Gannet – 2013 research

Morus bassanus – HUGAN – Breeding resident.

Article from Science Daily, March 14, 2013

The European Parliament recently voted to scrap the controversial discards policy, which has seen fishermen throwing thousands of edible fish and fish waste back into the sea because they have exceeded their quotas.

Scientists at Plymouth University believe this could have a negative impact on some seabirds, which have become used to following the fishing vessels and are increasingly reliant on their discards.

But they say others could return to using foraging as their sole source of food, as long as there are sufficient numbers of fish to meet their needs.

Dr Stephen Votier, Associate Professor in Marine Ecology at Plymouth University, led the study. He said: “Policy changes can have unforeseen consequences, and the recent decision on the EU discards policy will pose challenges for a number of species. Many seabirds have come to rely to some extent on fishing vessels for food and globally, commercial capture fisheries generate huge quantities of discards. However, we believe there is a level of resilience among seabirds which means they will be able to overcome these challenges.” The study focused on populations of northern gannets on Grassholm Island, in Wales, with tiny cameras and GPS trackers being attached to birds to monitor their foraging habits.

The cameras captured more than 20,000 images, allowing scientists for the first time to analyse where the birds had flown to source food, precisely what they had fed on, and other details such as their sex and reproductive status.

The findings showed 42% of birds regularly targeted fishing vessels, as well as searching for naturally occurring prey, while 81% of male gannets used fishing vessels to source food and 30% of female birds did so.

Dr Votier added: “We have used cutting-edge technology to reveal the private lives of seabirds at sea — in this instance how they interact with fisheries — and the findings suggest scavenging is more common in this species than previously thought. This suggests a discard ban may have a significant impact on gannet behaviour, particularly so for males, but a continued reliance on ‘natural’ foraging shows the ability to switch away from discards, but only if there is sufficient forage fish to meet their needs in the absence of a discard subsidy.” The research study, which also involved scientists from the Plymouth Marine Laboratory and the Centre d’Etudes Biologiques de Chize in France, was conducted under licence from the Countryside Council for Wales and the British Trust for Ornithology.

It received funding from the National Environment Research Council, and the full findings are published in the latest issue of the PLOS ONE scientific journal.

Stephen C. Votier, Anthony Bicknell, Samantha L. Cox, Kylie L. Scales, Samantha C. Patrick. A Bird’s Eye View of Discard Reforms: Bird-Borne Cameras Reveal Seabird/Fishery InteractionsPLoS ONE, 2013; 8 (3): e57376 DOI: 10.1371/journal.pone.0057376

Update on Tuesday, November 12, 2013 at 8:27AM by Pembrokeshire Avifauna committee

More on this story at BBC Nature including a video clip – a gannet’s eye view of the world.

More about the Gannet in Pembrokeshire

Kestrel – 2012 research

Falco tinnunculus – CUDYLL COCH – Breeding resident

Kestrel numbers within the county have declined and are now considered to be at their lowest level since 1894. The reasons for the decline are discussed in detail. Much of the decline is attributable to loss of suitable breeding habitat due to changes in farming practices, but there are also other contributing factors. Productivity seems sufficient to maintain a viable breeding population, but many successful breeding sites become unoccupied in subsequent years. This indicates that either adult survival between breeding seasons is too low, or insufficient recruitment is taking place due to low survival of first winter birds following independence, or perhaps both.

A likely cause of the low survival of first winters is again change in farming practices reducing the foraging quality of the arable landscape but this assumes that Pembrokeshire kestrels disperse to lowland arable areas to over winter in line with the national trend (Shrubb 1993), an assumption for which there are no data to help validate. Predation cannot be ruled out as a cause of poor over-winter or post-fledging survival, but during the breeding season it appears to be insignificant. Competition for nest sites may occur inland and the provision of artificial sites in some areas may help, but it is concluded that nest site competition in not a significant factor that is driving the population decline, and until other factors are understood and mitigated for, then the kestrel population will not increase significantly in response to provision of artificial nest sites.

Paddy Jenks & Tansy Knight

More about the Kestrel in Pembrokeshire

Manx Shearwater – 2012

Puffinus puffinus – ADERYN-DRYCIN MANAW – Numerous breeding summer visitor. Recorded in all months

Hormones dictate when youngsters fly the nest

Published Thursday 5 July 2012

Image credit: David Boyle

Seabirds feed their young less as they reach an age to fly the nest, but it’s hormones that actually control when the chicks leave home, according to new research from the University of Leeds.

