David Scott PhD thesis

 David's PhD thesis is often quoted by anyone who writes about Stormies. At the time David did not have the time to publish any papers from his thesis and the thesis itself was 'old-school' i.e. still on paper so, for most, unaccessible. Over recent months Oxford University has scanned David's thesis and David himself has made it widely available to anyone who wishes to download a copy for free.

It is available at: https://ora.ox.ac.uk/objects/uuid:24973c21-ab78-42f1-a3c1-a7665b776bbf

Note that it is 35Mb in size (something like 300 odd pages).

A late recovery from this year

2757508 ringed on ENR on the 11.8.2021. was recaught at Score, Highland Region, seven days later having traveled 154km - a mere 22km a day, which is a dawdle by stormie standards.  

End of year bits...

Four stormies we caught on Nan Ron in August have now come back as new ringings all performed in July - so not really that interesting other than that they are still around after a month. We managed to add to data by sexing and aging two as 6Fs.

The Great Skua we resighted by colour-ring was a juvenile bird of this year too, and the one found dead, alongside the dead Greater Black-backed chick were also of this year.

A flood of recoveries

 Many recoveries we get of birds caught and/or recaptured on Nan Ron come about by the contribution of others. To date 46 other permit numbers have contributed to retraps or controls, from individuals to partnerships, ringing groups or observatories.

This flurry of recoveries is a combination of our work on Nan Ron and the work of the Bache, Shearwood and McShane Ringing Partnership (now Belvide RG) and Stefan Bodnar. Fifteen other permit numbers have been responsible for other ringing or recaptures of birds reported here.

This post reports seventy-seven birds caught and recaptured on Nan Ron. The four oldest were greater than 14 years old (5837, 5458, 5111, 5103 days between ringing and recapture) while another four were greater than 11 years old. The graph shows the time elapsed between ringing and recapture of these 77 birds. Twenty-two birds were within year retraps while 28 were recaught approx two years after ringing.

Two birds ringed this year in July were recaptured elsewhere: one at Fair Isle BO (19days and 189km later) and one at Score, Highland Region (10days and 154km later).

Thirty-one birds ringed elsewhere were recaptured (controlled) on the island. These ranged from seven birds all recaptured within a year from St Johns Point, Highland Region to one originally ringed on Priest Island 5867 days previous (c15 years). An interesting movement is abird from Collieston, Aberdeenshire to nan Ron, 196km in two days (although this is well within reported foraging distances for Storm Petrels). Any birds caught with an elapsed time of >1000days between ringing and recapture could be considered to be local breeders.

Note also the one bird from Cork, we don't get that many movements from Ireland, and one bird originally ringed on Skokholm in 2019.

The return on the retraps

Individuals ringed on Nan Ron and then caught again on the island are low. For many they constitute the young 'wanderers' - those birds of insufficient maturity to breed who pop in to investigate the lures as representative of potential breeding sites and then move on to prospect elsewhere. Other birds captured of an age greater than 3 years old are considered to be breeders.

Of the four birds caught this year in this category all four can be considered breeders.

Results have been received on another 26 birds that were originally ringed elsewhere, now caught on Nan Ron. The four highlighted could be considered as breeders as all are greater than 3 years old - and thus should be breeding. It is possible however that they could be failed breeders for the year who are 'wandering' to explore more potential succesful breeding sites. 

And the Stormies.

 Firstly we were here to capture and ring Storm Petrels. In previous years we have targeted numbers - catching as many as we can because so little it still unknown about these little seabirds. This year we wished to slow down a bit and take more notice of the birds in our hands. Ageing and sexing Storm Petrels is a bit of a black-art open to a fair degree of subjective assessment. We wanted to see if we could add to this arguement. 

Second we want to try and understand how many Stormies use Nan Ron and how big the breeding colony(s) across the island actually are.

Ringing: Scotland being what it is we lost two nights of ringing, one to rain and one to gusty winds. We still had a 'night-out' with the gusty winds having a camp fire (without the fire) viewing the stars and Milky Way and watching the Perseids meteor shower.

The quick ones among you will know this is not Nan Ron - the tree is a give away.

Photo from www: https://www.almanac.com/content/perseid-meteor-shower

At the end of our visit we ringed 608 new birds with 68 retrap (all UK ringed birds). Nine of these birds were our own retraps from previous nights' ringing.

Of these new 608 birds 233 were processed for biometrics and closer inspection. We took wing lengths, weight measurements and inspected the shape of primary (number 10), for ageing, and the extent of white on the underwing, for sexing. We also recorded whether the bird had vomited, evidence of breeding (bringing food to young), had any foot loss, indicative of age, and whether they had a brood patch, which is evident in breeders and pre-breeders (inexperienced birds getting ready to breed).

Using the extent of white underwing for sexing we also took photos. The image below shows bird 2757487 which appears to be female - poor extent of white (in simple terms). However, we will need to go back and revisit this as we found that the strength of ones head torch very much influenced the (apparent) extent of white seen.

