From Rare Bird Alert

This year a sedge warbler sang down by Eddie’s Hide (St Ouen’s Bay) every day for several weeks. A lesser whitethroat sang for days at Les Ormes. These birds featured nightly on Jersey Birds and got themselves on to our Farmland Bird Monitoring. Will they have fathered any young?

A new study, by a team from the University of East Anglia (UEA) and BTO, led by Dr Catriona Morrison, illustrates how lone singing males could be an inevitable symptom of species declines. This new research focused on another summer visitor from Africa, the willow warbler, a species that has sadly gone from Jersey as a breeding birds and has experienced a 37% decline across England but a 27% increase in Scotland over two decades, according to the Breeding Bird Survey (BBS). This new study explores the potential causes of skewed sex ratios among small and declining bird populations. The findings indicate that unpaired males are substantially more common in areas with small population sizes, which are primarily found in the south-east region of the UK. These imbalances in sex ratio may be down to female choice, as female willow warblers may be selecting busier breeding locations, where habitat quality may be better and males are more abundant. This leaves male migrants unpaired in poorer sites; many – like our local sedge warbler – could be on their own for the whole season.

Speaking about the aims of the new study, Prof Jenny Gill, from UEA’s School of Biological Sciences, said: “Many migratory bird populations are declining and very small, isolated, local populations are becoming more common. If females prefer places where males are more abundant, small populations are likely to decline even faster. We wanted to find out whether this is happening.” The UEA/BTO research team used BTO ringing data from Constant Effort Sites to explore the extent, causes and consequences of variation in sex ratios in breeding populations of willow warblers across the UK. Around 8,000 birds were surveyed from 34 sites over 18 years.

Skewed sex ratios

Male-biased sex ratios occur in many bird species but are particularly common in those with small or declining populations. However, the reasons behind this and the implications for the success of local populations have rarely been investigated at large scales. Perhaps female survival is lower in areas where populations are in decline or there may be differences in the way that males and females decide where to breed? Although numbers are declining, willow warblers are sufficiently widespread and numerous to enable investigation of these issues.

New willow warbler research

Reflecting, Dr Morrison, said: “In 1994, the male-female ratio was pretty much 50:50 for willow warblers across the UK but, over time, males started to outnumber females. By 2012, males comprised around 60 per cent of the population, with sites with smaller numbers of birds having a greater proportion of males. So, for example, in sites in the north-west of the UK, where willow warblers are very abundant, the male-female ratio was still close to 50:50, but higher proportions of males were common at sites in the south-east, where there are many fewer willow warblers. Unfortunately, as time goes by, we are finding there are more male-dominated sites, probably because ongoing habitat fragmentation means that small populations are becoming more common. As expected, we found proportionately fewer juveniles in male-biased sites.

Males are highly site-faithful and females may well be preferentially joining sites with larger populations – perhaps because they are attracted to the males, or because there is more suitable habitat. Having skewed sex ratios is problematic because it means a proportion of individuals will not be able to find a mate and breed. This could potentially drive faster declines in small populations,” she added.

Male-biased sex ratios could arise from greater female mortality in small populations, for example if poorer resources in these sites compound the greater costs of breeding for females. However, the authors found little evidence that this was the case; the increasingly frequent occurrence of male bias in willow warblers is not matched by any trends in male or female survival rates. This strongly suggests that females are more likely to recruit into larger populations and thus that conservation efforts should focus on maintaining and enhancing sites capable of supporting large populations that are likely to have more equal sex ratios.

What does this mean for our bird monitoring programmes?

The willow warbler is one of many migratory species in decline across Europe and declining sharply in the south-east region of the UK it no longer breeds in the Channel Islands where it was once a common bird. If small, local populations are increasingly frequent in these species, as a result of habitat fragmentation, male-bias may be becoming increasingly common. Given that singing males are the primary records used in surveys such as the Breeding Bird Survey and as unpaired males, unlike paired males, often sing throughout the breeding season, it is more likely that they will be recorded on surveys. These lone, singing willow warblers, turtle doves and nightingales may be artificially boosting figures and inadvertently under-playing the plight of their species.

