Thursday, 29 March 2012

Reverse migration of 'west Atlantic' Brent to Ireland

Following reports of an odd double-metal ring combination on a pair of Brent in Dublin, observations of which were made several times, Graham managed to get to the bottom of the mystery thanks to our Canadian colleagues Sean Boyd and Kathy Dickson.
These birds appeared to have a metal (steel) ring on one leg and an aluminium ring on the opposite leg which made them unusual.
The birds were observed at several Dublin locations between 20th November 2011 and 28th March 2012 and it turns out they were probably banded on Baffin Island.

Canadian biologists have been studying this "Atlantic" population which breed in low-arctic Canada and winter on the eastern seaboard of the US (example the 'banana-eating Brent at Queen's New York in the previous blog post'), banding birds on the Great Plain of the Koukdjuak, Baffin Island, or on Southampton Island further west in the Foxe Basin. The fact that the birds appeared to be a pair makes it most likely they were banded on Baffin Island, where pairs and family groups are the target of banding activities (at the Southampton site the majority of birds are non-breeder moulters, but may also include failed breeders).

Lest you think that fitting two metal rings was an accident (and it sometimes happens!) we are advised that 'double-banding' Brent at these two sites has been done intentionally as part of a study to determine band loss rates by comparing regular aluminum bands to stainless steel.

Thanks to all keen-eyed observers involved, the diligence of getting to the bottom of the story (Graham) and the information from Sean and Kathy. As Sean says we can all sleep easy now :-)

And here is a picture from Cian which apparently he is embarrased about. It would take an exceptionally good picture to be able to distinguish these 'Atlantic' Brent from our 'Irish' birds but the rings give the game away - it would be interesting to know how many and how frequently low Canadian Arctic birds head across the Atlantic in the winter. We certainly know now that it does occur!

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