Monday, 31 July 2017

'PUL' the other one!

An important part of our work in Dublin Bay involves the ringing of key waterbird species to learn more about the birds and how they use Dublin Bay. As well as providing us with important information on their usage of breeding/feeding/roosting areas within the bay, we also get some very interesting ring resightings of ‘our’ birds from further afield – some of the Terns we’ve ringed in Dublin Bay have been resighted in Scotland, Wales, Northern Ireland and on migration in Namibia!

Common Tern - the most numerous Tern in Dublin Bay. (BB)

For the terns, these resightings are largely in line with what we’d expect – we’d expect the terns that breed in Dublin would be using parts of the Irish coast on migration and eventually end up in Namibia. We’d also expect that the majority of the Terns that roost in Dublin Bay after the breeding season might be from different parts of Ireland, or colonies nearby in the UK. Though somewhat expected, this is still all very useful information to collect from a conservation point of view! That being said, we do enjoy some of the more ‘novel’ and unusual sightings – so imagine our delight when we got an email from Oddvar Olsen in Norway!

Enclosed in the email was the picture below of yellow ring PUL – a ring we had put on an adult Common Tern at Sandymount Strand in south Dublin last August. Sandymount gets several thousand terns in August and September each year, roosting in the evenings for the few weeks between leaving their breeding site and setting off on migration for African waters for the winter (it's quite the sight on a late summer's evening!).

Colour-ring PUL - put on a Common Tern at Sandymount Strand last Autumn.

PUL was caught in Dublin last Autumn, but won't be back this year! Ring found at Raudholmane in Norway this year.

Now it’s always great when someone accompanies a resighting with a picture, so we can be absolutely 100% sure that the ring was read correctly etc. That being said it’s less great when there’s no bird in the picture… 

Oddvar found our Common Tern ring while investigating causes of decline of Black Guillemots along the Norwegian coast. The ring was  close to the nest of a Great Black-backed Gull. 

Great Black-backed Gull - the largest gull in the world (BB)

Great Black-backed Gulls have a very flexible diet, that often includes young seabirds at this time of year – those that aren’t great at flying take a few seconds extra to take off and they aren’t as manoeuvrable in the air. An adult Common Tern like PUL is a much trickier meal though – these ‘Sea Swallows’ are skilful and pacy flyers compared to a lumbering GBBGull. I have found the rings of adult terns myself near GBBGull nests and roosts though – sometimes the Tern might have been sick or injured, and sometimes the GBBGull might just get lucky! It’s all part of the circle of life and has been going on for thousands of years. In recent times us humans have been disrupting the natural order by destroying the habitat, nesting sites and food sources of terns and gulls alike – that’s where the problem lies! The resulting effects are felt throughout the seabird communities and wider ecosystem biodiversity around our coasts.

Great Black-backed Gull. (BB)

In the coming weeks our Dublin Bay Birds Project staff and I-WeBS team, along with some very dedicated volunteers, will be counting and recording roosting Tern flocks around the country. We'd very much appreciate records/counts of tern flocks from around the country - full details here:

For anyone who thinks they might have spotted one of our Dublin-ringed Terns, please enter the details of the sighting here and we'll get back to you:

Keep an eye out for the next blog later in the month!

- Brian B

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