2019's seabird survey report has now been completed and is just going through its final checks before publishing. It contains lots of fantastic information and data collected and crunched by our Seabird Ecologist, Vickie, with the assistance of the Rangers. Back in July 2019 we published an interim update with information regarding Puffins, Gulls and Kittiwakes; now we've got a bit more to share!

This work is kindly part-funded by DEFRA through the Isles of Scilly AONB 


From April to September each year Seabird Ecologist, Vickie, rejoins the Isles of Scilly Wildlife Trust Team to begin the annual routine seabird surveys across our Islands.  Starting in late April with the breeding population of the iconic Scilly Puffin, before the non-breeders return to the Islands in June, and concluding with the Manx Shearwater & Storm Petrel fledgling chicks in late September.

Surveying takes place throughout the breeding season, with regular return visits to a number of colonies, recording both breeding numbers (pairs) and productivity (number of eggs, number of chicks, number of fledglings) using a variety of methods.  During 2019 we also carried out a little investigative work (using trailcam recording equipment) to try and discover what, or who, was having an impact on some of our breeding colonies (including our colonies of Lesser black-backed gull, Kittiwake & Storm petrel).  

Some of this information was published in our interim update in July (Scilly's Seabird Surveys So Far ~ Successes & Surprises) but this was written before survey work on Fulmar, Manx shearwater and Storm petrel had been fully completed, so there's still plenty to tell you! 


Middle of the Season:

Kittiwake Chicks ~ Photo : Natalie RanceOur interim update left off in June with the shock finding that our Kittiwakes were failing as a result of the Peregrines and that the Gulls were actually acting as Bouncers and protecting them!  However, the Peregrines were seen to be using the low sun, early morning and late evening, to disguise their approaches and sneak under the Gulls' radar too. 

At the time of writing Scilly's Seabird Surveys So Far ~ Successes & Surprises there was one remaining Kittiwake chick and we were unsure what would happen; Seabird Ecologist Vickie hoped that the little white ball of fluff had reached a large enough size to no longer be at risk, but we really weren't sure. 

Fast forward a few weeks and it seems that the little fuzzball was big enough and we are fairly certain it fledged! 

Outcome:

During 2019 the Kittiwakes only bred at one site (that we know of) on the east side of Gugh and a total of 20 pairs were counted on nests.  From the last week of April a camera, supplied by Dr. Tom Hart of the Oxford University Seabird Watch team, was set up at the Kittiwake colony.  Despite the small numbers of birds at the colony they appeared, initially, to do well; with adult attendance at the nests sites high and the first newly hatched chick seen on 19th June.  Sadly, we now know that the majority of the chicks perished as a result of Peregrine predation; however, it does appear that one chick escaped the Peregrines and fledged in late July! 

This puts breeding success for 2019 at just 0.05 chicks per pair; although low this is up on last year where the colony failed completely.  Our breeding Kittiwakes have suffered a 93% drop in numbers and a total breeding failure in 7 of the last 14 years. Even though the primary cause of failure this year was predation, the reasons behind this are many and varied and could range from human disturbance to changes in weather patterns, changes in food availability to time spent away from nest sites all leading to predation being successful. 

We hope to be able to continue our investigative work during 2020 and beyond to try and discover more answers, so we can assist our Kittiwakes to successfully breed again in seasons to come.


Moving through June and into July we added Guillemots, Razorbill, Manx shearwater, Storm Petrel & Fulmar to our survey, checking breeding numbers before beginning on the majority of our productivity survey visits in August; starting with the awesome Fulmar towards the end of July.

These beautiful, charismatic birds are a "relative "of the Albatross, and as such ordinarily spend most of the year in the open ocean.  That being said they can be seen in Scilly all year round and are one of the Teams favourite feathered sea-critters!  Records show that the Fulmar first began nesting in Scilly in the 1940's and our current breeding populations are relatively stable and healthy.

Survey work around Scilly Fulmars concentrates on two key areas of cliff where they nest; on Menawethan and near the Daymark on St Martin's.  These areas are monitored and surveyed from the sea because it is the easiest and most effective way, due to the very nature of their nest sites. 

This years surveys saw 87 nests recorded across the two sites and fledgling successes (productivity) of between 0.38 and 0.53 chicks per pair.

Outcome:

Fulmar numbers are stable within the Islands and breeding success rates, following an overall low of 0.16 chicks per pair in 2014, now appear to be following an upward trend.  We are hopeful that this will continue in coming years and numbers may reach the 0.5 chicks per pair it's estimated are needed for their ongoing colony stability.  


We also continued with the other "comedy" element of our survey work, focusing on the "burrow-nesters"; whereby our Seabird Ecologist and Rangers are ordinarily seen head down, bum up apparently making strange noises and looking like they've assumed a bizarre sleeping position. 

With their heads near, or sometimes in burrows and crevices, what they are actually doing is playing recordings of either Manx shearwater or Storm Petrel and listening for "call-backs" sometimes from adults at this time of year, but sometimes from chicks too!  These surveys take place across the whole archipelago, including St Helen's, St Mary's, Tresco, Bryher, St Martin's, Annet, St Agnes & Gugh.  Although our main focus is on Annet and St Agnes & Gugh and the birds that are successfully breeding, thanks to lack of mammalian predators on these three Islands.

