Tag Archives: Climate change

Rising temperatures implicated in decline of the willow warbler

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From Rare Bird Alert

New research from BTO implicates rising temperatures in the steep decline of the willow warbler, one of the UK’s most tuneful harbingers of spring.

The study shows that willow warblers are doing better in Scotland, where temperatures are cooler. Evidence is building to suggest the population in southern Britain is a casualty of recent anthropogenic climate change.

BTO researchers used volunteer bird counts and habitat data from the BTO/JNCC/RSPB Breeding Bird Survey to separate the impacts of climate change and habitat change on willow warbler and chiffchaff populations. The analysis revealed that willow warbler numbers across the UK fell by 41% between 1994 and 2018, while those of the closely related chiffchaff grew by 133%. The picture was very different in Scotland, where temperatures are cooler than the UK average. North of the border, willow warblers increased by 77% and chiffchaffs by 244%.

During the period studied, the mean breeding season temperature was 12.7°C in England and 10.2°C in Scotland, close to the optimum breeding temperatures for chiffchaff (13.5°C) and willow warbler (11°C), respectively. However, UK Met Office data show that UK temperatures in the last 30 years have been about 1°C warmer than those during the three preceding decades. Changes like these can have impacts including producing a mismatch between young birds’ food requirements and insect abundance, an overall reduction in food abundance and shifts in habitat suitability.

The BBS habitat data showed that woodland and scrub, the preferred habitat for willow warblers and chiffchaffs, increased across the UK, with more habitat improvements in Scotland. However, this study showed that the increases in Scotland were more likely to be linked to climate change than habitat change.

Its UK decline means willow warbler has been on the Birds of Conservation Concern Amber List since 2002. With global temperatures forecast to keep rising, studies like this demonstrate the importance of long-term monitoring to ensure conservation measures are targeted effectively. More woodland and scrub, for example, would be more likely to be taken up by breeding willow warblers if it were concentrated in cooler areas of the UK.

Blaise Martay, BTO lead author on the paper, said: ‘We’ve discovered that these two superficially similar warblers have quite different temperature requirements during the breeding season. Climate change means willow warblers are now faring worse in warmer parts of the country, something that has implications for future conservation measures, such as habitat creation. The connection we’ve uncovered between temperature and breeding success suggests that conservation interventions for this species should be targeted in cooler parts of the UK.

She added, “I’d like to thank all the volunteers who take part in the BTO/JNCC/RSPB Breeding Bird Survey. Their records allow scientists like me to undertake analyses like this one and help us understand the pressures birds face as a result of climate change.’

In Jersey we have lost willow warbler as a breeding species although we still see birds in spring and autumn on migration. The annual north coast bird survey carried out in May or June each year when willow warblers and chiffchaffs would be nesting highlights the status of both these species. In Jersey, willow warbler is on the Red List. 

See the abstract of Breeding ground temperature rises, more than habitat change, are associated with spatially variable population trends in two species of migratory bird here

Infrastructure, hunting and climate change linked to huge migratory bird declines

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From Rare Bird Alert

Migratory birds are declining globally because of the way that humans have modified the landscape over recent decades – according to new research.

The new study reveals that population declines have been greatest among species that migrate to areas with more human infrastructure – roads, buildings, power lines, wind turbines – as well as higher population densities and hunting levels.

Habitat degradation and climate change have also played a part in driving long-term declines.

The research team hope their work will help inform how best to target conservation efforts. James Gilroy, from UEA’s School of Environmental Sciences, said: “We know that migratory birds are in greater decline than non-migratory species, but it’s not clear why.

“We wanted to find out where in their life cycles these migratory species are most exposed to human impacts.”

The team identified 16 human-induced threats to migratory birds, including infrastructure associated with bird disturbance and collisions, conversion of land from natural habitat to human land use, and climate change. Advances in satellite imagery allowed the team to map each of the 16 threats across Europe, Africa and Western Asia. The team also created the first ever large-scale map of hunting pressure across the region.

A total of 103 species of migrating birds were studied, including many rapidly declining species like turtle dove and the common cuckoo, using large-scale datasets.

The team calculated “threat scores” for factors such as habitat loss and climate change, across breeding locations, as well as non-breeding ranges. They then explored the relationships between these threat scores and bird population trends calculated from 1985 to 2018 by the Pan-European Common Bird Monitoring Scheme (PECBMS).

Claire Buchan from UEA, said: “One of the biggest impacts seems to be caused by things that would kill a bird outright – for example flying into a wind turbine, a building, being electrocuted on a powerline, hit by a vehicle or hunted. We found that exposure to these human-induced ‘direct mortality’ threats in the bird’s wintering ranges are reflected in population decreases in breeding birds.”

Aldina Franco, also from UEA, said: “Our findings are important because we need to understand where declining species are being most impacted by humans across their seasonal migrations. Pinpointing where birds are most exposed to these threats could help us target conservation actions.”

Download the paper Spatially explicit risk mapping reveals direct anthropogenic impacts on migratory birds here

Climate change and the UK’s birds

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From BirdGuides

A newly published study from the British Trust for Ornithology indicates that many of the UK’s seabird populations including that of the Atlantic puffin could plunge by as much as 90% by 2050 because of changes in the marine environment caused by rising temperatures, if global warming is not checked.

“This could represent a loss of over a million birds,” warned the BTO’s CEO, Professor Juliet Vickery. 

Increasing water temperatures are having a negative impact on sandeel numbers in British waters, the small fish which are the puffin’s main prey species – meaning that the breeding productivity of the puffins themselves is being adversely affected.

According to the BTO report, this is also affecting other seabirds, such as kittiwake; in all, 11 of our 20 breeding seabird species are regarded as being highly vulnerable to future climate change. The seabird numbers that the UK holds are internationally important.

Professor Vickery added: “If we are to hold onto our important bird populations then we need governments to make the right decisions for nature and the climate after COP26, and to invest in real action towards meeting these commitments. We will also need to continue to monitor the results of our actions – to evaluate what works and what doesn’t.”

Dr James Pearce-Higgins, Director of Science at BTO and author of the report, explained: “This new analysis reveals that, overall, one in five UK bird species will be affected by climate change. It is not just our seabirds that will be impacted; we will lose some of our best-loved summer visitors too. Once familiar migrants, such as common cuckoo and spotted flycatcher, have already seen their breeding populations more than halved during the last 25 years.”

Pearce-Higgins added: “Changing conditions here in the UK may have some impact, but the effects of changing weather patterns on the wintering grounds in Africa and along the migration routes used by these migrant birds may also be important. Projecting the future fortunes of these and other migrant birds is challenging given their complicated lives that cross continents. Securing their future will require international collaboration right along their flyway.”

Importantly, the report highlights those species that could be impacted by attempts to mitigate climate change, such as increased development of offshore renewables and widespread tree planting on upland habitats. Knowledge of bird numbers and distributions, gathered by BTO’s network of 60,000 citizen scientists, can help to inform how and where these approaches can be used in ways that minimise any potentially damaging impacts on declining species. We need to maintain our efforts to safeguard our seabirds, like the puffins, and other birds to ensure that they get as much support as we can give them.

The full report, Climate Change and the UK’s Birds, can be read here.