The full paper Causes and consequences of spatial variation in sex ratios in a declining bird species can be downloaded here

From Alderney Wildlife Trust

Alderney Wildlife Trust (AWT) has once again teamed up with the British Trust for Ornithology (BTO) and the University of Liverpool to provide the public with a unique glimpse of life in the British Isles’ most southerly gannet colony.

Saturday 25th June saw the launch of the second year of the Track a Gannet (T.A.G.) project – tracking the movements of Alderney’s northern gannets as they leave their colony to forage throughout the English Channel and beyond. The 12 tags deployed this year are on birds from the 5,600-strong colony of Ortac and will use the 3G mobile network to transmit data on the gannets’ movements as they forage for fish. See report on the project in 2015 here.

The map shows the movements of the 2015 tagged birds – many of the areas the birds pass through and directly feed in are potential sites for renewable development in the Channel. While the proposed energy developments for the Channel could go some way to providing a source of clean energy and reducing CO² emissions for the UK, it is vital that we understand both the positive and negative impacts these developments might have. The data gathered during the T.A.G. project will go some way to providing essential data on gannet movements and how it changes from year to year, helping the collaborative team best advise on the impact developments will have on biodiversity and paving the way for more in-depth studies on the ecology and health of the waters of the Channel.

Northern gannets, the largest breeding seabird in the North Atlantic, are currently amber listed in the UK. Fortunately in Alderney the number of birds is increasing annually – especially important as the two colonies (approximately 8, 800 pairs) here make up over 2% of the world population. The longest single foraging trip from 2015 from a single bird was over 800km – a long way to go for a fish supper! This long-distance trip passed very close to several wind farm development areas, showing how far-reaching the effects of marine developments could be.

T.A.G. allows the public to follow the movements of this charismatic species in near real- time as the tags, which are attached to the gannets’ tail feathers, send updates on movements for up to six weeks every time they come into contact with a 3G mobile network. The flight paths of Alderney’s gannets can be found here. For meaningful, usable data we aim to run the T.A.G. project for at least three years – the project has already contributed to one PhD and one MSc study and we hope this will continue in future.

T.A.G. is coordinated by the Alderney Wildlife Trust in collaboration with the University of Liverpool, the Alderney Commission for Renewable Energy (ACRE), the BTO and local businesses and members of the general public who have sponsored and named birds themselves including Action for Wildlife Jersey. We are also delighted to say that T.A.G. is the overall winner of the Channel Islands Insurance Corporation’s Conservation Awards. Not only has the prize money enabled us to deploy more tags but it also helps us raise the profile of the conservation efforts in Alderney within the Bailiwick of Guernsey and beyond.

Roland Gauvain, AWT Manager, says “T.A.G. provides a vitally important long-term baseline for a key foraging seabird in the English Channel. Run entirely outside of the UK and EU funding process, it is dependent on the support of individuals and visitors here on our little Channel Island and the BTO and Liverpool University who have the foresight to support such a long-ranging project. Our thanks go out to our partners and we wait with baited breath to see what the birds are up to this year”!

Dr Jonathan A Green, Senior Lecturer in Marine Biology at the University of Liverpool added “We are proud to be able to assist AWT with this innovative project that combines public support with cutting-edge science. T.A.G. provides an insight into the lives of this iconic species and helps us to understand their place in a rapidly changing marine environment”.

How to see Alderney’s gannets – For anyone wanting to see both the gannets and the tags first hand they can visit the new website here to see the live map, updating the movements of the gannets.

The AWT also works closely with Visit Alderney to enable visitors to Alderney to get out and see Alderney’s seabirds by boat, especially the gannets, but also the largest breeding puffin population in the English Channel proper.

From Audubon Science

It takes a special kind of fish diet to feed a growing Atlantic puffin. A chick can eat more than 2,000 fish before leaving the nest, and they all need to have the perfect size, shape, and fat content. This report from the USA range of the Atlantic puffin is very relevant to this species on our side of the Atlantic.

Each summer off the coast of Maine (USA), scientists with Audubon’s Project Puffin document the finicky diets of pufflings, tracking the species, quantity, and size of the fish that the parents deliver to their young. They also weigh and measure the fuzzy nestlings and track their hatching, fledging, and survival rates. This type of long-term data is scarce for this species, says Steve Kress, director of Project Puffin—yet it’s integral for connecting puffin survival rates to the effects of climate change and commercial fisheries.

