Built infrastructure, hunting and climate change linked to huge migratory bird declines
University of East Anglia
A new
study published today 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.
Dr 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
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).
Dr C,laire
Buchan from UEA's School of Biological Sciences, said: "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.
"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."
Dr 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).
Researchers working on this project have received funding from the Natural Environment Research Council (NERC), the European Commission and the Portuguese Foundation for Science and Technology.