The study – published in Behavioural Ecology – aimed to pinpoint the main trigger which causes chicks to leave the nest and embark on an independent life, a process known as fledging.

While studying a colony of Manx Shearwaters (Puffinus puffinus), on the island of Skomer, researchers from the University’s Faculty of Biological Sciences noticed that parent birds seemed to become increasingly insensitive to their chicks’ demands for food as they grew close to fledging. At the same time the chicks showed a marked increase in levels of the hormone corticosterone. However, the team needed to know whether this increase was independent of, or caused by, the reduction in feeding.

They decided to trick the parent birds, by swapping chicks of different ages between nests – which the birds make in burrows in the ground – to see how this affected both parental care and the time chicks took to fledge.

“Manx Shearwaters don’t recognise their own offspring, but will simply go back to the same nest after they’ve gathered food. They have one chick, which makes the interactions between parent and offspring easier to study,” explains lead researcher, Dr Keith Hamer. “We swapped chicks which were between 10 days and two weeks apart in age, to see what impact it would have. We wanted to find out whether parents and chicks were responding to each other’s behaviour, or whether each was acting independently.”

The team discovered that adults reduced their food provisioning after about 60 days of raising a chick, regardless of the chick’s stage of development. Although females more than males will adjust their feeding levels to how much their chicks beg for food, after around 60 days both parents start to ignore their pleas. This held true whether parents were feeding their own chicks, or foster-chicks of different ages.

The surge in corticosterone took place over the final few weeks before chicks fledged at about 70 days of age. This held true even when chicks had been fostered by parents at a different stage of the feeding cycle, so was clearly independent of the parent’s behaviour and any reduction in food. 

“Our findings show that young Manx Shearwaters leave home of their own accord when their corticosterone levels have reached a peak rather than as a result of changes in parental behaviour,” says Dr Hamer. “Both parents and chicks need large energy reserves for their arduous migration across the Atlantic to South and Central America, and parents seem to reduce how much they feed their young simply to protect themselves.”

“Unlike some other bird species, which let their offspring dictate the level of care, seabirds appear to weigh up the cost of a chick fledging underweight against the greater cost of losing the chance to breed again,” he adds. “Manx Shearwaters have a breeding life of around forty years, so parents pay a high cost if they end the season too weak to complete their own migration.”

Press release by Univeristy of Leeds

Keith Hamer et alParent–offspring conflict during the transition to independence in a pelagic seabird.Behavioural Ecology, 2012 DOI: 10.1093/beheco/ars079

More about the Manx Shearwater in Pembrokeshire

Guillemot – 2012 Tim Birkhead

Uria aalga – GWYLOG – Breeding resident, passage migrant and winter visitor

Scientist spends 40 years studying island’s seabirds

A bird expert at the University of Sheffield has spent 40 years studying seabirds on an island off the UK in one of the longest running investigations of its kind.

Professor Tim Birkhead

See Video here

Professor Tim Birkhead, of the University’s Department of Animal and Plant Sciences, first visited Skomer Island – situated off the cost of west Wales – in 1972 and since then he has returned every summer, gaining invaluable information about guillemots.

He will visit the island again on June 21 2012 for 10 days, marking his 40th breeding season studying the guillemots, conducting an annual census and ringing the birds to see how old they are when they start to breed and how long they live.

Professor Birkhead said: “It has been an invaluable investigation, for example it is clear that climate change has had a huge effect on the guillemots as they now breed two weeks earlier than they did in the 1970s. We also know a huge amount more about guillemot biology than we did 40 years ago, and we can use changes in guillemot numbers to tell us what is happening in the seas surrounding the island.

“Long term studies like this are few and far between but remain vital for understanding changes taking place in the environment. It’s been a constant challenge both to secure funding and to carry out the work itself as the birds breed on the sea battered cliffs of a remote island.”

Home to about half a million seabirds, including the guillemots, razorbills and puffins, uninhabited Skomer Island is a natural nature reserve, specially protected and a site of scientific importance.

Technological advances throughout the four decades have enabled Professor Birkhead to gain even more information about the birds.

Guillemots on the islandGuillemots on the island

He added: “Using new tracking technologies, like GPS and geolocators, we now have a very complete picture of where guillemots go to forage. During the breeding season they forage within about 60 km of Skomer in the south Irish Sea, but in winter they travel huge distances moving between the Bay of Biscay and the far north of Scotland.