Now, a new study by Kress and co-authors, published last week in FACETS, forges that link by showing that pufflings’ diets are changing fast. Using data that dates back to 1993, the experts calculated that post-fledging survival rates have declined by an average of 2.5 percent per year, and that the chicks’ body condition has declined as well. The reason, Kress says, is a less-than-ideal menu, caused by climate change and pressures from fisheries.

How are the chicks’ diets changing?

Puffins are particularly sensitive to changes in local fish populations because they return to the same island burrows year after year; most end up raising their own chicks at the same sites where they hatched. Parents generally gather fish and crustaceans for their pufflings within a 12-mile radius of the nest. Little is known about what the adults eat, since they feed at sea, so the young provide a window into the relationship between fish and puffins. “I think of them as little fishing fleets going out every day . . . to see what they can catch, and then they come back with the catch of the day,” Kress says.

The most frequent catch recorded between 2005 and 2014 was white hake, followed by Atlantic herring, but fewer of these fish were seen over time. On the other hand, the proportion of butterfish, haddock, and redfish increased in the birds’ diets—none of these species were present during the earlier years of the study.

This changing menu is important because puffin chicks are very particular about their meals. They can only fit smaller, narrower fish – like white hake (a species not seen in European waters) – into their beaks and often have trouble swallowing larger, oval-shaped species like butterfish (another species not seen in Europe where snake pipefish represent a similar problem). And since puffin parents don’t tear up the fish for their young (unlike some other birds), the babies have to swallow their food whole. In 2012, Audubon’s Puffin Cam documented Petey the chick starving to death after his parents brought him butterfish that were impossible for him to eat.

What’s causing these shifts?

It seems that climate change is disrupting the pufflings’ diets—and the entire marine food web—by heating up the ocean and reducing the abundance of plankton that fish need to eat. White hake and Atlantic herring thrive in colder waters, as there tends to be more plankton there. That means schools are moving northward and deeper, where puffin parents may not be able to reach them. Plankton and fish populations are also affected by climate-driven increases in precipitation and ice melt, which alter water clarity and salinity.

Additionally, on the two islands where the scientists studied the chicks, hatching success and fledging rates declined significantly from 2010 to 2013, with the two worst years corresponding to unusually warm ocean temperatures. They rebounded in 2014 following a winter with colder water. This type of “ocean heat wave” is expected to become more frequent due to climate change, so the low hatching and fledging rates could be a preview of how puffins respond to warmer seas.

Humans may also be playing a direct role in the chicks’ hardships, specifically through mismanagement of commercial fisheries. It’s a double bind for the young, inexperienced birds, Kress says. “The puffin [fledgling] is headed off into a warmer sea affected by climate, which is less productive, and it’s also headed into a sea that’s being heavily fished by commercial fisheries.” For example, most of Maine’s herring—a puffling favourite—is snapped up for lobster bait. It’s possible that the new, more heat-tolerant species could meet the chicks’ dietary needs, but it’s still up in the air whether the timing of their migrations will match the puffins’ breeding season.

Kress emphasizes that there is hope for protecting Atlantic puffins in the future. But people need to look at the bigger picture. Tightening up restrictions on commercial fisheries, limiting carbon emissions, and protecting the birds’ wintering grounds will be essential in the years ahead. “You can protect the islands, as we are and as we must,” Kress says, “but if the fish are not protected and the habitat is not protected, then the work on the islands is not sufficient.”

The full report Recent changes in the diet and survival of Atlantic puffin chicks in the face of climate change and commercial fishing in midcoast Maine, USA can be downloaded here

Results are now available from the Birds On The Edge Island-wide Farmland Bird Monitoring scheme, managed by the Durrell Wildlife Conservation Trust through collaboration between Durrell, the Société Jersiaise, the National Trust for Jersey and the States of Jersey Department of the Environment and carried out at five sites between 2005 and 2015 that show that Jersey’s farmland bird populations are poorer than previously thought.

