an international day of celebration, to commemorate the signing of the Ramsar Convention on Wetlands in the Iranian city of Ramsar in 1971. This massively important inter-governmental treaty provided the framework for the wise-use and conservation of wetlands around the world. It also formulated the criteria which are now used for identifying and placing legal protection on wetlands of significant importance. Dedicating a whole day to celebrating wetlands highlights their immense value and the need to protect them.  

With that in mind, we have compiled a short summary of what makes Dublin Bay such an important wetland site and why we dedicate so much of our time to studying it! We have also given some suggestions of when, where and how you can access Dublin Bay and observe some of its magnificent avian spectacles.
World Wetlands Day 2019 Logo 
Dublin Bay is designated under EU legislation as a Special Protection Area (SPA) due to the numbers of wintering waterbirds it supports. It holds internationally important numbers of Light-bellied Brent Goose, Knot, Black-tailed Godwit and Bar-tailed Godwit, and nationally important numbers of several other species. During our DBBP surveys the Bay regularly supports in excess of 30,000 waterbirds of more than 40 species, and, according to the Irish Wetland Bird Survey, it ranks in the top five most important wintering waterbird sites in Ireland! Dublin Bay is also a key site for breeding Common and Arctic Terns which breed on several structures in the Dublin Port area in summer months. Furthermore, massive flocks of terns (20,000+ at times!) have been recorded roosting on the intertidal mudflats along the south Dublin Bay coastline each autumn before making onward journeys to the west African coast to overwinter in its more favourable climate. 

Large feeding flock of Light-bellied Brent Geese - IBGRG

Dublin Bay is a truly special wetland site and with its proximity to the capital city it is easily accessed by residents and visitors. Everyone should make an effort to visit the bay and see some of the wonderful natural spectacles on offer. 

A flock of Golden Plover on the strand near Booterstown. Helen Boland. 

Some of the World Wetlands Day events in Ireland are listed here with the 'Birdwatching on Bull Island' talk and walk, organised by the Bull Island Volunteers, of particular relevance for Dublin-based people.

Seasonal avian highlights in Dublin Bay that you might consider checking out:

  • Brent Geese freshly arrived from arctic northern Canada can be observed feeding on the coastal mudflats close to Clontarf from October onwards. This small goose species has become so habituated to humans in Dublin it offers a unique opportunity to get close to these urbanised Arctic migrants.
  • Vast numbers of wintering waterbirds of geese, ducks, waders and gulls are found within the bay from October to March. At low tide the mudflats and marshes around Bull Island are alive with feeding flocks. You can observe flocks of Golden Plover and Knot, thousands strong, filling the skies above the wooden bridge as they whirl and roll in close formation. 
  • Breeding Terns are easily observed from the Great South Wall (GSW) on balmy June and July days as they commute to and from their nest sites along the River Liffey. Watch adult terns fish in the surf south of the GSW and return with beak-fulls of tiny fish prey to hungry chicks waiting impatiently further up river. 
  • From mid-August and into late September Sandymount Strand hosts a massive mixed flock of Common, Arctic and Roseate Terns. The birds coalesce into spectacular flocks as the evening light fades and before they roost overnight on the sandflats close to Merrion Gates. This is a natural spectacle that has become an annual pilgrimage for many wildlife enthusiasts. 

A large group of birdwatchers gathers
to observe tern flocks on Sandymount Strand. Jen Lynch. 

Accessing Dublin Bay by public transport: 

  • Dublin Bus 130 will take you from Lower Abbey Street all the way to Bull Island Wooden Bridge.
  • The DART serves Clontarf Road Dart Station which is within easy walk of the Tolka Estuary, and a little longer walk on to Bull Island. 
  • The DART also serves Booterstown Dart Station which brings you into the thick of things on Sandymount Strand. You can even view the autumn tern gatherings from the pedestrian overpass at the station. 
  • A number of Dublin Bus routes (1,18 and 47) serve Seafort Ave, Marine Drive which will take you close to Irishtown Nature Reserve. Follow the coastal path that will bring you east onto Pigeon House Road, continue along the waters edge to the Great South Wall. 

Tuesday, 18 December 2018

And a... godwit... in a pear tree?