“We also know from guillemots research elsewhere around the UK coast that Skomer is extremely fortunate to be enjoying an increasing population. At other colonies the lack of fish has caused massive breeding failures, reduced survival and decreasing populations.”

During the early stages of the pioneering study, Professor Birkhead came up with innovative ways to overcome the many technical challenges he faced. In 1972 no one knew how to conduct a census of guillemots as it had never been tried before.

The second task was to determine how many chicks were produced each year and whether it was enough.

In 1972 when Professor Birkhead began his studies the guillemot population breeding on Skomer was just 2,000 individuals, yet pictures of the island thirty years earlier showed that there were around 100,000 guillemots then. In 2011 numbers were up to 20,000 individuals.

By marking birds individually with colour rings Professor Birkhead was able to measure their breeding success, see how old they are when they first start to breed and see how long the birds live.

Adult guillemots have an annual survival rate of 95 per cent and equivalent of an average life span of 25 years. On average about 80 per cent of guillemot pairs successfully rear a chick to fledging, and of these around half survive to breeding age, which is seven years old. This high survival of immature birds more than off-sets the natural mortality of the adult birds, so the population has increased.

Sheffield University News Release – 26 June 2012

More about the Guillemot in Pembrokeshire

Whinchat – 2012 research

Saxicola rubetra – CREC YR EITHIN – Breeding summer visitor and passage migrant. Not recorded from December to February

The Whinchat Saxicola rubetra is a migrant breeding species favouring open country such as heathland, moorland, bogs, marshes and light scrub. The latest atlas of breeding birds in Pembrokeshire 2003-07 (Rees et al 2009) found that their distribution had been reduced by 70% in comparison to the 1984-1988 atlas. And this range contraction is accompanied by a 50% population decline. The species is currently amber listed and a local priority species.The aims of this survey are to record in detail the current breeding status and distribution of whinchats in Pembrokeshire, and to relate this distribution to habitat. This will lead to a greater understanding of habitat requirements and enable practical land management advice to aid their conservation within the PCNP.

A set of sites where whinchats have bred in recent years within the PCNP were surveyed; St Davids Head, Dowrog, Fagwr Goch, Carn Ingli, Fronlas and Brynberian Moor. Several additional sites were visited on an ad hoc basis. These were; Pantmaenog, North Preseli east of Brynberian, Mynydd Crwn, Afon Wern.

An initial visit was made to each of these sites between 20th May and 10th June and follow up visits were made between 19th June and 5th July. 

No breeding Whinchats were found at either of the St Davids sites and neither did they appear at the two farms south of the Preseli ridge; Fronlas or Fagwr Goch.

A total of 29 pairs were found spread across all the remaining sites with 15 of these at Brynberian Moor.

14 nests were located and based on 11 successful nests for which brood size was known (across all sites) productivity was 4.5 young per nest.

All breeding pairs occupied a mosaic of bracken, low bushes of various species and a wet area such as a gully or flush.

The reasons for the decline in the local Whinchat population were considered. Productivity data are represented by a small sample but based on this surveys results it appears to be near the national average for first broods. There was unoccupied but apparently suitable breeding habitat, suggesting that recruitment is low, possibly caused by factors away from their breeding sites. There was no evidence that Stonechats displaced breeding Whinchats and predation was considered to be an insignificant factor. 

Practical habitat management to favour breeding Whinchats is discussed. The current grazing regime at Brynberian Moor is already well suited to maintaining good whinchat habitat, so it is not necessary to change current practise. Targeted burning of bracken near gullies and mature gorse is likely to be detrimental to the population. Creating small isolated pockets of Whinchat habitat at new sites will probably be ineffective as long as there remains unoccupied suitable habitat.

Whinchats are a very easy species to census, with a single visit made to their breeding sites any time between mid-May and the end of June producing identical and reliable results, and by ringing chicks during June and July a very valuable data set can be established over a few years.  

Read the full report here

Paddy Jenks, Tansy Knight & Jane Hodges

More about the Whinchat in Pembrokeshire

Balearic Shearwater – 2012 geolocator study

Puffinus mauretanicusAderyn-Drycin Môr y Canoldirannual visitor.

