Friday, 4 September 2015

Kittiwakes on Rockabill, 2015

Now its time to catch up with our Kittiwakes! The most beautiful gull in the world according to many, and the only true 'sea-gull' that breeds in Ireland - all of our other species can be found inland, but these guys breed on seacliffs and forage out at sea. You won't find Kittiwakes in Roscommon or Carlow! 

A Kittiwake chick and adult. (picture taken under NPWS license)

Breeding Numbers: 
Last year we had 155 pairs, which was a bit of a relief after a major crash the year before! We would have been more than happy with something similar this year, and overjoyed with anything closer to 200 pairs. . . . . . . . . so imagine our delight when we counted 215 breeding pairs on Rockabill this June! Birdwatch Ireland have been carrying out surveys of many cliff-breeding seabirds in the Irish Sea this summer, and most Kittiwakes have declined since the last time they were censused. So though Rockabills Kittiwake population is small, an increase is still great news!

Clutch Size:
Kittiwakes generally lay two eggs, and that was no different on Rockabill this year with an average clutch size of 1.8 eggs - more 2's than 1's in nests, and a few clutches of three. Kittiwakes often travel huge distances over several days to source enough food to feed their young, so having two chicks is heding their bets a bit in the hopes that one survive. Anything else is a bonus, and those with three eggs are either very determined or very optimistic! To read about some recent research by the RSPB tracking breeding Kittiwakes in the UK click Here.

Clutches with 3 eggs are great to see - marine litter in nests is not great to see!

'Productivity' refers to the average number of young that survived to fledge for each breeding pair. On Rockabill, and in many other sites, this usually averages out around 1.0, which stands to reason with what I said above - most seabirds that lay two eggs are basically hoping that one of those two eggs goes on to have a chick that survives the season and eventually goes on to breed. This year on Rockabill our Kittiwake productivity was a bit below 1.0. It wasn't our worst year for productivity, and its not too bad as long as it doesnt stay this low in the long term. Kittiwakes are relatively long-lived and so one bad year every now and again isn't a disaster - they can make up for it in other years.

There are likely to be many reasons for this years poor productivity. One of them is certainly gull predation - some of the larger gull species hang out on the Bill during the summer, and can be quite opportunistic when it comes to food. Generally they're on the lookout for fishing boats they can follow and get scraps from,  but the bad weather made that a bit harder this year and so some gulls resorted to stealing Kittiwake chicks! Bad weather also played a more direct part. Early in the season some of the lower-down nests were simply washed away by strong southeasterly swells. Later on in the season some chicks will have been blown off before they were ready to fledge, and some new fledglings would have gotten into difficulty when flying as they were blasted by strong wind and rain. These are all natural processes, and as long as they arent happening every summer the Rockabill Kittiwakes should be ok!

Every year we do our best to ring all of the Kittiwake chicks on Rockabill, to help provide important information on the species down the line. This year we recaptured 7 adult Kittiwakes that were born and ringed here in the past and returned to breed - two were 12 years old and the others ranged from 4 to 7 years old. In addition, at the end of the season we spotted an adult Kittiwake with colour-rings that we suspect was born and ringed in France, but came to Rockabill to breed. We're still waiting for further details on that bird, but it shows the value of ringing and the kind of information it can yield (though it takes a few years!). To read more about ringing of Kittiwakes, see the BTO website Here.

Kittiwake fledgling. (picture taken under NPWS license)

So thats our update on "the most beautiful gull in the world" on Rockabill in 2015. For those of you keeping score, thats one species that had a good season (Black Guillemots) and another that had a fairly mixed year (Kittiwakes). Keep an eye out for more updates in the coming days!

Brian with an adult Kittiwake.

Kittiwake (left) and Andrew (right)......

Two first-year Kittiwakes.
Shade in short supply on the cliffs.
Some Black-Legged Kittiwakes dont have very black legs!

Adult Black-Legged Kittiwake - the most beautiful gull in the world!

No comments:

Post a Comment