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

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