RSPB Seabird Surveyor, Thalassa McMurdo-Hamilton, gives us an update on the Orkney seabird breeding season.
Dramatic seabird breeding failures in Orkney for another season
Welcome to the second Orcadian seabird blog (to read the first blog click here). This past month has been full of ups and downs for me as a seabird surveyor. This month, it’s been all about guillemot, razorbill and kittiwake chicks: hatching, survival and fledging.
We’ve expanded our productivity monitoring to razorbills and shags. Shags appear to be doing well, with many fledged young visible along the cliffs at the moment. I’ve also learned that razorbills sit even more tightly on their eggs and chicks than guillemots. It makes for some long watches but it’s worth it when you get a glimpse of a chick beak poking out from the top of the adult’s wing! From both plots, I’ve had a few successful jumplings but it’s a mixed picture for this species and one that won’t become clear until the end of the season, or even after a few years of monitoring.
A razorbill brings in some sandeels for a young chick, at Marwick Head.
The same chick, a bit older and close to leaving the cliff ledge, looking like a mini adult!
Guillemots are also struggling and it is shaping up to be a disappointing season. There has been quite a bit of variation between the colonies, for example, chicks began to hatch a whole week earlier on the east coast than the west coast. At Mull Head in the east, from a total of 70 pairs, less than ten chicks fledged, and the breeding tailed off dramatically towards the end leaving the cliff face empty of auks by mid-July. At Marwick Head in the west, after losing three-quarters of the guillemots on eggs within around a week, I had only one small shelf left. The birds there hung on, and with seven medium-large sized chicks, I had high hopes! In the end, only 6 chicks fledged out of 63 pairs.
At another unmonitored location on the east coast, I was lucky enough to see 6 guillemot chicks leaving the cliff ledges! They had some loud encouragement from an adult below, and sometimes a bit of a tap on the head as encouragement on the edge.
This year we have spent some time looking at how often food is brought to the guillemot chicks and what type it is. It’s really enjoyable as I get to see lots of fascinating behaviours and I always enjoy seeing food coming into the colony. Recently, I saw a guillemot coming in with a display fish. However, it seemed the perfect size to feed a growing chick and attracted quite a lot of loud attention from the brooding adults. Eventually it was wrestled out of its beak, but dropped to the ground on the ledge. One smart parent clocked it very quickly, picking it up off the ground and feeding it quickly to its chick. Even the interesting behaviour was not enough to distract me from the fact that very small amounts of prey were being brought to chicks.
My final ledge of guillemots at Marwick Head that I grew quite attached to – can you tell which ones are brooding chicks?
There really is no good news for the kittiwakes this season. The seriousness of the situation is making everyone take notice and you may have heard me talking on BBC Radio Orkney earlier this month. Kittiwakes becoming media darlings is not enough to rescue the situation however and after a very slow start, few pairs laid eggs and even fewer made it to chick stage. At this point in the season (late July) even large colonies with almost 100 pairs have been reduced to less than 5 birds. Although it was predicted that this year would be bad, it is still very sad to see so many empty nests.
A deserted colony on the Brough of Birsay which holds just one nest with kittiwake chick in mid July (marked by red circle).
Why are kittiwakes and guillemots doing so badly? These species are sensitive to prey quality and availability. Kittiwakes are surface divers and cannot access the wide range of food in the whole water column that other species can. Guillemots, despite being able to dive up to 60m to find their prey, can only carry one prey item at a time. Therefore if the only prey they can find is small or of poor quality, they cannot make up for this by carrying more food. Due to rising sea surface temperatures around Orkney waters, breeding seabirds’ key prey item, the sandeel, is simply not found in high numbers anymore. It is believed that poor food availability is the main driver of the long-term seabird declines in Orkney – it’s not just kittiwakes and guillemots that are suffering.
I will be writing again soon to summarise the year, including a fulmar update and the final outcome of the kittiwake season. In the mean time, there are still plenty of beautiful wildflowers along the cliffs, as well as amazing behaviours to be observed, so put your boots on and admire our coastlines – they may look very different in the years to come.
Eyebright
Marwick Head in sea fog – a landscape that may fall silent in years to come.
All photos by Thalassa McMurdo-Hamilton