Northern bird found to be more resilient to winter weather

28 Jun 2016 | No. 2016-24

New research, published today in the Royal Society journal Open Science, reveals that one of our most widespread songbirds – the Wren – varies in its resilience to winter weather, depending on where in Britain it lives. Scottish Wrens are larger than those living in southern Britain, and more resilient to hard winter frosts.

Populations of small birds may decline following periods of cold winter weather, something that is probably linked to low temperatures and difficulties in finding sufficient insect prey. We might expect populations inhabiting regions where winters are more severe to show some form of adaptation, and this is exactly what researchers at the British Trust for Ornithology (BTO) have found in a study of one of our smallest songbirds, the Wren.

BTO researchers used information on Wren populations that had been collected by volunteers participating in the BTO/JNCC/RSPB Breeding Bird Survey, the main scheme for monitoring the population changes of the UK’s common breeding birds. The researchers found that Wren populations were susceptible to severe winter weather, measured in terms of the number of days with a ground frost. However, northern populations were found to be resilient to winters with up to 70% more frost days than southern populations, suggesting a degree of local adaptation.

James Pearce-Higgins (BTO Director of Science and one of the authors) commented "This work indicates that each Wren population is closely adapted to its local climate; there was a close correlation between the historic regional climate and the degree to which the population was resilient to severe winters.

Using information collected by bird ringers, the team also found that Wren body mass was approximately 5% lower in the warmest (south-west) than in the coldest (east Scotland) region. As lead author Catriona Morrison, from the University of East Anglia, noted "Large individuals are likely to be favoured in colder regions due to the thermal advantage of larger  size and their ability to store more body fat, and our findings match the pattern seen more widely across other species – a pattern known as Bergmann’s rule."

The findings of this study have particular relevance to our understanding of how birds and other species respond to climate change. Although this work shows that wren populations may adapt to at least some change in temperature, they are short-lived and therefore probably more adaptable than most other bird species. Ultimately, the ability of species to cope with climate change will depend upon whether the future rate of warming exceeds their ability to adapt.

Notes for Editors

  1. Catriona A. Morrison, Robert A. Robinson & James W. Pearce-Higgins. 2016. Winter wren populations show adaptation to local climate. Royal Society Open Science 3. 160250. 
  2. The Wren is one of Britain’s smallest birds. It is also one of the most widespread, occupying a wide range of habitats and only absent from some of the highest-altitude areas within Scotland.
  3. James Pearce-Higgins is Director of Science and Rob Robinson is Associate Director – Research, both at the British Trust for Ornithology (BTO). The BTO is the UK's leading bird research charity. A growing membership and up to 60,000 volunteer birdwatchers contribute to the BTO's surveys, collecting information that underpins conservation action in the UK. The BTO maintains a staff of 100 at its offices in Thetford, Stirling, Bangor (Wales) and Bangor (Northern Ireland), who analyse and publicise the results of surveys and projects. The BTO's work is funded by BTO supporters, government, trusts, industry and conservation organisations.
  4. Catriona Morrision is a post-doctoral researcher, based at The University of East Anglia. The University of East Anglia (UEA) is among the top 1% of universities globally (Times Higher Education World Rankings 2015-16) and placed 10th in the UK for the quality of its research output (Research Excellence Framework 2014). Also known for its outstanding student experience, it has achieved a Top 10 rating in the National Student Survey every year since the survey began. UEA is a leading member of the Norwich Research Park - one of Europe’s largest concentrations of researchers in the fields of environment, health and plant science.
  5. The BTO/JNCC/RSPB Breeding Bird Survey (BBS) is the main scheme for monitoring the population changes of the UK’s common breeding birds. It is a national volunteer project aimed at keeping track of changes in the breeding populations of widespread bird species in the UK. Wild bird populations are an important indicator of the health of the countryside, and knowing to what extent bird populations are increasing or decreasing is fundamental to bird conservation. The BBS is run by the British Trust for Ornithology (BTO), and jointly funded by the BTO, the Joint Nature Conservation Committee (JNCC, the statutory adviser to Government on UK and international nature conservation, on behalf of Natural Resources Wales, the Council for Nature Conservation and the Countryside, Natural England and Scottish Natural Heritage) and the Royal Society for the Protection of Birds (RSPB).
  6. The Ringing Scheme is funded by a partnership of the BTO and the JNCC on behalf of the statutory nature conservation bodies (Natural England, Natural Resources Wales, Scottish Natural Heritage and the Department of the Environment Northern Ireland). Ringing is also funded by The National Parks and Wildlife Service (Ireland) and the ringers themselves. The BTO supports ringing and nest recording for scientific purposes and is licensed by the statutory nature conservation bodies to permit bird ringing and some aspects of nest recording. All activities described are undertaken with appropriate licences and following codes of conduct designed to ensure the welfare of birds and their nests are not adversely affected.

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