Using combined miniature archival light and salt-water immersion loggers, we characterise the year-round individual at-sea movements of Europe’s only critically endangered seabird, the Balearic shearwater Puffinus mauretanicus, for the first time. Focusing on the non-breeding period, we show that all of the 26 breeding birds tracked from their breeding site on Mallorca in the Mediterranean Sea successfully made a 2–4 month migration into the Atlantic Ocean, where they utilised well-defined core areas off Portuguese and French coasts.

As well as identifying high-risk areas in the Atlantic, our results confirm that breeding birds spend most of the year concentrated around productive waters of the Iberian shelf in the western Mediterranean. Migration phenology appeared largely unrelated to the subsequent (distinctly synchronous) breeding attempt, suggesting that any carry-over effects were compensated for during a long pre-laying period spent over winter in the Mediterranean.

Using the light and salt-water immersion data alone we were also able to characterise the pattern of pre-laying visits to the colony in considerable detail, demonstrating that breeding pairs appear to coordinate their over-day visits using a high frequency of night-time visits throughout the winter.

Our study shows that geolocation technology is a valuable tool for assessing the spatial distribution of risks to this critically endangered species, and also provides a low-impact method for remotely observing the detailed behaviour of seabird species that may be sensitive to disturbance from traditional study methods.

Full article here

Citation: Guilford T, Wynn R, McMinn M, Rodríguez A, Fayet A, et al. (2012) Geolocators Reveal Migration and Pre-Breeding Behaviour of the Critically Endangered Balearic Shearwater Puffinus mauretanicus. PLoS ONE 7(3): e33753. doi:10.1371/journal.pone.0033753

More about the Balearic Shearwater in Pembrokeshire

Puffin – 2011 research

Fratercula arctica – PAL – Breeding summer visitor

A Dispersive Migration in the Atlantic Puffin and Its Implications for Migratory Navigation

Individual Atlantic puffins ‘scout out’ their own migration routes rather than relying on genetic ‘programming’ or learning routes from a parent, a new study suggests.

The evidence comes from research by a team from Oxford University and Microsoft Research Cambridge which used BAS geolocater tags to track the migration movements of 18 birds: with 8 of these birds being tracked for two consecutive years.

The study found that the birds followed a wide range of different migration routes (suggesting their movements were not genetically predetermined) but that they were not merely random as the same bird followed a similar route each year. Because young puffins leave colonies at night, alone, long before their parents, the idea that they might learn a route directly from others also seems extremely unlikely.

‘We think it’s likely that, before they start breeding, young puffins explore the resources the ocean has to offer and come up with their own individual, often radically different, migration routes,’ said Professor Tim Guilford of Oxford University’s Department of Zoology, who co-led the study. ‘This tendency to explore may enable them to develop a route which exploits all the best food sources in a particular area wherever these might happen to be.’

The team believe this kind of ‘scouting’ for good migration routes could also be used by many other species of birds, especially seabirds — which can choose to stop and feed anywhere on the ocean during their migration.

The full article can be found here

Guilford T, Freeman R, Boyle D, Dean B, Kirk H, et al. (2011) A Dispersive Migration in the Atlantic Puffin and Its Implications for Migratory Navigation. PLoS ONE 6(7): e21336. doi:10.1371/journal.pone.0021336

More about the Puffin in Pembrokeshire

Manx Shearwater – 2008

Puffinus puffinus – ADERYN-DRYCIN MANAW – Numerous breeding summer visitor. Recorded in all months

Migration and stopover in a small pelagic seabird, the Manx shearwater Puffinus puffinus: insights from machine learning.


The migratory movements of seabirds (especially smaller species) remain poorly understood, despite their role as harvesters of marine ecosystems on a global scale and their potential as indicators of ocean health. Here we report a successful attempt, using miniature archival light loggers (geolocators), to elucidate the migratory behaviour of the Manx shearwater Puffinus puffinus, a small (400 g) Northern Hemisphere breeding procellariform that undertakes a trans-equatorial, trans-Atlantic migration. We provide details of over-wintering areas, of previously unobserved marine stopover behaviour, and the long-distance movements of females during their pre-laying exodus. Using salt-water immersion data from a subset of loggers, we introduce a method of behaviour classification based on Bayesian machine learning techniques. We used both supervised and unsupervised machine learning to classify each bird’s daily activity based on simple properties of the immersion data. We show that robust activity states emerge, characteristic of summer feeding, winter feeding and active migration. These can be used to classify probable behaviour throughout the annual cycle, highlighting the likely functional significance of stopovers as refuelling stages.

