Wednesday, 25 June 2014

Rockabill Nest Census 2014 - Roseate Record Reached?

So we've been a bit quiet on the blog over the last week - sorry for that - though some of you might have seen/heard us on the RTE Six-One News on Monday and The Star tand 2FM today, proving that we're alive and well! The reasons for the lack of regular updates have been twofold - the first being that the huge number of eggs we alluded to in previous posts are now turning into huge numbers of chicks! So that means we have hours of counting, measuring and ringing to do every day. It's amazing to see how quickly the chicks grow, how they interact with their siblings, and how protective their parents are - but it's also tiring trying to keep tabs on all of the above!

The other reason for the lack of updates is because over the last ten days or so we carried out our full-island nest census - seeking out and counting every single nest and clutch on the Rock and the Bill, and repeating the whole thing again a week later. To say that it was exhausting would be an understatement, but from all that hard work we can tell that it's looking like a pretty good year on Rockabill. The results are still provisional at the moment (we have one of the Roseate Terns crunching the numbers for us again...), but here's what the breeding numbers for each species on Rockabill this year look like at the moment:

Roseate Tern - the Rockabill breeding population has increased slightly this year, which is good news for the species in Europe! (Picture taken under NPWS license)

 Roseate Terns
First of all it bears repeating that the Roseate Tern is one of the rarest breeding seabirds in Northern Europe. Rockabill is the single biggest breeding site for Roseate Terns in Europe and we have around 80% of the Roseate population of Ireland, the UK and France here on this one little island, so needless to say what happens on Rockabill is pretty important! A lot of hard work has been put in over the last twenty-five-plus years and for much of that time the population here has been increasing - from 180 pairs in 1989 to over 1,200 in 2013 -with numbers levelling out over the last few years. This year we're happy to report that it has again been a good year with close to 1,250 pairs of breeding Roseate Terns - a new record that's slightly above last year's total. It's a small increase, but good news nevertheless! Nestbox usage has been good again, with a large number still going for more natural sites in the shelter of vegetation, rocks or in between nestboxes!

Common Tern - very common on Rockabill! (Picture taken under NPWS license)

Common Terns
As with the Roseates, the number of Common Terns has been generally increasing for the majority of the last twenty-six years and remained in the region of 2,000-2,200 pairs in recent years. Well we're happy to report that we have close to 2,150 pairs this year - not a Rockabill record, but very good all the same and more good news for breeding Terns and Seabirds in Ireland this year.

Arctic Terns
Arctic Terns have always bred here in smaller numbers than the others - they breed in bigger numbers on the west coast. In 2009 there were over 350 breeding pairs here, many of which were located on the Bill, but they have declined dramatically since. Unfortunately this year the Arctics have been the victims of repeated predation by Herring  Gulls and there are few if any left on the Bill, with the smaller colony by the helipad suffering a similar fate. We suspect a small number of pairs may be scattered around other parts of the island, but it remains to be seen how successful they will be.

Severe storms over winter have had a devastating effect on our Black Guillemots. (Picture taken under NPWS license)

Black Guillemots
On our first week here we got up at 7am every morning to count the number of Black Guillemots on and around the island to give an indication of how many were likely to breed here over the summer. Unfortunately the severe storms over the winter had a pretty devastating impact on our Auk species (Guillemots and Puffins) and a number of Black Guillemots born and ringed on Rockabill were found dead along the coast in Dublin and Northern Ireland. As expected their numbers are way down this year with only around 50 pairs breeding here, compared to 90 or so nests for each of the last three years. Fingers crossed most will manage to successfully fledge young this year, and that the coming winter is better than last - though with extreme weather events expected to be more common as climate change progresses, it's hard to predict how populations of species like Black Guillemots will fare here in the future.

Kittiwakes in "Kitti-City" on Rockabill. (Picture taken under NPWS license)

So far we've had good news regarding Roseate and Common Terns, and bad news about our Arctic Terns and Black Guillemots - what about the Kittiwakes? Well they're doing ok - they've had better years but they've had much worse too! We have around 150 pairs this year. Numbers last year were low, but our count this year is not too different to most of the previous year's. From our census it appears than the average clutch size is a little higher than expected, so hopefully that bodes well for the future.

So that's the (provisional) results of our nest census on Rockabill for the 2014 season - the good, the bad, and the! It's important to remember that those counts are just of nests and breeding pairs - this isn't the end of the story. The chicks have started to hatch over the last week and it'll be late next month before they'll fledge, and needless to say a lot can happen over those few weeks - predation, disturbance, food shortages, disease and (probably most significantly) severe weather might all yet have  say in whether or not 2014 is considered a good/successful year for the breeding seabirds on Rockabill. But so far so good!

We'll keep you updated! In the mean time, spare a thought for us during what is the part of the breeding season that all of those Common Terns are at their most aggressive!

 - Brian & Donnacha

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