During 2019, 27 AOBs (Apparently Occupied Burrows) were recorded on St Agnes with an additional 42 AOB's being recorded on Gugh; these are burrows that have adults in them during the day, suggesting that they are potentially incubating eggs.  We also encountered something we had not seen before, two undamaged Shearwater eggs outside burrow entrances from which birds replied; possibly suggesting that the previous owners, and their unhatched offspring, had been kicked out.

Moving into late August and early September we started night-time "chick-checks" across St Agnes and Gugh and from the 69 AOB's recorded during the call-back surveys 45 "star-gazing chicks" were found (13 on St Agnes and 32 on Gugh). 

Sadly, the Shearwaters & their offspring didn't fair so well on other Islands with evidence of adults and chicks being predated on, and little indication of fledgling success other than one lonely "star-gazing chick" being found on Peninnis during mid-September.  This chick was of a good size and still being fed by an adult bird, when it was seen, so it is highly likely that it survived to join the ranks of other newly fledged chicks when they left the Islands to migrate. 

Outcome:

Since the removal of rats from St Agnes & Gugh in 2013|2014 the number of "star-gazing chicks" recorded from these two Islands has increased from 0 in 2013 to 45 in 2019; as you would expect with an increase in chicks there has also been an increase in the recorded number of adults in burrows too, from 22 in 2013 to 69 in 2019. 

It would appear that these increases in numbers are also meaning that there is a bit of competition for burrows (given the two ousted eggs discovered this year) and that numbers of birds attempting to breed, and in some cases successfully breeding, on other Islands are also increasing.  So another successful year for our Manxies!


And finally....

We come to the Storm petrels!  Scilly is internationally important for these miniature marvels and since the removal of rats on St Agnes and Gugh they have started to successfully breed there once again.  Our survey work on this species focuses on the birds that breed on Annet, and also St Agnes & Gugh and 2019 was definitely a year of two halves for them in terms of success and failure.

Our survey and monitoring work saw further increases in the number of birds at our "study beach" on Annet (this is a section of the Island that we survey every year, in the years that full island surveys do not take place), suggesting that Storm petrel are probably doing well across the whole of the Islands.  We again saw an egg out in the open, which could suggest that some competition was occurring over nesting sites.  

Storm Petrel tend to nest in crevices on boulder beaches and as such locations and formations of nesting sites can change quite drastically from year to year (particularly when we have fairly hefty winter storms and seas move even the largest boulders around with ease).  Our original study beach on Annet, where data was collected between 2010 and 2014, was completely destroyed by the storms of February 2014, so a new study beach was identified and has been used since this time. 

Numbers of AOS (Apparently Occupied Sites) are identified and recorded in a similar way to Manx shearwater surveys, with recordings of adult "Stormie" calls being played into crevices on the boulder beach; responses are then recorded.  Within our survey site on Annet 2019 was a bumper year with 338 AOS being identified, which is a huge success!

In terms of the failure, this came from our St Agnes and Gugh breeding sites.  Storm Petrels returned as a breeding bird to St Agnes and Gugh in 2015 following the removal of rats and since this time have been largely successful, with numbers seeming to increase year on year.  In 2018 there were as many as 20 AOS estimated from playback surveys at one site on St Agnes & Gugh; with most of our other seabird survey results for 2019 providing either stable or increasing breeding population numbers we were hopeful for a similar trend with the Storm petrels.

However, during July we started to discover a large number of wings and feet, from predated Stormie adults, next to the main section of a boulder beach known for a breeding colony; we questioned whether this could have been Peregrine related given the plight of the Kittiwakes, but the MO didn't seem to fit.  There was nothing for it but to put out trailcams to try and discover what was going on! 

The trailcam was deployed and then we just had to wait and see if the downfall of the Stormies would make itself/themselves known; it was a couple of weeks and a few more remains later before the culprit was captured on camera, but in the meantime we were kept entertained by the locals! 

Towards the end of July we captured footage showing the individual responsible for the Stormies downfall at the St Agnes breeding colony (no it wasn't this young chap, although we did find this highly entertaining!); the footage captured a cat actively hunting and eating the birds.  Another mystery solved during our 2019 seabird surveys!

Outcome:

So, a tale of two halves for our Storm Petrels.  The numbers nesting and fledging on Annet are continuing to show an upward trend, which would indicate an overall increase in breeding pairs across the Islands; this would also seem to be backed up by the "evidence" left behind from the number of birds, sadly taken by a cat, at the St Agnes breeding colony.

Work is continuing to take place in, and with, the St Agnes community regarding this newly acquired knowledge and we are hopeful that the Storm petrels will continue to do well across the Islands, and fair better on St Agnes, during the 2020 breeding season.


And that, as they say, is a wrap!  The 2019 seabird breeding season across Scilly has had its highs and its lows; we've made some interesting discoveries thanks to the wonders of modern technology, and now discussions are taking place regarding the best way(s) forwards and what we can do as a community to encourage and protect our important breeding seabird populations. 

The Seabird Monitoring and Research Project 2019 report is currently being proofed and double checked, once this is done and it's been signed off it will be available to read in it's entirety in the Technical Reports section of our website.


All images © Isles of Scilly Wildlife Trust ~ thanks to Communications Officer | Nikki Banfield; Marine Ranger | Natalie Rance and trail cam footage collected from Seabird Ecologist | Vickie Heaney