Part of our wardening job at the moment is to ring all of the chicks that have hatched - that is to put a small metal ring on their legs so that they can be identified later on. We're currently carrying that out across the island with the help of Dr. Steve Newton (BWI Senior Seabird Conservation Officer, and our boss!) and Mr. Ricky Whelan (Dublin Bay Birds Blog fame!). Common Terns get a BTO ring with a 7-character code (e.g. ST234575) on their right leg, and Roseate Terns get a BTO ring on their left leg and a special ring on their right leg. The special ring has a 4-character code (e.g. CF98) repeated twice on the ring which is easier to read than the BTO ring and thus makes it easier to gather data on this high priority species. The Roseate Terns from Lady's Island in Wexford are ringed in a similar way, except the BTO ring is put on the right leg and the special ring on the left leg - so if we see a Roseate with a special ring on its left we immediately know it's not from Rockabill.
|Roseate Tern with a BTO ring on it's right leg, and a 'special' ring on it's right leg. (Picture taken under NPWS license)|
At the moment the rings are very handy in identifying chicks - given how much they run around, hide and get mixed up with other chicks it means we know which chick we're weighing and measuring every day. Before the chicks hatched we spent several hours each day reading the rings on the legs of adults using a scope, which helps us gather data on the age profile of our breeding population, the survival rates of Terns that were ringed on Rockabill, and the immigration and emigration rates of birds born elsewhere breeding on Rockabill and vice versa. For example thanks to annual ringing efforts we know that a small percentage of breeding Roseate Terns in Lady's Island in Wexford were born on Rockabill, and a few Lady's Island born birds end up breeding here - and there's a much lesser rate of exchange of birds between Rockabill and Coquet Island in the UK.
All of this is useful data to help inform the conservation of Roseate Terns on Rockabill, and in Ireland and Europe, and hence we try and ring every single Roseate Tern and as many Commons as we can each year. Every now and again you get some very unexpected and interesting information from ringed birds however - the bird in the pictures below was ringed on Rockabill as a chick two years ago, and seen this year in Iceland!
|A Rockabill Roseate in Iceland! Only the 2nd record of the species in Iceland. (Picture taken by Yann Kolbeinsson)|
Now Roseate Terns carry out huge migrations each year, crossing many countries, but their journey takes them south to Africa - nowhere near Iceland! Roseate Terns are really considered a 'tropical' bird more suited to places like the Azores and the Indian Ocean, so the fact that we have them in Ireland is special enough - but that this one turned up in Iceland is very unexpected! It's only the second record of the species in Iceland, and was followed by a sighting of another Roseate Tern in western Iceland which was also born and ringed in Ireland (though the rings havn't been read yet - read about it Here). It often happens that birds get blown off course and end up in countries where they aren't native - we get a few American and mainland European birds blown to Ireland every year - but the question as to where exactly they came from usually remains a mystery. A big thanks to Gunnar Thor Hallgrinmsson, Yann Kolbeinsson and Sölvi Runar Vignisson for taking the time to read the rings and get in touch about their sighting!
In addition to that, in recent years Rockabill Roseates have turned up on a lake in Switzerland, a marsh in Central Poland and on the River Seine in France - none of which normally have Roseate Terns!
So ringing the Terns on Rockabill provides us with important information for the conservation from year to year, and occasionally allows us to shed some light on some of their more interesting adventures!