Monday 28 January 2013

Long Term Volunteering on Skomer and Skokholm 2013

There are currently opportunities on both island to help with the management of Skomer and Skokholm.


Sometimes you may be needed to give guided walks
Skomer and Skokholm wouldn't be what it is today if it wasn't for the hard work of volunteers. Weekly volunteers (on Skomer only) are handy for assisting with manning various points on the island, general maintenance and providing exceptionally high quality banter!

Maria carrying out vegetation transects

Long Term Volunteering is an opportunity to take this one stage further. With the long term volunteering placements we ensure that the successful applicant receives a bit more training but will also be given more responsibility. Each volunteer will also be responsible for some aspect of monitoring (could be anything from seabird monitoring, ongoing bird migration watching, butterfly transect, or a project which utilises your own specialism). All these skills (responsibility) are essential when trying to build a career in this highly competitive sector. We shall provide you with transport to the islands, wildlife trust t-shirts, first-aid training, accommodation. You will need to provide your own food and a willingness to learn.

What are the previous Long Term Volunteers up to (all thanks to Skomer of course!!;o) )?
Nia Stephens - Went to work for two seasons on Ramsey Island (Assistant Warden)

Aaron Davies - now does ecological consultancy.

Andrew Lawtone - Went onto to be a Trainee Curator in Manchester Museum.

Good opportunity to fine tune some skills.
Ali Quinney has returned to study fer final year in a B.Sc. Marine Biology and regularly uses Skomer in various case studies and presentation.

Leighton Newman - returned to university and hopes to come back over the next few years to use Skokholm as part of his dissertation.

Lucy Rotherwell - Now works for a Comedy festival in Australia as a Marketing guru.

James Roden - Returned to study Countryside Management at Aberystwyth and will be coming back to Skomer in 2013 for a longer placement and to carry out his dissertation fieldwork looking into the association of moths with different habitats on the island.


Thursday 24 January 2013

Manx Shearwater Whole Island Census results 2012 - >300,000 pairs

Extracts from: A whole-island census of the Manx Shearwaters Puffinus puffinus breeding on Skomer Island in 2011 SEABIRD 25 (2012): 1–13 

Authors: Chris M. Perrins, Matt J. Wood, Colin J. Garroway, Dave Boyle, Nick Oakes,
Rose Revera, Phil Collins and Chris Taylor

Skomer Island, Pembrokeshire, Wales is believed to have one of the largest colonies of Manx Shearwaters Puffinus puffinus in the World. In 1998 a census was made of the whole island, and the adjacent islands of Skokholm and Middleholm, in order to try to establish the size of the breeding population; the Skomer population was estimated to be just over 101,000 breeding pairs. A second census was carried out in
2011. First, a set of study burrows was opened and a tape of the male call (normally only males respond to these) was played down each burrow several times during the course of incubation in order to establish the male response rate. Then the same tape was played down all the burrows in each of 288 randomly selected plots across the island and the number of responses recorded. Extrapolating responses from census plots to the whole island yielded an estimate of 125,112 (CI ± 16,445) responses. Adjusting this figure to take account of the response rate yielded an estimate of 316,070 (SE ± 41,767) breeding pairs. This figure is greatly in excess of the estimate made just 13 years earlier. Possible reasons for this are discussed.

"Comparison with the 1998 census: The results presented here differ strikingly from the results recorded in 1998 (Smith et al. 2001). A change from 101,000 to 316,000 pairs in the estimated population size requires an increase of approximately 9% p.a. For a bird with a low reproductive rate and a long period of deferred
maturity, this is a very high rate. The UK and Irish population of the Northern Gannet Morus bassana has been increasing steadily for many years, but the rates have largely been of the order of 2% p.a., though the population at the Bass Rock has increased by 4.8% p.a. for 35 years (Wanless et al. 2005). During the period when it was spreading rapidly around the UK the Northern Fulmar Fulmarus glacialis achieved rates of increase of some 8% p.a. (Tasker 2004), but this may also have included some immigration.

The only previous attempt to estimate the population size of Manx Shearwaters on Skomer using playback was made in 1995 by Gibbons & Vaughan (1998). They restricted their study to the Neck, a 23 ha area on the east of the island (Figure 1), and obtained a figure of 26,500 pairs (95% CI 21,000–32,000). In comparison, the number of responses on the Neck in 2011 was 22,891 and the estimated population size 56,801 pairs, again very much larger than the earlier estimate.

Possible reasons for this difference include:
i That the population has increased during the 13-year interval. There is some evidence to suggest that there has been an increase. Surveys of 18 0.1 ha plots have been made annually by MSc students from Oxford (Taylor et al. 2011). From 767–1,113 males have responded in the different years, with the numbers showing a significant increase with time. However, at the most, this increase has been only about 2.5% per year, not nearly enough to explain the difference recorded between 1998 and 2011.

ii That the local population has been augmented by large numbers of immigrants. This seems unlikely since, even before the 2011 survey, the Pembrokeshire islands were thought to house 40 % of the UK and Irish
population; an increase through immigration in a smaller population might well occur, but for Skomer this seems unlikely.

iii That there has been a sharp decrease in the age of first breeding. There is no evidence one way or the other, but it seems an unlikely explanation.

iv That the methods used in one (or both) of the surveys were sufficiently flawed to account for the difference, or part of it.