Full article here

Citation: Guilford, T., Meade, J., Willis, J., Phillips, R. A., Boyle, D., Roberts, S., Collett, M.,Freeman, R. and Perrins, C. M. (2009). Migration and stopover in a small pelagic seabird, the Manx shearwater Puffinus puffinus: insights from machine learning. Proc. R. Soc. Lond. B 276, 1215-1223

More about the Manx Shearwater in Pembrokeshire

Guillemot – 2005

Uria aalga – GWYLOG – Breeding resident, passage migrant and winter visitor

Oil spills and climate change double the mortality rate of British seabirds

New research from the University of Sheffield has shown that major oil spills and a changing climate have had a far greater impact on populations of British sea birds than was previously thought.

A team led by Professor Tim Birkhead from the Department of Animal and Plant Sciences at the University of Sheffield, has shown for the first time that major oil spills double the mortality rate of adult guillemots in Britain, even though the pollution occurs hundred of miles from the birds’ breeding grounds. The research, which is to be published in the November issue of Ecology Letters also shows a direct link between a warmer climate in the North Atlantic and a higher mortality rate among British guillemots.

Professor Birkhead’s long-term guillemot study has been carried out on Skomer Island, Wales, since 1972. The length of the ongoing study has allowed the research team to study the effects of a number of serious winter oil spills on the guillemot population. Their findings show that highly publicised oil spills in southern Europe, such as the Prestige oil tanker disaster off the coast of Galicia, Spain, in November 2002, have far-reaching consequences on seabirds breeding far from the scene of the initial pollution.

The study has also found that consistently high values of the North Atlantic Oscillation (NAO) index (an annual measure of a large scale climatic phenomenon affecting winds, temperature and rainfall) for the past 30 years, has had a negative effect on the guillemot population of Skomer Island.

Professor Tim Birkhead of the University of Sheffield said: “Prior to our investigation of the guillemot population of Skomer Island, the impact of oil pollution on seabird mortality rates at a particular colony was difficult to quantify as oil spills usually occur in wintering areas where birds from many different colonies may be distributed over a wide area. However, our long-term monitoring of individually marked birds on Skomer Island has enabled us to see a direct correlation between major oil pollution events and a twofold increase in winter mortality rates of common guillemots.

“Our research has also shown that the NAO index has had a significant effect on the guillemot population. The consistently high values of this climatic phenomenon for the past 30 years may be due to human-induced global climate change. If this is the case, it would mean that seabirds are vulnerable to human activities on two counts: oil pollution from tanker spills and changes to the ecosystem as measured by the NAO index and caused by global climate change from man’s burning of fossil fuels.”

News release from Sheffield University – 25 October 2005

More about the Guillemot in Pembrokeshire

Red-throated Diver – 1996 oil spill

Gavia stellata – TROCHYDD GYDDFGOCH – Winter visitor and passage migrant. Recorded in every month except June

The tanker “Sea Empress” grounded outside the Heads approaching the Milford Haven waterway on the 15th February 1996. Approximately 72,000 tonnes of crude oil and 360 tonnes of heavy fuel oil spilled into the sea between the 15th and 21st of February. Further fuel oil was spilled when the ship was moved to Belfast.

The waterway within Milford Haven was heavily coated and much of the oil was carried south and east to affect the south Pembrokeshire coast and Carmarthen Bay. The offshore islands were not heavily contaminated nor was St Bride’s Bay, with no oil reported north of St David’s Head.

123 Red–throated Divers were known to be in Pembrokeshire waters in January and February prior to the oil spill, the largest concentrations being 10 at Fishguard Harbour, 17 at Frainslake, 20 off Amroth and 75 in Goultrop Roads. Of these, only the Amroth birds were in the badly oiled area, as were five at Freshwater East.

Ten oiled birds were collected from the south coast of Pembrokeshire but a further 49 from the nearby affected coasts of Carmarthenshire and West Glamorgan (SEEC, 1996). Those at Goultrop Roads disappeared and may well have been involved in the movement of 96 passing Strumble Head, going into Cardigan Bay, on the 25th February.

Graham Rees. Pembrokeshire County Bird Recorder 1981-2007


More about the Red-throated Diver in Pembrokeshire