Garden owners in Edinburgh are urged to take part in a survey of blackbirds, to help monitor a killer virus linked to their decline.
The recent appearance of the mosquito-borne Usutu virus has been linked to the steep decline of the popular songbird in London and the southeast.
First identified in South Africa, the spread of the virus, which can be fatal to blackbirds, was first detected in England in the summer of 2020. Concerns are growing as it appears to be spreading, linked to climate change, and could eventually reach Scotland.
Scientists from the British Trust for Ornithology (BTO) want to understand the spread of Usutu virus and its potential impacts in other UK cities compared to smaller urban and rural areas.
The Blackbirds in Gardens Survey launched last year to try to map the rate of the species’ decline in London and to see whether similar population slumps were occurring elsewhere across the UK.
Initial results showed a north-south divide, with signs that blackbirds were doing better in the north, and particularly north-west England and in Scotland, while they continue to struggle in London and the wider south-east.
Researchers want more garden owners throughout the UK to get involved in this year’s survey, which runs until September, to help identify further notable changes.
Hugh Hanmer, Senior Research Ecologist with BTO said: “Blackbird numbers have been noted to be decreasing in Greater London for some time. However, from 2020 they started declining more strongly, which coincided with the detection of Usutu virus, which can be fatal for these familiar birds. There is now evidence of a wider decline in Southern England, not seen in other UK regions.
“This survey seeks to understand why this change is happening and if it is linked to the spread of Usutu, by better understanding how blackbirds use our gardens.”
He added: “At this stage there is no evidence to suggest that Usutu virus is affecting blackbirds in Scotland. However, the rate of impact detected in southern England, and especially around London, gives us real cause for concern.
“We need people to help us gather data about blackbirds in Scottish gardens, particularly those in more urban and suburban areas, so that we may be able to understand why blackbirds are doing so much worse in London compared to elsewhere.”
The survey will help BTO scientists better understand how blackbirds’ use of different garden types varies, disease transmission risk, and how successfully young are raised, at different levels of urbanisation, from rural to urban gardens.
Usutu is typically spread by bird-biting mosquitoes, which rarely bite humans. When it does occur, human infection is often asymptomatic, and there have been no human cases of Usutu detected in the UK to date.
Although the risk to humans from Usutu virus is extremely low, this is the first time in modern history that a mosquito-borne viral zoonosis — a disease that can be transmitted from animals to humans — has emerged in the UK.
The BTO survey is part of a wider partnership project, run 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 to understand the emergence and transmission of mosquito-borne viruses of wild birds in the UK, which are expected to increase as a result of climate change.
Dr Arran Folly, senior scientist with APHA and Vector-Borne RADAR project lead, said: “With Usutu virus now endemic in southeast England, outbreaks of mosquito-borne diseases are expected to grow in the UK, especially as temperatures rise due to climate change.
“Through our Vector-Borne RADAR project, we are working to gain a clearer picture of emerging mosquito-borne viruses.
“The insights from BTO’s Blackbirds In Gardens survey will be essential for understanding how this virus might be impacting blackbird populations. I encourage all garden owners to get involved and help us track this virus.”
BTO is asking for anyone with access to a garden to take part in the Blackbirds in Gardens survey, which runs until September. People can sign up at www.bto.org/blackbirds
