Following publication of the landmark book Les Minquiers – A Natural History Birds On The Edge asked one of the authors, Paul Chambers, to discuss the book and these remarkable but poorly known islands.

Situated just 12 miles south of St Helier, the tangle of rocks, reefs and sandbanks that form Les Minquiers is a world entirely removed from the bustle and traffic of Jersey life.

At 300 km² the Minquiers’ plateau is larger than most British cities and yet at high tide only 0.002 km² remains above the sea. Six hours later (and drop in sea level of up to 13 metres) and the area of exposed seashore expands by some 10,000 per cent to 20 km². The reef holds around 20,000 individual rocks the oldest of which are at least 640 million years old. The one vegetated island, Maîtresse Île, has a rich prehistoric archaeology which suggests it has been regularly used by humans over the past 4,500 years.

This wonder of the natural world is sat on Jersey’s doorstep and yet until recently very little was known about the history or natural history of Les Minquiers. ‘There is perhaps no area of comparable extent in the British Isles about which so little is known,’ wrote the celebrated geologist Dr Arthur Mourant in 1977. This remained true until 2012 when a small team from Jersey’s Société Jersiaise set out to document the reef’s marine and terrestrial biology.

Following the recent publication of the team’s landmark book on the history and natural history of Les Minquiers (see book here) we are pleased to present an overview of the current ecological health of Les Minquiers. This has been adapted from the ‘Summary and Conclusions’ chapter in the book.

Introduction

Les Minquiers. July 2016. Photo by Glyn Young

In 1998 the Jersey in the New Millennium government consultation document stated that Les Écréhous and Les Minquiers ‘may very well warrant SSI [Site of Special Interest] designation and even international recognition but there is an urgent need to recognise their unique character and the ecology/landscape/leisure use linkages in a “national park” style designation akin to that given to Les Mielles. The increase in leisure boating activity and the number of marinas on the adjacent French coast will subject these reefs to increasing people pressure with obvious knock-on ecological impacts’.

Since this was written all of Jersey’s offshore reefs have been designated as Ramsar (Wetlands of International Importance) areas and the terrestrial areas included within the Jersey National Park. Maîtresse Île is scheduled to become a Site of Special Interest (SSI) and has been subject to various management plans, laws, policies and multilateral environmental agreements.

This has drawn attention to the importance of the offshore reefs and yet, until recently, there remained a general lack of appreciation of their histories and natural histories, and an absence of coordinated study, management and monitoring. It was this knowledge gap that inspired a small team of amateur and professional naturalists to spend four years studying all aspects of Les Minquiers, from its history, archaeology and geology to its animal and plant life. Their results are published in the book, already described as ‘an achievement on a global scale’ by The Sunday Times environment correspondent (and author of End of the Line) Charles Clover.

Les Minquiers. April 2011. Photo by Glyn Young

Aside from providing a comprehensive overview of every aspect of Les Minquiers, the project’s results provide much of the basic information that is needed by local, national and perhaps international authorities to make decisions regarding the reef’s present-day management, as well as to develop strategies to safeguard its future.

Presented below is a summary of those results and conclusions that most concern the general environmental and ecological health of Les Minquiers, especially those which might have some relevance to the reef’s future management.

These should not be taken as an exhaustive summary of all the project’s results as much other information is provided in the book and a reading of the relevant chapters is recommended. Regardless of how the information derived from this project is used in the future, the authors would like to think that their work does fulfil the ‘urgent need to recognise the unique character’ of Les Minquiers, as requested by the States of Jersey in 1998.

A summary of physical and environmental change

Presented below is a summary of key facts and conclusions relating to the current and historical  environmental status of Les Minquiers. This includes aspects of the reef’s archaeology and oceanography but does not include summaries of information relating to the human and geological history of the reef unless it touches on ecological and environmental matters.

Physical Geography, Oceanography and Sedimentology

The general topography of Les Minquiers has probably changed little since the post-glacial sea level stabilised around 2,000 to 4,000 years ago. Much of the plateau is made of hard igneous rock about ten per cent of which is exposed at low water. There has been little opportunity for human activity to destroy or alter the bedrock and so many parts of the reef will present the same profile now as they did when the first Bronze Age hunters travelled to the reef in search of seals.

The main exception to this is Maîtresse Île and several nearby rocks whose physical profile has changed considerably following quarrying in the early nineteenth century. The removal of rock from the north-west and south-east of the island may have accelerated soil erosion by allowing breaking waves to access the area west of the huts. It is probable that some soil erosion had occurred prior to this but quarrying may have accelerated the process.

