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Suffolk residents urged to take part in BTO survey on blackbirds’ rapid decline





Members of the public are being urged to assist scientists to discover the reasons behind the rapid decline of blackbirds.

The British Trust for Ornithology (BTO), based in Thetford, has launched a survey to investigate the plight of this popular UK garden bird, which is believed to be becoming increasingly scarce due to a mosquito-borne virus.

First identified in South Africa, the Usutu virus was detected in the UK for the first time in London during the summer of 2020.

An adult male blackbird. Picture: Gray Images
An adult male blackbird. Picture: Gray Images

Residents in Suffolk are encouraged to participate in the survey if they have access to a garden and can identify blackbirds by sight - including distinguishing between adult males, adult females and juveniles.

Dr. Hugh Hanmer, senior research ecologist with BTO, said: "Blackbird numbers have been decreasing in Greater London for some time.

“However, from 2020 they started declining more strongly, which coincided with the detection of Usutu virus.

The blackbird population's rapid decline has been linked to a mosquito-borne virus. Picture: Sarah Kelman
The blackbird population's rapid decline has been linked to a mosquito-borne virus. Picture: Sarah Kelman

“There is now evidence of a wider decline in southern England, not seen in other UK regions.

“The BTO survey seeks to understand why this change is happening and to identify any link to the emergence of Usutu virus.

“By better understanding how blackbirds use our gardens, we hope to halt the declines.”

This virus poses a significant threat to blackbirds and has been linked to climate change as warmer temperatures allow UK mosquitoes to transmit the virus.

Residents who have access to a garden are being urged to take part in a survey. Picture: Amy Lewis / British Trust for Ornithology
Residents who have access to a garden are being urged to take part in a survey. Picture: Amy Lewis / British Trust for Ornithology

Although the risk to humans from the Usutu virus is low, this marks the first instance in modern history where a mosquito-borne viral zoonosis (a disease that can be transmitted from animals to humans) has emerged in the UK.

This BTO survey is part of a wider partnership project, being run in conjunction with the Animal and Plant Health Agency (APHA), the Zoological Society of London (ZSL) and the UK Health Security Agency (UKHSA).

The project, Vector-Borne RADAR, is funded by UK Research and Innovation and Defra and aims to to understand the emergence and transmission of mosquito-borne viruses of wild birds in the UK.

To sign up and find out more, visit https://www.bto.org/our-science/projects/blackbirds-gardens/taking-part.

Dr Arran Folly, senior scientist with APHA and Vector-Borne RADAR project lead, said: “Outbreaks of mosquito-transmitted diseases like Usutu virus, which is now endemic in south-east England, are likely to increase in the UK especially as temperatures warm in the wake of climate change.

“The findings from the BTO survey will be invaluable in building a better understanding of how the virus could be impacting our blackbird populations.

“I would urge any garden owners to take part and help us keep track of this virus."