The oystercatchers of Tiree

John Bowler, RSPB Scotland’s Tiree Officer, shares the story of Tiree’s visiting oystercatchers from Ireland and Wales.

The oystercatchers of Tiree   

The first colour-ringed Oystercatcher to be found on the Scottish Inner Hebridean Island of Tiree was bird VT, which was found nesting at Gott Bay in May 2015 and again in May 2016. VT had been ringed in Dublin Bay, Ireland in December 2014. As a result of this discovery, more detailed checks were made on the large number of Oystercatchers that breed on Tiree’s beaches and machairs. By the end of 2019, a total of 10 different colour-ringed Oystercatchers had been recorded on the island, of which eight had been ringed in the Dublin Bay area of Ireland and two had been ringed in Wales.

These findings fitted in with the pattern of earlier metal-ring discoveries from Tiree, with birds found dead in the spring and summer on the island having been ringed in the winter on the Gower in South Wales, on Anglesey and on Jersey. It is clear that many of the Oystercatchers that breed on Tiree are summer visitors to the island, who then go on to spend their winters further south, mostly along Irish Sea coasts. We also have large numbers of wintering Oystercatchers on Tiree. It is thought that many of these come from sites further north, including Iceland, as is known to be the case on the Outer Hebrides, although ringing data from Tiree are currently lacking to support this idea.

Oystercatcher XN

One of the Dublin Bay birds, XN, has bred annually on the RSPB Reef reserve on Tiree since 2017, returning each spring to the same small area of machair. This bird arrives on Tiree as early as 5 February but is back in Dublin Bay by the start of August, so splits its time roughly equally between Scotland and Ireland.

Most intriguingly, two colour-ringed Oystercatchers - one ringed in Ireland and one ringed in Wales - bred together on the machair at Loch a’ Phuill in summer 2019 and produced one fledged chick. Bird ZN was ringed at Sandymount Strand, Dublin Bay, Ireland on 22/11/2014 and spent the 2017 summer at Loch a’ Phuill. Bird AY5 was ringed at Bangor Harbour, Gwynedd, North Wales on 19/1/2014 and also spent the 2017 summer at Loch a’ Phuill, but the two birds were not paired, and ZN was seen back in Dublin Bay in the 2017/18 winter. In May 2018, the two birds were seen together at Loch a’ Phuill on two occasions but they did not appear to breed, and both birds were seen back at their respective ringing locations in winter 2018/19. In April 2019, it was clear that the two birds were paired at Loch a’ Phuill and they built a nest there, although this was unsuccessful. However, they re-nested and succeeded in raising a fledgling in July 2019. Hurrah!

ZN and AY5 together

Following the success, ZN was back at Sandymount Strand in Dublin on 10 August 2019 but was not accompanied by AY5, who presumably had returned to Bangor Harbour in North Wales (its colour-rings are increasingly hard to read).

The big question is where will their fledged Scottish youngster choose to spend the winter holidays – with its father in Ireland or its mother in Wales? Unfortunately, as the youngster was not colour-ringed, we may never find out which it chose!