Whinchat - 2012 research

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 David’s 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 David’s 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 

Manx Shearwater - 2012 - research

Hormones dictate when youngsters fly the nest

Published Thursday 5 July 2012

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.”

Image credit: David Boyle

Press release by Univeristy of Leeds

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

Image credit: David Boyle

Seabird research - 2012 Skomer

Sheffield University News Release - 26 June 2012

Scientist spends 40 years studying island’s seabirds

See Video here

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, 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.

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.
 

Guillemots on the island

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.

Professor Tim Birkhead

Seabird mortality & oil spills - 2005 research

News release from Sheffield University - 25 October 2005

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."

Gannet - 2013 research

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 Interactions. PLoS 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.

Puffin - 2011 reserach - migration strategy

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