“Throughout the seabird breeding season there were regular blogs mentioning the calm conditions, feeding frenzies as far as the eye can see and also an increase in numbers of most species from last year. We won’t forget that magical day in June where the sea was as flat-calm as glass, with feeding frenzies of auks, gulls and gannets out on the Forth as far as the eye could sea. All these things hint that it might turn out to be a good season, but as scientists we don’t like to rely on hints and want some good old solid evidence. This is where we seabird researchers, or scientists, from the CEH, come in. After four months of intensive fieldwork and another month of number crunching and lab analysis we can now reveal just how good the season was.
In fact, 2014 was the most successful season on record in terms of how successfully pairs bred for northern fulmars and was also good for kittiwakes and shags. Kittiwakes bounced back from a poor 2013 to record the best season since 1987. This is really important because kittiwakes are often the best indicator of the health of the seas around the May and are very vulnerable to poor fish availability. As a result they can show the wildest fluctuations in breeding success from year to year but 2014 was a bumper season with an average of almost 1.2 chicks per nesting pair, and with some pairs successfully rearing three chicks. For some of the seabird researchers who have been working on the Isle of May for a long time, the last time this happened is just a distant memory. Only two years have been more successful for kittiwakes, with the most recent being 1987- before some of the Fluke St residents were even born! Shags also did well with the fifth most successful year since monitoring began. Shag parents are able to raise several young in a season and we found one nest with four well grown chicks, which is exceptional.
We don’t just look at how many chicks the birds produce. One of our main tasks each year is to re-sight as many as possible of the individually colour-ringed seabirds to see how many birds survive over the winter. This was especially important this year because we had large numbers of seabirds, especially shags and puffins, die over the winter of 2012 to 2013 and we were hoping that we wouldn’t have another winter like that. In fact we found that the rate of return from the previous summer was average, which was great. This also meant that the low number of kittiwakes we saw last summer was not because these birds had died, but because they had skipped breeding and taken a year off in 2013, which is a relief.
People are really interested in looking at the timing of annual events, for example first frogspawn or first butterfly emergence, because changes in timings of such events have been linked with climate change. This is also true for our seabirds and so we are try and record the date each year when we see the first eggs of each species. We found that most species laid on typical dates this year, although shags, which are often more variable than other species, were ahead of the long term average. This was another sign that the conditions were good for the birds.
So, so far a great season. However, it was a slightly more mixed picture for the auks. Guillemots had a typically average year with 0.7 chicks raised per pair while Puffins were slightly below average which might have been due to the luxuriant growth of vegetation this year, hampering their efforts to access their burrows with food and giving the gulls an opportunity of an easy meal. The only real losers this year were Razorbill. This species had the fourth worst breeding season on record. The reasons for this are unclear, but if we continue to get a run of poor years then this could start having big negative implications for this species.
Clearly it has been a good breeding season for nearly all species which must have meant that there was an ample food supply but what was this food supply? From samples collected and observations made we were able to deduce that the birds were feeding primarily on sandeels and clupeids (mainly sprats). These are the most highly nutritional fish species in the region and the prey of choice for most of the seabirds.
There is plenty more work to be done through the winter to look in more detail at some of our results but in the meantime it is pleasing to reflect that the assorted observations through the season have shown that the birds have had a productive year and have hopefully entered the tough winter period in a good physical state ready to return to be observed by many on the Isle of May next year.
For more information on the CEH Isle of May study look up the website:
Mark Newell, Mike Harris, Sarah Burthe, Carrie Gunn, Sarah Wanless and Francis Daunt
Centre for Ecology & Hydrology, Edinburgh.