A second noticeable change in topography concerns the reef’s many sandbanks which build up against rocks or form in the lee of obstacles within tidal currents. An obvious example is the large sandbank known as Le Gris Banc which, since the time of the first hydrographic surveys, has moved steadily eastwards into an adjacent channel. This movement accelerated in the 1990s entirely closing what was once a navigable gap of around 300 metres. Other less strategic sandbanks, such as Le Banc du Turbot, may also have changed shape in recent decades. Although visually remarkable and a nuisance to boaters and chart makers, sandbank movement is probably part of a natural cycle of accumulation and erosion within the reef.

Le Gris Banc a sandbank at Les Minquiers which has moved 300 metres during the past decade. From Les Minquiers – A Natural History

Maîtresse Île

The small terrestrial area of Maîtresse Île has probably seen the greatest change of any place on Les Minquiers. Prior to the nineteenth century Maîtresse Île was a remote, largely untouched, vegetated island with no freshwater which was irregularly visited by fishermen. Then came the quarrymen and more organised fishing from La Rocque Harbour so that by the mid-nineteenth century around 18 stone buildings had been built which were permanently inhabited during the spring and summer months. It is probable that the fishermen managed the island’s vegetation (especially tree mallow) creating habitats for specialist coastal plants such as grasses. Throughout this time soil erosion continued to operate on the western and north-eastern edges of the island.

Maitresse Ile. April 2011. Photo by Glyn Young

Plant life

Following World War II the huts were abandoned, allowing plants and birds to take over. Renovation of the derelict buildings began in the 1970s and, by the 1980s, had led to a new phase of development and occupation by Jersey families. In 2016 just two hut sites remain undeveloped. As huts have been renovated and visitor numbers have increased, so the biology and ecology of Maîtresse Île has gradually changed. This was accelerated by the application of weed killer across the island in 1973 which removed an estimated 99% of all plant life. Erosion was enhanced immediately following this event leading to considerable soil loss.

Tree mallow (with mist net). April 2011. Photo by Glyn Young

Over the past century a total of 26 plant species have at some point been recorded from Maîtresse Île. The most species observed during an individual survey was 16 in 1973, immediately after the weed killer incident when, ironically, opportunistic weeds temporarily appeared. Currently there are eight known species with those plants that have disappeared during the past century mostly being grasses and short species such as thrift. Some of these (including thrift) may have been permanently removed by the weed killer incident while others were possibly crowded out by the tree mallow which currently dominates the island.

It is possible that tree mallow is naturally pervasive on Maîtresse Île and that, left to its own devices, this is the species that will proliferate and dominate. Other historically recorded species, such as grasses and thrift, may have been present only as long as the fishermen were resident and regularly clearing the tree mallow.

Aside from aesthetics, the most important roles of vegetation are to prevent soil erosion and provide food and shelter for wildlife. This is especially true for the island’s bird life with almost all the 92 recorded breeding and migratory species being dependent on the presence of tree mallow.

The destruction of vegetation exposes soil to the effects of waves, wind and rain, causing it to erode rapidly. Since 1928 Maîtresse Île has lost an estimated 50 per cent of its soil cover and it is soil erosion, above all else, that presents the greatest environmental threat to the island’s ecology. Soil provides an anchor for vegetation which is in turn needed by birds and invertebrate animals. Soil also supports hut foundations and contains archaeological material.

Although the issue of soil erosion has been raised several times by archaeologists, little has been done to address it. This should form a central part of any future management plans for Maîtresse Île, especially with regard to the way in which visitors and residents use the island. Without soil, Maîtresse Île will lose its wildlife, its infrastructure and its archaeology. Without soil, the central part of the island will be around a metre lower in height which will permit storm waves to sweep up from the south and east and cross the spine of the island.

Only the high points around the flagpole, Le Gabé and to the west of the toilet will be significantly above the high water mark. In such circumstances the huts and any terrestrial species are unlikely to survive, leaving Maîtresse Île a largely barren rock that, like La Grande Maison, would support only nesting birds, maritime algae and some lichens.

Nesting birds

Another notable biological change to have occurred in recent decades is in the use of Maîtresse Île by nesting birds. The discovery of seabird bones from the Bronze Age suggests that the island has been used as a nesting place for thousands of years. It is unlikely that seabirds would have nested successfully when fishermen were in residence as the nests would probably have been raided or scattered. After World War II birds did nest successfully as the ruined huts provided shelter for shags, gulls and other seabirds. Since renovation of the huts began in the 1970s, there has been a decrease in the number of species nesting so that currently it is only gull species which nest in any number on the rocky areas to the west and north of the huts although, in July and August 2015, a large number of Terns nested on the north of the island for the first time in living memory.

