A study published June 25 reveals that bird population declines have been greatest among species that migrate to areas with more human infrastructure — roads, buildings, power lines, wind turbines, etc. — as well as higher human population densities and hunting levels.
Habitat degradation and climate change have also played a part in driving long-term declines, according to the study from the University of East Anglia in England.
The research team hope their work will help inform how best to target conservation efforts.
“We know that migratory birds are in greater decline than non-migratory species, but it’s not clear why,” said James Gilroy, a co-author of the study and a scientist at UEA’s School of Environmental Sciences. “We wanted to find out where in their life cycles these migratory species are most exposed to human impacts.”
The research 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 the 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).
Targeting conservation actions
“We found that human modification of the landscape in the birds’ distribution ranges in Europe, Africa, and Western Asia is associated with declining numbers of over 100 Afro-Eurasian migratory birds,” said Claire Buchan from UEA’s School of Biological Sciences. “When we talk about modification of the landscape, we mean things like roads, buildings, powerlines, wind turbines – anything that isn’t naturally there.
“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’s School of Environmental Sciences, 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.”
This research was led by UEA (UK) in collaboration with the University of Porto and the University of Lisbon (both Portugal), and the Czech Society for Ornithology (Czech Republic).
Thanks to the University of East Anglia for providing this news.
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