The Virus Threatening Our Blackbirds
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The Usutu virus (USUV) is an emerging mosquito-borne virus that poses a significant threat to bird populations in Europe, particularly blackbirds.
Originally identified in South Africa in 1959, the virus was first detected in Europe in 1996 and has since spread across many countries, including Germany, Austria, the Netherlands and the UK.
USUV is a flavivirus, related to West Nile virus and Zika. It is transmitted primarily through the bites of infected mosquitoes. Birds act as the main hosts, while mosquitoes spread the virus between them. Occasionally, mammals such as humans can be infected, though such cases are rare and usually mild or asymptomatic.
For birds, however, the virus can be deadly. Blackbirds are especially vulnerable, with high mortality rates observed in affected populations. Symptoms in birds may include disorientation, weakness and loss of coordination. Infected blackbirds often die within a few days, and outbreaks have led to noticeable declines in local populations.
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Warmer climates and changing ecosystems are helping USUV expand its range. Milder winters allow mosquitoes to survive and reproduce earlier in the season, increasing the chances of transmission. The virus can also travel via migratory birds and the accidental transportation of mosquitoes through human activity.
In some parts of Europe, blackbird populations have dropped significantly after outbreaks. In the UK, the virus was first detected in wild birds in 2020, and ongoing monitoring suggests it may become more widespread if not checked.
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While we cannot completely eliminate the risk of USUV, there are steps we can take to support bird populations and reduce the spread of mosquito-borne diseases:
Remove Standing Water
Mosquitoes breed in stagnant water. Empty birdbaths, plant trays, gutters and containers regularly to disrupt their breeding cycle.
Clean Feeders and Baths
Maintain clean bird-feeders and birdbaths to prevent the spread of other diseases and reduce stress on birds, which can make them more susceptible to infection.
Report Sick or Dead Birds
If you find blackbirds or other wild birds that appear ill or have died suddenly, report them to local wildlife health authorities or ornithological societies. This helps track outbreaks and monitor the spread of the virus.
Support Biodiversity
Planting a variety of native plants can help create a healthier ecosystem that supports insect-eating birds and natural mosquito predators such as dragonflies and bats.
Stay Informed
Follow updates from wildlife organisations and public health bodies. Citizen science efforts, such as those run by the British Trust for Ornithology or similar groups, can make a real difference.
