Number of blackbirds in British gardens is plummeting because of mosquito-borne virus, charity warns

The number of blackbirds in our gardens is falling due to a mosquito-borne virus, a charity has warned.

The population is declining, especially inland London where the total fell by 50 percent in 2020, according to the British Trust for Ornithology (BTO).

The numbers recovered, but are still about 32 percent lower than in 2019.

It has been linked to the spread of the Usutu virus climate change. It was first identified in South Africa before being discovered in mainland Europe three decades ago, and then in the UK in the summer of 2020.

Native British mosquitoes can transmit the virus in warmer periods and humans can also contract it, although no cases have been identified in Britain.

Blackbird populations are declining, especially in London, where totals fell by 50 percent in 2020, according to the British Trust for Ornithology

Scientists are trying to better understand the extent and spread of the Usutu virus and what its potential impact could be on British Blackbirds

The government said the Usutu virus in Croatia led to the deaths of two people with weakened immune systems Italy.

The BTO added that while the risk was low, ‘This is the first time in modern history that a mosquito-borne viral zoonosis (a disease that can be passed from animals to humans) has emerged in the UK.’

Now scientists are trying to better understand the extent and spread of the Usutu virus and what its potential impact could be on British Blackbirds.

Researchers are keen to see if something similar happens in other major cities in Britain, and how this compares to smaller urban and rural areas.

The BTO is calling on people to take part in the Blackbirds in Gardens Survey to help their scientists better understand how Blackbirds use different types of gardens and what factors can influence the risk of disease transmission.

Importantly, the study also seeks to determine how successful the birds are at raising young, especially at different levels of urbanization, from rural to urban gardens.

Dr. Hugh Hanmer, senior research ecologist at BTO, said: ‘Blackbird numbers have been declining in Greater London for some time.

‘However, from 2020 onwards they started to decline more sharply, coinciding with the detection of the Usutu virus.

‘There is now evidence of a wider decline in southern England, which has not been seen in other UK regions.

‘The BTO investigation seeks to understand why this change is happening and to identify any links to the emergence of the Usutu virus.

‘By better understanding how Blackbirds use our gardens, we hope to halt the decline.’

Native British mosquitoes can transmit the Usutu virus in warmer periods and humans can also contract it, although no cases have been identified in Britain

Blackbird numbers in London fell by 50 percent in July 2020. They recovered slightly, but are still about 32 percent lower than in 2019.

Dr. Arran Folly, senior scientist at the APHA and Vector-Borne RADAR project leader said: ‘Outbreaks of mosquito-borne diseases such as the Usutu virus, which is now endemic in south-east England, are likely to increase in Britain, especially now temperatures in the UK are rising. the aftermath of climate change.”

He added: ‘I would appeal to all garden owners to take part and help us keep a lid on this virus.’

BTO is asking anyone with access to a garden to participate in the survey.

Go to to sign up www.bto.org/blackbirds-gardens