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.