One difficulty with comparing the 1998 estimate with the current one is that the methods used were so different. One possible explanation for the disparity is that the technique used in 1998, of counting all the burrows in mid-winter and visiting a known percentage of these in summer, is faulty. It assumes that the ‘population’ of burrows remains the same throughout the year, whereas there is very heavy digging in spring by all three species - shearwaters, puffins and rabbits. In 2011, the number of burrows counted in the 288 plots was 13,863 and this, correcting for area (as done for responses in Table 2), yields a burrow number of 417,368, almost three times the number counted in winter 1997/98. [Burrows dug in spring are not
normally used for breeding that same year - M. Brooke pers. comm.]

Differences in tape quality or observer behaviour are other possible sources of discrepancy. However, it seems unlikely that these can explain the differences between the two studies since the response rates were similar: 1998 3,218 responses in 11,320 burrows tested (28.4%), 2011 4,475 in 13,863 (32.3%).
While the reasons for the discrepancy between the two censuses needs to be better understood, we suggest that the method used here provides a fast, relatively low-labour way of making estimates of shearwater populations. We believe that the labour involved in establishing the response rate could be greatly reduced by searching for burrows with eggs at the end of May and simply marking and playing the tapes down these without trying to establish who the occupants were. This assumes no significant egg loss prior to the end of May. All that is needed is a response rate from a known number of burrows with eggs. This would potentially enable larger samples to be made and would not only increase the accuracy of the
response rate but also reduce the Confidence Intervals."

Friday 11 January 2013


 James E. Roberts is currently writer in residence on the island of Skomer. He is a poet, based in Wales. His recent work has been published by Agenda, Envoi and the Dark Mountain Project.
The tide is running south and Jack Sound is starting to show its teeth. A mile out Skomer is a humped, finned bulk. I’m looking for familiar shapes; cormorants, fulmars, gannets. But sea and sky are strangely empty this September morning. Even the gulls, usually a constant westward stream, are not present. Two young women are taking photographs of each other on the cliff path in front of me. One leaps while the other clicks away, trying to get a picture of her friend suspended in mid-air. As I pass they both stare at the tiny camera screen, giggling. Their laughter is replaced by a mournful wail. Thirty feet ahead the cliff falls away to a boulder-strewn cove. The edge overhangs the drop and all along the undulating cliff there are the fresh pale wounds of recent rockfalls. I don’t like going up to the edge. These cliffs are the highest I know. But the call is clear, the first of the autumn, echoing faintly in the caves that pierce the headland. I find a perch that feels vaguely secure and sit, my legs hanging over the cliff.
The seal pup is only a few days old. It is pure white, showing up against the grey beach as clear as a gull. It is wriggling and slapping its flippers, its eyes big wet beads, its mouth wide and wailing. The sea is calm in the small, sheltered cove and the water is glass clear. I can see a pale, speckled shape submerged below me. It is not a boulder. With each incoming wave it rolls sideways then rolls back. The pup keeps calling, its cries slowly getting louder. After a few minutes the cow wakes and slides up to the surface. She hauls out to attend to her pup.
In David Thomson’s 1954 book, The People of the Sea, the writer travels along the western fringes of the British Isles recording the seal stories of the oral tradition. The seals are viewed by the fishermen and crofters as liminal creatures, shape-changers, able to shed their skins and take on a range of animal forms. Sometimes they roam as cattle or as horses at night. They also take human shape. In one South Uist tale a young cormorant hunter comes across a pile of seal skins on an island reef. He takes one from the pile and hides it in his boat. Soon a group of handsome people come to the pile. One by one they put on the skins and enter the sea transformed into seals. When they are all gone a woman arrives, even more beautiful than................................ 

Monday 7 January 2013

Guillemot growth on Skomer not just from immigration

Tim Birkhead who has been studying guillemots on Skomer has recently published an interesting paper on the guillemot situation on Skomer. Tim has been involved in studying Guillemots on Skomer for 40 years - and this has been a conclusion of 40 years work. A lot of the statistics for the paper were produce by Jess Meade - who was a Field Assistant on Skomer for two years.

The gist of it is that the expansion of Guillemots on Skomer (Reported here) can be explained by an increase in the population by breeding success and adult survival of Skomer birds alone and that immigration from other colonies (maybe due to poor breeding success) is not necessary to generate the observed growth.

Guillemot population on Skomer Island 1960-2012
The population of common guillemots Uria aalge on Skomer Island, Wales has been monitored since 1963, and in the last 30 yr has increased at an almost constant rate of 5% yr-1. A previous attempt to model the population based on intrinsic demographic parameters estimated over just five years failed to explain the observed population increase, probably  because the estimate of juvenile survival was too low. This raised the possibility that immigration fuelled the population increase. Here we use 30 yr of detailed field observations to re-estimate key population parameters (productivity, adult survival and juvenile survival) in order to model the population. We show that the observed rate of increase can be explained by these intrinsic parameters, and we therefore conclude that immigration is not necessary to generate the observed population growth.

Full paper here.
Meade, J., Hatchwell, B. J., Blanchard, J. L. and Birkhead, T. R. (2013), The population increase of common guillemots Uria aalge on Skomer Island is explained by intrinsic demographic properties. Journal of Avian Biology, 44: 055–061. doi: 10.1111/j.1600-048X.2012.05742.x