When you think of Christmas the first bird that comes to mind is probably not the Bar-tailed Godwit. Yet there is one similarity between this bird and the jolly bearded man who delivers Christmas from the Arctic Circle - the journeys each undertakes.

The Bar-tailed Godwit subspecies, Limosa lapponica baueri, holds the record for the single longest non-stop migration of any avian species, clocking up between 10,000 and 11,000 km as it crosses the Pacific Ocean from its breeding grounds in Alaska to its wintering grounds on the shores of Australia and New Zealand. Closer to home, ‘our’ Bar -tailed Godwit subspecies, Limosa lapponica, admittedly has a slightly easier time of it, migrating from the Arctic Circle in Norway to overwinter on Irish shores from late August until March or April. That being said, I don’t think I’d fancy swapping my daily commute for their biannual trek.

Bar-tailed Godwit in winter plumage with satellite tracking device attached to its back.
John Fox.
Prior to undertaking such long migrations, these little birds must first ‘bulk up’. Their fat reserves increase phenomenally, finally comprising over half their body weight while their digestive organs shrink to accommodate this increase. As  Bill Bailey so aptly put it, this is a ‘form of self- cannibalisation’ (1), a gory feat which Santa Claus has thus far been able to forego.

The Dublin Bay Birds Project colour-ringing scheme, which began in 2013, has shed some light on the migration patterns of Limosa lapponica. With the aid of volunteers, one Bar-tailed Godwit, (DH), ringed on Sandymount Strand, has been recorded in Norway in the months of May and July over four consecutive years. This suggests that 'DH' is breeding in Norway, a finding supported by ‘An Atlas of Wader Populations in Africa and Western Eurasia’(2).

Bar-tailed Godwit ‘DH’ in breeding plumage – photo taken in Denmark.
Kim Fischer.
Colour-ring resightings have also revealed the potentially significant sites for these birds during their migration, with reports of Bar-tailed Godwits ringed by the Dublin Bay team submitted by volunteers in Denmark, the Netherlands and, most recently, England, prior to or following the breeding season.

Resighting locations of Bar-tailed Godwits outside Ireland.

Colour-ringing has also revealed some interesting patterns in terms of how Bar-tailed Godwits use Dublin Bay. Although all the Bar-tailed Godwits colour-ringed by the scheme so far were ringed on Dublin’s southside at Sandymount Strand, these marked individuals have been recorded using both the north and south sides of the bay. This is in contrast to the Oystercatcher which appears to be a bit more site-faithful. Many Oystercatchers ringed by the Dublin Bay Birds Project at either Sandymount Strand or Bull Island on Dublin’s northside, have only ever been resighted in Ireland at or near to these sites. For instance, two - hundred and fifty Oystercatchers ringed at Sandymount Strand have been resighted in Dublin Bay since 2013, with only 42 of these birds observed in the northern portion of the bay. Therefore, while Oystercatchers appear to largely conform to Dublin’s northsider/ southsider divide, Bar-tailed Godwits seem a more flexible bunch, availing of foraging and roosting opportunities on both sides of the bay.

Resighting locations of Bar-tailed Godwits in Dublin Bay. All Bar-tailed Godwits were ringed at Sandymount Strand on Dublin's southside.

Understanding the sites which are important to these incredible little birds on their migration to and from the Arctic and on our own shores outside the breeding period, enables greater national and international cooperation in protecting these sites. Colour-ring resightings feed into these conservation efforts and are a vital way to make a difference. Also, I have it on good authority that Bar-tailed Godwits act as spies for Santa Claus (courtesy of a five-year-old from Australia), so getting out and ring-reading may not only aid waterbird conservation but also pay off next Christmas!

Finally, from everyone in the Dublin Bay Birds Project, we wish you a Merry Christmas and Happy New Year. A massive thank you to everyone who has submitted ring resightings over the last number of years, your help really is invaluable!

(1) Bernhardt, A. (2016). ‘Interview: Bill Bailey on birdwatching, bar-tailed godwits and Brexit’ Country and Town House.
(2) Delaney, S., Scott, D., Dodman, T., & Stroud, D. 2009, An atlas of wader populations in Africa and Western Eurasia, 1st edn, Wetlands International, The Netherlands.