Les Maisons. Photo by Mick Dryden

Disturbance

In recent years weather, inadvertent disturbance and deliberate damage to nests has led to some poor breeding seasons on Maîtresse Île. For example, in 2014 all the gulls’ nests were deliberately destroyed early in the season leading to a disastrous breeding year for the birds. Additional monitoring of when, where and which species are nesting on the island might allow for a more targeted management during the nesting season. A second nesting site exists around the base of the beacon at La Grande Maison which seems to receive little human interference.

There have been many other events and incidents that have affected the ecology of Maîtresse Île in some way. Most of these result from individual acts of ignorance, such as clearing vegetation for camping or picnics, placing heavy machinery on the island and lighting barbecues on bare soil or next to huts. Other actions derive from ignorance or wanton destruction of property and the dumping of litter and chemicals are more deliberate acts.

An increased awareness of the fragility of Maîtresse Île’s ecology amongst visitors and residents will go some way to resolving these problems. Signs, websites and literature (such as posters and leaflets at marinas) should promote a greater understanding of Maîtresse Île and its ecology. There have also been issues around repairs and renovations on the island and it is recommended that future projects (whether by Jersey’s authorities or individuals) are made to adhere to tight management plans which avoid the risk of soil erosion, habitat destruction and pollution.

Climate change

One final and probably unavoidable issue facing Maîtresse Île is that of climate change and rising sea levels. Many different models and claims are made about the cause and visible effects of climate change but evidence does suggest that the global climate is undergoing a warming phase and that the sea level is rising. For low-lying islands and reefs this is not good news, as even small sea level rises risk increased erosion and marine inundation. This may be compounded by a predicted increase in the number and severity of storm surges as the warmer seas create and empower low pressure systems.

Maitresse Ile. April 2011. Photo by Glyn Young

Between October 2013 and March 2014 the coast of Europe was hit by a series of spectacular storms that rolled in off the Atlantic swamping and damaging coastlines along the English Channel. On Maîtresse Île these storms removed soil from the west of the island, damaged two of the seawalls and undermined the concrete area at the top of the slipway. Similarly, a storm surge in February 2008 damaged a wall and shifted large boulders across the slipway. As the sea level rises, so the destructive potential of waves will move higher up the island placing pressure on the sea defences and further increase the action of soil erosion. This issue is being addressed for Jersey’s sea defences and needs to be addressed for Maîtresse Île too.

The results from this project suggest that Maîtresse Île is facing several immediate threats, the most serious of which are issues relating to soil erosion, habitat/species loss and storm damage. These, and other threats, are best addressed through coherent management and monitoring of the island, investment in infrastructure maintenance, the cooperation of its principal users and raising awareness for visitors and potential visitors.

Maitresse Ile at Les Minquiers: soil erosion means it gets smaller every year. Les Minquiers – A Natural History

From Science

A new paper in Science by Franz Bairlein highlights how habitat degradation and loss, illegal killings, and climate change threaten European migratory bird populations.

The populations of migratory bird species that breed in Europe and overwinter in sub-Saharan Africa are declining considerably faster than those of nonmigratory resident species or of migratory species that overwinter in Europe. Likely factors are habitat changes due to changes in land use, illegal killing and taking along the northern African coasts, and climate-induced changes in timing of migration and breeding. However, not only European trans-Saharan migrants are declining fast. This holds also for North American long-distance migrants wintering in Central and South America. To halt these declines, preservation of remaining habitats and restoration of habitats both at breeding and no-breeding grounds is essential, as well as stopping illegal killing and taking of birds along their migration routes.

Illegal killing and taking

Every year, between 11 million and 36 million birds are killed or taken illegally in the Mediterranean region. The areas of greatest concern are in the eastern and central Mediterranean, with more than five million birds taken in both Egypt and Italy and an estimated one million each in Cyprus and Lebanon. Common migratory species such as Eurasian chaffinch, blackcap, and song thrush are most affected, but many less common migratory species are also taken in substantial numbers, including species of global conservation concern such as red kite and Eurasian curlew. On average, the annual illegal killings and takings of threatened or near-threatened migratory bird species amount to 1-3.5% of their populations – percentages that are very likely to have considerable impacts on the fate of these species. Illegal trapping can cause a collapse in population numbers within a short period of time. For example, the yellow-breasted bunting was abundant in its Eurasian breeding range until illegal takings in China caused an 84% population decline between 1980 and 2013.

