Small birds, big message

Eurasian Wren and its close American relative, Winter Wren, are fairly ubiquitous across the northern hemisphere, but this has not stopped the species complex from being affected by climate change. Photo: Sonja Kübelbeck (commons.wikimedia.org).
Eurasian Wren and its close American relative, Winter Wren, are fairly ubiquitous across the northern hemisphere, but this has not stopped the species complex from being affected by climate change. Photo: Sonja Kübelbeck (commons.wikimedia.org).
A new study has confirmed that common birds are powerful indicators of the threat from climate change across the northern hemisphere.

From Europe to North America, combined data shows coherent and substantial changes in detriment to cold-adapted species undergoing the processes of climate change.

A common sight in many gardens, Eurasian Wren, cocking its short, stubby tail and flitting from twig to twig, is known for its restless nature – many readers will be familiar with the rapid chittering of its alarm call, a remarkably loud voice for such a small bird. According to new research published today in the journal Science, the tiny brown bird is sending a bigger message, one that makes its restlessness certainly seem more apt.

An international team of researchers, led by Durham University and including scientists from the RSPB (BirdLife in the UK) and BirdLife International, found that populations of bird species expected to do well due to climate change had substantially outperformed those expected to do badly over a 30-year period from 1980 to 2010.

The study shows that common bird populations in Europe and North America are messengers of climate change, as they are strongly responding to alterations in temperatures. Winter Wren (the North American equivalent of Eurasian) and American Robin, which are seen in gardens or local woodlands are precious indicators of their ecosystems and of our planet’s climate.

The research, conducted in collaboration with the RSPB and the United States Geological Survey (USGS), is the first real demonstration that climate is having a similar large-scale influence on the abundance of common birds in widely separated parts of the world. The familiar birds found in different countries and continents seem to be sharing with us a common message about climate change. This phenomenon is affecting different animal species in various ways: warm-adapted species generally fare better than cold-adapted species, for example.

The team found a clear difference in the average population trends of bird species either advantaged or disadvantaged by climate change in both continents. In Europe, species such as Eurasian Wren have been increasing in northern areas where winters are becoming milder, but declining in some southern countries where summers have been getting hotter and drier.

The British population of Dartford Warbler, which used to be limited to Dorset, has increased eight-fold since the early 1980s while declining in Spain, as predicted from changes in weather relative to the species’ preferences. American Robin, found across much of continental North America, has declined in southern states such as Mississippi and Louisiana but increased in north-central states such as the Dakotas.

The study’s lead authors, Dr Stephen Willis and Dr Philip Stephens of Durham University, believe the findings show there has been a large-scale, consistent response by bird populations to climate change on both continents. According to Dr Willis, the research: “helps us to understand where climate change is affecting populations and to understand the causes of population changes of common birds, that might also be affected by factors such as habitat loss and agricultural intensification.”

Co-author Dr Stuart Butchart, Head of Science at BirdLife International, the study: “adds to the body of evidence that many of the world’s birds have already been impacted by climate change, mostly in negative ways. It is a further warning that actions are urgently needed to minimise climate change, and to help nature and people adapt.”

BirdLife International and the National Audubon Society jointly released a report entitled The Messengers at the Paris meeting of the UN Convention on Climate Change in late 2015. Today’s paper in Science extends some of the work synthesised in The Messengers, and shows that similar impacts are being felt across both Europe and North America.
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