The shape of primary 10 (P10) needs reviewing as we had some birds of known age who 'appeared' to be much younger - P10 pointed instead of round. The brood patch presence, and its significance, needs more thought as every bird - all 233 - had a brood patch to some degree. For those birds caught without sound lure this would be expected /anticipated, but at least two-thirds were caught using a lure when we would have expected a higher percentage catch of non-breeding wanderers (and therefore no brood patch).

Still much to do (and learn).

Census: a detailed 'call-back' study was undertaken of most of the walls - they look ideal nesting sites. Surprisingly there was nothing! However, once we had sat and thought about it we considered that, maybe, because this was also the Barn Owl foraging area (it nests in one of the old buildings) that maybe they had been forced from this area. We next censored some of the rocks and gullies on the north of the island. Not only did we get call-backs but we also got:

An egg with a sitting bird (or at least a bird close by, later ringed, on two seperate days). This confirms breeding - only the second actual egg discovered in recent times. The egg date may be considered late but Stormies do have an extended breeding season with some chicks not leaving burrows until October. This egg may be a second attempt from a failed experienced breeder or the first egg of a newly breeding female. Next year we hope to censor the island in greater detail in this respect.

Of other birds a previous group had ringed all of the Bonxies - or so they thought - we still managed to ring two (one a young bird, one old) and we found one chick dead. Of the Greater Black-backed gulls ringed we also found one of these dead. During the fulmar census we came across a wandering, single, juvenile Greylag Goose - this went unringed as it appeared to be without parents and thus unlikely to survive. 

The end of another year - we'll be back. 

The team this year:

Steph (playback expert), Gerry (moths and springtails), Kenny (Nan Ron old hand and seawatcher) Jean (our ever dependable route to the island), Bob (data collector and lichen prospector), Alison (newbie, swimmer and yoga guru), Bekka (newbie, swimmer, biscuit hoarder and all-round helper), Liz (helped with the fulmar census, swimmer and kittiwake expert - pity there are no kittiwakes).

All apart from Jean are BTO registered bird ringers with Gerry and Bob holding S permits and appropriate endorsements. Everyone collected skua pellets.

The visit of 2021

 It was good to be back.....

...fortunately the island looked very much as it did before - the sheep were still there and the buildings still standing. The island was 'dry' with vegetation having grown little with, fortunately, very little signs of 'the midge!' As it was dry there was little evidence of sundew (we said we'd look for it) although butterwort was present, as were the orchids. This year for some reason there was a noticeable increase in the numbers and variety of mushrooms.

The sheep were still roaming about with lots of youngsters while, at the other end, a few signs of old age death. One unfortunate, near the camp site, had to be moved a little further down-wind.

There had been changes though - brought about my two winters of absence - with some rock falls causing noticeable differences. At the end of what we call, The Gully, there had been some movement which, after a scramble, gave a view of the Arch - which wasn't possible previously.

This year a team of seven eventually found itself on the island (thanks to Jean) with a few late drop-outs due to ill health. We had a hardy nucleus with us as some ventured a sea swim - on more than one occasion. 

Although we were on the island for the Storm Petrels we did do other things. We set a moth trap, performed a fulmar survey of the island (numbers much reduced on 2019) and undertook a play-back lure census of Storm Petrels around the buildings and at various other sites on the island (next post). We also collected every Bonxie pellet that we could for plastic ingestion analysis. Although the Barn Owl was still on the island (seen) we could find no evidence of any pellets. We also sampled for springtails and spiders - because we could - and started to catalogue the lichens, both on the buildings and rocks.

...at last, the visit in 2021 gets closer.

Already two groups of others have visited Nan Ron in order to ring Storm Petrels. Our visit gets closer, with much anticipation following our Covid induced absence of 2020. So far twelve are billed to attend with four being new to island and nocturnal ringing. 

This year, following a small grant from the Seabird Group <www.seabirdgroup.org.uk> we shall be undertaking some stormie sexing studies, in addition to our usual biometrics and ageing. Sexing of storm petrels is 'challenging', to the extent that many do not undertake it, and ageing is subjective, so again missed. It is our hope that we can produce some guidelines and morphometrics (including photographs) to enable the ageing and sexing of storm petrels around the latitudes of northern Scotland.

....Barn Owl still eating...

 The ringers from Belvide have visited Nan Ron over the last week or so. Averaging about 300 new birds a night with about 20% more due to retraps, including some Norwegian ringed birds, they also collected some Barn Owl pellets and looked for rings. They found nine Storm Petrel rings of birds originally ringed on Nan Ron - in 2006, 2012, 2013, 2015, 2016(3), 2017, and 2019. If convention is followed all of the birds, except the bird from 2019, must have been adults breeding on Nan Ron.

So the Barn Owls are still present on the island, and they are still eating Storm Petrels as part of their diet. Hopefully, might be able to update this.....

A new year, hopefully with another visit

 Three new recoveries just received. All three birds were ringed on Nan Ron over the period 30Jul-2Aug 2019 and strangely, probably indicating they are all wandering juveniles of non-sufficient maturity to breed, all were re-trapped at Twinyess, North Ronaldsay on;

25 June (2757196); 10 July (2749012); 14 Aug (2757109). Needless to say 'distance' was the same for all, 141km, but days between capture and recovery were 328, 346 and 379 respectively.