Habitat degradation and loss

Many European migratory birds that overwinter in sub-Saharan Africa do not travel across those areas of the eastern Mediterranean most affected by illegal killings. Rather, they use a flyway across the western Mediterranean where illegal taking is much less intense. Other factors must play a role in their decline. A large number of European migratory species overwinter in the dry savannas of sub-Saharan Africa. Annual survival of many of these species correlates with rainfall in the Sahel zone. However, despite an increase in rainfall in the Sahel in recent decades, bird populations have continued to decline. Thus, factors other than rainfall must contribute to the population declines. Land-use and landcover changes are the most important. Between 1975 and 2000, agriculture increased by 57% in sub-Saharan Africa at the expense of natural vegetation, with nearly five million hectares of forest and non-forest vegetation lost per year. Most affected are the Sahel and Guinea Savanna zones where the majority of the Eurasian migratory species overwinter. An analysis of breeding-bird survey trends of 26 long-distance migratory species in the United Kingdom shows that wintering habitat is the most important determinant of population trends, with specialist species that occupy either open or woodland habitats in Africa showing declines.

Climate change 

Climate change is another major driver for biodiversity changes, including responses of bird populations. Many migratory species, including those that overwinter in sub-Saharan Africa, now arrive earlier at their spring breeding grounds. However, different organisms do not respond to climate change at the same pace, which has led to an ecological mismatch between some consumers and their prey. Dutch pied flycatchers, which overwinter in sub-Saharan Africa, do not arrive earlier at breeding grounds, but the populations of their insect food peak earlier as a result of warmer spring temperatures.

This mismatch between breeding and food availability has caused a decline of up to 90% in Dutch pied flycatcher population sizes. Climate change–induced changes in migratory bird populations are  evident in other species too, but their relative contribution to population changes in long-distance migrants wintering requires further clarification.

A global issue

In North America, the Breeding Bird Survey shows that half of the migratory bird species are declining; declines in long-distance Neotropical migrants are more pronounced than those of birds that migrate short distances. As for the European–African migrants, climate mismatch is a factor, but the long-distance migrants are particularly sensitive to habitat changes. Similar patterns might be expected for migratory birds in East Asia, but large-scale and long-term breeding bird population surveys, population trends, and nonbreeding habitat assessments are largely missing for that region.

Outlook

Any attempt to understand and ameliorate migratory bird losses must consider threats far away from their breeding sites. These threats could include killing and taking, human disturbance at staging sites, pesticide exposure, or collisions with human obstacles such as wind turbines and traffic. The most important drivers of population declines in migratory bird species are likely to be land-use changes and connected habitat degradation and loss, but few studies have investigated the specific impacts of land-use and land-cover changes on migratory bird populations in detail. Such studies are urgently needed to disentangle the various factors acting on populations of migratory species.

These studies must include carry-over effects, because conditions at nonbreeding grounds can affect reproductive success in the breeding season. Conversely, conditions at breeding grounds can affect nonbreeding fitness. In the red knot, climate-induced malnutrition at their Arctic breeding grounds resulted in shorter bills and reduced survival rates at their African wintering grounds. Future studies must also consider the role of stopover sites. Most long-distance migratory species rely on considerable fueling at such stopover sites before they embark on migratory flight, particularly if they need to cross oceans or deserts with no or limited feeding opportunities. The main fuel for migratory flights is fat. Consequently, migrants must accumulate enormous amounts of fat before migratory flights, some doubling their body mass within just a few weeks. To achieve that timed fueling, suitable habitats and food must be available at stopover sites. The effect of habitat loss and degradation at stopover sites on population trends in trans-Saharan migrants remains uninvestigated.

Consequently, future studies also need to clarify where species of conservation concern stop over and overwinter, and which migration routes they take. For example, British common cuckoos migrate along two routes to the same winter destination in sub-Saharan Africa. They face a much higher en route mortality when migrating along a western route than along an easterly route. Emerging technologies for tracking individual migratory birds throughout their annual cycle will reveal migratory routes and destinations in more detail than past bird marking, allowing more detailed and frequent assessment of the drivers of migratory species declines.

Existing data can, however, already be translated into immediate conservation actions to halt the decline of these migratory species. Wetlands can be protected from drainage; woody vegetation can be protected from grazing or even be replanted. Such efforts would not only support migratory birds but also the local biodiversity and livelihoods of local farmers and pastoralists. In addition, illegal taking and killing can be stopped. The required political instruments, such as the African–Eurasian Waterbird Agreement and the African–Eurasian Migratory Landbird Action Plan, are already in place. We just need to act, and we can if we wish.

