Help blackbirds as virus threatens to decimate numbers

A much-loved garden bird, blackbirds have been a part of UK culture for centuries – from the nursery rhyme ‘Sing a Song of Sixpence’, to the Victorian poetry of Thomas Hardy and that iconic 60s chart hit by The Beatles.

But now, a new threat has blackbird populations plummeting and scientists from the British Trust for Ornithology working to better understand the spread and potential impact of the disease responsible – the Usutu virus.

Usutu virus has been linked to mass blackbird mortality, with UK birders – especially in the Greater London area – reporting that blackbirds are noticeably less abundant in the last few years. As the disease spreads, scientists and ecologists are calling on the public for help.
 

What is Usutu virus?

Usutu virus, also known as USUV, is a mosquito-borne disease that can be fatal to blackbirds. First found in the UK in London in 2020, the virus is now spreading across southeast England.

The virus was first identified in South Africa, and has been present in mainland Europe for around 30 years. Its spread has been linked to climate change, with native UK mosquitoes being able to transmit the virus during warmer times of year.

Usutu virus is carried by bird-biting mosquitoes that rarely bite humans. If this does occur, human infection often has no symptoms, and no human cases of Usutu virus have so far been detected in the UK.

Emergence of Usutu in the UK follows rapid declines in greenfinch and chaffinch populations due to a separate, parasitic disease, trichomonosis, with the BTO reinforcing the importance of keeping bird feeding stations clean and hygienic.
 

How you can help blackbirds

• Minimise unnecessary standing water in your garden where mosquitoes could breed: stand wheelbarrows up when not in use to avoid rainwater collecting, put away any plant saucers when not in use, ensure gutters are kept clear of blockages, and ensure lids are fitted to water butts (this also reduces the risk of wildlife drownings).

• Wash out bird baths regularly, refilling with clean tap water. Clean and disinfect bird feeders every week to remove any build-up of food and droppings, and sweep the area around and below any bird feeders and tables. Maintaining good hygiene at the feeding area will also help to reduce the spread of other bird diseases such as the trichomonosis that has decimated greenfinch and chaffinch populations.

• Keep an eye out for unusual behaviour or deceased blackbirds – symptoms include lethargy, weakness, loss of coordination and seizures. You can report signs of disease, or finding a dead blackbird, to Garden Wildlife Health. Although Usutu is not a notifiable disease, meaning it doesn’t officially have to be reported, this will help scientists track its spread. If you need to move or handle a dead blackbird, or nearby feathers or droppings, wear disposable gloves or a plastic bag over your hand and thoroughly wash your hands with soap and water afterwards.

• Take part in the BTO’s blackbird survey between May and October to report how blackbirds are doing in your garden and help scientists keep track of population numbers. Sign up here.

What are the symptoms of Usutu virus?

According to Garden Wildlife Health and the Dutch Wildlife Health Centre, symptoms in blackbirds include:

• Weakness and lethargy
• Poor coordination or balance
• Reluctance to fly
• Drooping head and/or wings
• Ruffled or puffed-up feathers
• Gasping for breath
• Seizures

Know your blackbirds

Male blackbird: black plumage, pronounced golden yellow or even orange-yellow beak and eye ring

Female blackbird: dark brown, faint yellow ring around eye, yellowing to beak

Juvenile blackbird: paler brown with obvious paler or golden speckling, beak has less yellow, may have some fluff