Feed the birds? Scientists highlight risks of disease at garden bird feeders

No.:  2018-07
March 2018

Collaborative 25-year ZSL/BTO study stresses importance of feeding while investigating evolving threats to wild birds

Wild birds are at risk of a number of serious diseases at our garden bird feeders, according to a collaborative study led by scientists from international conservation charity ZSL (Zoological Society of London) and published in the journal Philosophical Transactions of the Royal Society B.
 
The study found that while there are multiple benefits of additional food resources for wild birds, particularly during the harsher winter months, garden feeding can also promote the transmission of some diseases – not least by encouraging birds to repeatedly congregate in the same location, often bringing them into regular contact with other species they wouldn’t otherwise interact with so closely in the wider environment. Risks can be increased if hygiene at feeding stations is poor, allowing stale food, food waste and droppings to accumulate.
 
The research, conducted in partnership with the British Trust for Ornithology (BTO) and Fera Science Ltd, analysed more than 25 years’ worth of data on the occurrence of wild bird health threats, focusing on protozoal (finch trichomonosis), viral (Paridae pox) and bacterial (passerine salmonellosis) diseases. Members of the public contributed their observations via national ‘citizen science’ projects, highlighting the ongoing importance of these surveys in helping scientists track the evolving health threats facing garden wildlife.
 
Commenting on the study, lead author Dr Becki Lawson from ZSL’s Institute of Zoology said, “Our study shows how three of the most common diseases that affect British garden birds have changed both dramatically and unpredictably over the past decade, both in terms of the species they affect and their patterns of occurrence."
 
“Both finch trichomonosis and Paridae pox have emerged recently, causing disease epidemics affecting large numbers of birds, while passerine salmonellosis – previously a common condition – appears to have reduced to a very low level. These conditions have different means of transmission – so deepening our understanding of disease dynamics will help us develop best practice advice to ensure that feeding garden birds also helps to safeguard their health”.
 

The study makes a number of evidence-based recommendations to maximise the benefits but minimise the potential risks associated with feeding wild birds. When disease outbreaks do occur, people are encouraged to report their observations (e.g. lethargy or unusually fluffed-up plumage) to the Garden Wildlife Health (GWH) project; seek veterinary guidance; and consider a temporary halt to garden feeding in order to encourage birds to disperse, reducing the risk of  further disease spread.
 
Commenting further, co-author Kate Risely from BTO said, “We’re calling on everyone who feeds wild birds to be aware of their responsibilities for preventing disease. Simple steps we’d recommend include offering a variety of food from accredited sources; feeding in moderation, so that feeders are typically emptied every 1-2 days; the regular cleaning of bird feeders; and rotation of feeding sites to avoid accumulation of waste food or bird droppings."
 
Anyone can join the battle against wildlife disease by contributing vital data to the nationwide GWH project, a collaboration between ZSL, BTO, Froglife and the Royal Society for the Protection of Birds (RSPB). Find out more, including further best-practice advice for minimising disease risks, via this link: https://www.gardenwildlifehealth.org/

Notes to editors
Related images available here: https://zslondon.sharefile.com/d-s0ced19ea22e4763b
 
Zoological Society of London (ZSL)
Founded in 1826, ZSL (Zoological Society of London) is an international scientific, conservation and educational charity whose mission is to promote and achieve the worldwide conservation of animals and their habitats. Our mission is realised through our ground-breaking science, our active conservation projects in more than 50 countries and our two Zoos, ZSL London Zoo and ZSL Whipsnade Zoo. For more information visit www.zsl.org
 
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.

Fera Science Ltd
Fera Science Limited, formerly the Food and Environment Research Agency, is a joint private/public sector venture between Capita plc and Defra. Based on the National Agri-Food Innovation Campus in Sand Hutton, Fera’s vision is to be a leading supplier of scientific solutions, evidence and advice across the agri-food supply chain. Employing more than 350 scientists, Fera analyses over 90,000 samples and publishes over 100 peer-reviewed scientific papers per year. It turns expertise and innovation into ways to support and develop a sustainable food chain, a healthy natural environment, and to protect the global community from biological and chemical risks. Find out more at www.fera.co.uk.
 
Use of ZSL images and video
Photographs, video or graphics distributed by ZSL (Zoological Society of London) to support this media release may only be used for editorial reporting purposes for the contemporaneous illustration of events, things or the persons in the image or facts mentioned in the media release or image caption. Reuse of the picture or video requires further permission from the press office of ZSL.
 
Garden Wildlife Health
Garden Wildlife Health is a collaborative project between ZSL (Zoological Society of London), the British Trust for Ornithology (BTO), Froglife and the Royal Society for the Protection of Birds (RSPB), which aims to safeguard the health of British garden wildlife by conducting research into the causes and trends of diseases in a variety of species (garden birds, amphibians, reptiles and hedgehogs), and investigating their impacts on the affected populations (www.gardenwildlifehealth.org). The project receives funding from the UK Department for the Environment Food & Rural Affairs and Welsh Government through the Animal Plant & Health Agency’s Diseases of Wildlife Scheme Scanning Surveillance Programme (Project ED1600), the Esmée Fairbairn Foundation, and the Universities Federation for Animal Welfare.
 
Whilst the risks to public health are considered very low, sensible hygiene precautions, such as cleaning feeders outdoors with dedicated equipment and not in the kitchen; hand washing after feeding birds; and not handling wild bird carcasses directly are recommended as a routine.
Disease factsheets on the common disease conditions affecting British garden birds are available at the website, www.gardenwildlifehealth.org.