From Rare Bird Alert

More than 300 individual puffins have been counted on Lundy Island this year, compared to just five birds ten years ago, thanks to a seabird recovery project.

Rats, which feast on the eggs and chicks of burrow-nesting birds such as puffin, were eradicated from the island between 2002 and 2004 as part of the Lundy Seabird Recovery Project, with the island being formally declared rat-free in 2006. See the BOTE report on the project in the Isles of Scilly and Lundy here

Other seabirds have also thrived, including Manx shearwater, with the most recent figures recording some 3,400 breeding pairs, from a low of only 300 pairs when the recovery project was planned and conducted.

Helen Booker, RSPB senior conservation officer, said:  “We expected Manx shearwater would benefit from rat eradication, and we have certainly seen that, but we were much less optimistic about puffin. Ten years ago its population had reached such a low level we worried whether it would survive, to see that puffin is now doing so well really is exciting.”

Becky Macdonald, the Landmark Trust’s warden on Lundy, said:  “The increase in Lundy’s seabird colonies, particularly the enigmatic puffin and elegant Manx shearwater, illustrates the importance of seabird recovery projects and the need to protect our seabird populations from controllable threats, such as predation by non-native mammals.”

The Lundy Seabird Recovery Project was mainly intended to boost the population of Manx shearwater, which were a higher conservation priority at the beginning of the century. But the puffin’s problems have multiplied since: the bird is struggling in northern Scotland, Orkney, Shetland, the Faroe Islands, Norway and Iceland, following a crash in the number of sandeels, the puffin’s preferred diet, probably triggered by warming sea temperatures.

There has been no breeding at all in some of the northern colonies in ten years. Whereas birds in places such as Lundy, but also in South Wales, Ireland, and elsewhere around the Irish Sea, have been able to exploit alternative food sources, such as pilchards and anchovies, numbers of which appear to be increasing in the southern parts of the puffin’s breeding range.

Dr Euan Dunn, RSPB seabird specialist, said: “puffins are facing serious threats, so it’s really important to have healthy colonies in places like Lundy in order for the bird to retain a resilient population, especially to combat the effects of climate change.

“In numerical terms, Lundy’s population is still modest but in terms of establishing a UK-wide halo of viable puffin breeding stations I attach real significance to this recovery.”

The Lundy Seabird Recovery Project was a partnership between the RSPB, the Landmark Trust, Natural England, and the National Trust.

John Holmes, Natural England’s area manager, said:  “This is fantastic news and a remarkable result over a relatively short time. It just shows what a concerted effort by a committed group of partners can achieve.”

Rob Joules, the National Trust’s general manager for Lundy, said:  “It’s great to reach the ten-year milestone of Lundy being rat-free and to see its wildlife thriving in direct response. This was an incredibly important and worthwhile project to be involved with and it’s great to know the lessons learned are being implemented on other offshore islands around the UK.”

Storm-petrel, which nests in small burrows or crevices among rocks, and whose breeding sites are also often plagued by rat predation, was recorded breeding on the island for the first time in 2014. Because the bird nests in inaccessible places precise figures are difficult to obtain, but up to 100 are now thought to be present.

From ScienceDaily

Climate change could make much of the Arctic unsuitable for millions of migratory birds that travel north to breed each year, according to a new international study.

University of Queensland School of Biological Sciences‘ researcher Hannah Wauchope said that suitable breeding conditions for Arctic shorebirds could collapse by 2070.

“This means that countries throughout the world will have fewer migratory birds reaching their shores,” Ms Wauchope said.

Arctic breeding shorebirds undertake some of the longest known migratory journeys in the animal kingdom, with many travelling more than 20,000km per year to escape the northern winter.

The bar-tailed godwit flies from Alaska to New Zealand in a single flight of 12,000 kilometres without landing.

The study predicts that, in a warming world, migratory birds will become increasingly restricted to small islands in the Arctic Ocean as they retreat north. This could cause declines in hard-hit regions and some birds could even completely change migratory pathways to migrate closer to suitable habitat.

“Climate change is also opening up the Arctic to threats such as mining and tourism, and we must make sure we protect key places for all Arctic species, including these amazing migratory birds,” Ms Wauchope said.