Friday, 9 November 2018

The Dublin Bay Birds Project - a quickfire digest of recent events (dive-bombing terns to evening gull watches)

We are continuing our quest to fill many of the gaps in knowledge about how birds use Dublin Bay. Being immersed in fieldwork and data the last while means we have not been blogging as often as we like to. It is now time to take stock, and look at what has been going on.  
The 2018 summer was equal parts challenging and exciting with a big focus on the breeding tern colonies in Dublin Port, while also doing the monthly low and rising tide counts of the whole bay.

But first let's take a moment to mention the DBBP video we made with Dublin Port Company and our friends in Media Coop. We had a lot of fun making it and the bird footage is STUNNING. In case you haven't already seen it, there is a little taster below as the full video can't upload here.  Full video available at this LINK.

Back to the terns. Oh the terns. No matter how many times we make the trips out to the Dublin Port tern colonies by boat, it never, ever gets old. The contrast of nature at its most dynamic and vital – 1000+ terns industriously incubating eggs and protecting nests and screeching in the air around the colonies - juxtaposed with the similarly industrious shipping vessels and port traffic going about their business all around them is an extraordinary sight. And we feel privileged to have the opportunity to be among the birds like this, up close and personal (sometimes very personal with direct hits to our heads from defensive adult terns). Plus, seeing the city from a boat in the Liffey Channel on a sunny day is pretty special.
Tara from the DBBP Team assisting with Common Tern data collection on the Great South Wall pontoon in July 2018. Helen Boland

In 2018, there were at least 596 pairs of terns, mainly Common but a few Arctic too, that nested on the four structures in the port area. The SPA-designated structure underwent significant upgrade works, carried out by ESB, and the terns seem to have adjusted to their excellent, new, specially designed platform. And the pontoon that was re-located pre-summer to a location close to the Great South Wall provided great views for walkers along the wall with a high volume of tern activity easily visible. You can read more about the summer tern monitoring in previous blog posts here and here

Post-breeding tern flocks at Sandymount
Once August arrived we began looking out for the huge annual congregations of post-breeding terns along Sandymount Strand. This is quite the event with thousands of terns gathering in the bay each night just before their southerly migration. As we’ve said here before, Dublin Bay has shown itself to be massively important over those few short weeks in August and September. The highest count we had this year was 6,700 ‘Commic’ Terns - Common and Arctic combined - in September (not quite the heady heights of 17,440 from September 2016 but impressive all the same!). And we had the pleasure of being joined by the South Dublin Branch of BirdWatch Ireland that evening to soak up the sheer spectacle of it. More about these awesome (in the proper sense of the word) tern gatherings here

The DBBP Team with the South Dublin Branch of BirdWatch Ireland looking at thousands of Terns in September on Sandymount Strand. Helen Boland.

In addition to the 135 tern chicks we colour-ringed at their nest sites we also managed to fit colour-rings to three fully-grown Common Terns that we caught in mist-nets in the dark after one of the flock counts in September. Hopefully these birds will be seen somewhere along their flyway helping us understand more about where they go. One of the Common Terns, ‘PFF’, that we colour-ringed in Autumn 2015 at Sandymount, has been seen three times since then in winter in the Gambia! Some previous observations of our colour-ringed terns are described here.

A Common Tern fitted with a Dublin Bay Birds Project, uniquely inscribed, colour-ring ‘2P3’ in September 2018. Helen Boland.

But now we're back in winter mode and the next task for the DBBP Team is a dusk gull roost count next week. It is incredible how many more gulls are present in the bay in the evening having been inland or at sea all day. We wouldn’t have a clue how important the bay is for gulls if we didn’t carry out specially tailored counts like this. Last year we counted more than 34,000 gulls one evening in December, mostly Black-headed Gulls (~29,000), with Herring, Common, Great Black-backed and Lesser Black-backed taking up the rear in that order.  Let’s see what we find next week. Then we move on to our third high-tide roost survey of 2018, with a dawn Brent census coming down the line too. And all the while we have been dealing with the steady influx of wader colour-ring resightings of our Dublin Bay Oystercatchers on their breeding grounds in Scotland and Iceland. More on all of that soon in another post.

We will share our news and findings more frequently now that we are back on top of our hectic schedule again! The information we are gathering improves our understanding of birds, how they use the bay, and what areas are particularly important for them, and hopefully it can help with informed decision-making about Dublin Bay.