Five sites (at Crabbé, Les Landes, Les Blanche Banques sand dunes, Noirmont and Les Creux) were chosen in part through their connection with the five landbirds detailed in Jersey’s biodiversity action plans published in 2006: skylark, Dartford warbler, stonechat, yellowhammer and cirl bunting. Each of the transects have been walked at two-week intervals throughout the year and types and numbers of birds at different distance bands have been recorded. The dedicated team of volunteers walked more than 1,920 miles over 10 years in order to see what is happening to our birds.

Bird monitoring provides one of the most robust and globally recognised methods for measuring changes in the state of biodiversity and the broader environment. Currently the UK Farmland Bird Indicator is one of the UK Government’s 15 sustainable development indicators.

Over the ten-year period the information collated can be used to identify trends in populations and evidence suggests that we are dealing with very much a ‘mixed bag’.

A total of 124 bird species were recorded at the five sites during the survey, April 2005 to April 2015. Some of these species were recorded very infrequently or even only once and of all those recorded, 72 species were seen in sufficient numbers to analyse trends.

Linnet: FBS counts 2005-2015

Total numbers of birds recorded on Jersey’s north coast 1985-2014

Sixteen of them showed marked decreases across the five sites while a further nine have increased. The remaining species’ populations appear stable with three showing signs of a possible long-term increase and five showing signs of a possible long-term decrease. Results coincide with a 30-year survey of birds along Jersey’s north coast published by the Société Jersiaise which shows that overall bird numbers recorded here halved between 1985 and 2014².

Dr Glyn Young of Durrell, who managed the project, said “the results of these two studies show the importance of long-term monitoring projects like this one and is grateful to everyone who gave so much of their free time to help understand what is happening to our Island’s bird populations”.

Mick Dryden, Chairman of the Société Jersiaise Bird Section said “The Section has collected bird records for more than 50 years from right across Jersey. This study has clearly shown the value of intensive, systematic study from a group of keen volunteers”.

Turtle dove: FBS counts 2005-2015

In Jersey there are many species of conservation concern, but, as this study shows, it is birds associated with farmland such as the lapwing, turtle dove, skylark, yellowhammer, stonechat, linnet and reed bunting, that are faring the worst in terms of declining rates. This follows a present trend across the UK and Europe. It has been determined that the main causes of these declines are an unusually high mortality during winter, a direct consequence of the modernization of farming techniques, abandonment of marginal land and a changing climate. In traditional agriculture, there would be sources of winter food in the form of spilt cereals, fields left in stubble and fallow grounds. In Jersey it is not known what changes in farming are having an impact on local birds, but it is believed that a combination of intensification, modern technologies and abandonment of marginal land which then reverts to bracken have contributed to the changes in the food availability and subsequent bird declines.

Skylark: FBS counts 2005-2015

Birds are great indicators for overall environmental health and birds in Jersey are in decline, the island’s broader environment is a lot poorer than people assume. Jersey needs a healthy and diverse environment to prosper, so help the birds and help Jersey.

What is being done to benefit these target species which have been identified to be declining in numbers? The Birds On The Edge partnership is a joint initiative between The National Trust for Jersey, Durrell Wildlife Conservation Trust and the States of Jersey Department of the Environment, which aims to restore habitats and stop the decline of these bird species.

As an integral part of the Birds On The Edge project and in collaboration with local farmers, a total of 49 fields (with a combined area of 30.35ha or 168.6vg) were planted with winter bird crops in 2015 at 12 different sites. Three varieties of winter bird crops were planted and some barley and mustard. This initiative aims to help our birds get through the winter when food would otherwise be very scarce and be in good condition to breed in spring.

Each of the sites surveyed and the core populations of the declining birds lie within the Jersey Coastal National Park, further emphasising the importance of this initiative to Island biodiversity.

Jonny Parkes, Lands Manager of The National Trust for Jersey says “This survey clearly demonstrates that we all need to “up our game” if we are going to prevent the further loss of some of our key farmland and coastal birds. The loss of the skylark from the dunes at St Ouen would be tragic loss and we need to acknowledge that securing the future of such species will require on occasion robust measures including restricted public access, pest control and increased government investment in agri-environment schemes. The Birds On The Edge Project demonstrates what can be achieved through collaboration and we hope we can further build upon its early success to prevent further population declines”

¹ Download the full survey report here

² Read details of the north coast bird survey here