UQ’s Associate Professor Richard Fuller from the ARC Centre of Excellence for Environmental Decisions (CEED) said most migratory populations followed well-defined migratory routes. “This makes shorebirds an excellent group to investigate how climate change might impact breeding grounds and conservation actions that could address these impacts,” Associate Professor Fuller said.

The research modelled the suitable climate breeding conditions of 24 Arctic shorebirds and projected them to 2070. The researchers also examined the impact on Arctic birds of the world’s last major warming event about 6000 to 8000 years ago.

“Climatically suitable breeding conditions could shift and contract over the next 70 years, with up to 83 per cent of Arctic bird species losing most of their currently suitable area,” Ms Wauchope said. “This far exceeds the effects of the last major warming event on Earth, but genetic evidence suggests that even then the birds struggled to deal with the warming.”

She said that suitable climatic conditions are predicted to decline fastest in the areas with most species (western Alaska and eastern Russia), where Arctic birds are already becoming vulnerable to the “shrubification” of the tundra, and predators such as red foxes moving north.

You can read the abstract of the study Rapid climate-driven loss of breeding habitat for Arctic migratory birds here

From Birdwatch

A study tracking migrations of common cuckoos using tiny satellite tags, carried out by the British Trust for Ornithology (BTO) over the past five years, has made some very important discoveries. The results shed new light on the lives of migrating birds and point to some of the causes of this species’ dramatic population decline.

By fitting 42 male cuckoos with satellite trackers which allow each bird’s location to be logged, the researchers have confirmed that many of our cuckoos leave Britain in the autumn and fly to Italy, before crossing the Mediterranean and the Sahara to winter in Africa. The tags have revealed that the birds winter in the western part of the Congo rainforest, something that wasn’t known before.

Some birds, however, use a second route through Spain and on to West Africa, a strategy that was completely unexpected. Furthermore, after arriving in West Africa having crossed the Sahara, the birds make a left turn and make their way to the same central African wintering grounds as the birds that migrated via Italy. This is the first time that science has recorded birds taking two such distinct routes to the same destination; usually divergence in routes leads to the occupancy of different wintering grounds. Interestingly, all of the birds make their spring migration via the western route, regardless of the route used the previous autumn.

The unusual migration pattern allowed BTO scientists to assess the mortality rates associated with use of each of the two routes. Up to the point where the birds had completed their Sahara crossing there was a marked difference, with birds travelling via Italy surviving better than those going via Spain. This is the first time that differences in mortality have been attributed to differences in migration route. This new information may help to explain why cuckoo populations are in decline across much of Britain – the route that a cuckoo takes to get to its African wintering grounds could mean the difference between life and death.

Not only did survival rates of tagged birds differ between the two routes but so did the origins of the birds within Britain, leading to the third major finding. All of the birds tagged in Scotland and Wales, where the species is not so much in decline, took the more successful eastern route via Italy. Whereas across England, where 71 per cent of our breeding cuckoos has been lost during the last 25 years, local populations were made up of variable mixtures of birds taking either route.

Using information on cuckoo breeding populations from Bird Atlas 2007-11 and the BTO/JNCC/RSPB Breeding Bird Survey, the study found that across tagging locations in the UK, the proportion of birds using the less successful route via Spain correlates strongly with local population decline. This is the first time that mortality on migration has been linked to breeding population decline.

Dr Chris Hewson, lead scientist on the project at the BTO, said: “Understanding migratory birds and their population declines is very difficult because they may only be on their breeding grounds for a couple of months each year. Until recently, we had very limited information on where cuckoos and other long distance migrants went or what they did for the rest of the time. This study shows that by satellite-tracking them we can uncover not only their migration routes and wintering locations, but also information about patterns of survival that is potentially vital for understanding why they are disappearing so fast.”

Migrant birds such as the cuckoo fuel their migratory flights by storing fat in their bodies, and it seems that those feeding up in the western part of the Mediterranean might be finding this harder to do than those in the east. This could be as a result of the recent late summer droughts in Spain, reducing the abundance of the high-energy invertebrates that the cuckoos need to fuel a desert crossing. The study suggests these birds may undergo more fattening in the UK before they begin their migration than birds heading out via Italy. This would leave them especially vulnerable to the severe declines in moths (whose caterpillars are their main prey) in the south of England, where the birds breed.

There are currently 12 satellite-tagged cuckoos making their way to Africa. Anyone can follow and sponsor these birds as they make their way to the Congo rainforest during the next couple of months here.

Download the study Population decline is linked to migration route in the Common Cuckoo, a long distance nocturnally-migrating migrant here