The blackbird is in trouble.
Cherished by both Shakespeare and the Beatles for its melodious song, the blackbird has long captivated the hearts of Britons. However, this iconic songbird is now facing a worrying decline, prompting the British Trust for Ornithology (BTO) to call on the public to participate in a survey aimed at understanding the reasons behind this downturn.
Recent data reveals a sharp drop in blackbird populations, particularly in Greater London and southern England, a trend not observed in other parts of the UK. A significant factor in this decline is the Usutu virus, first detected in London during the summer of 2020.
Originating in South Africa and spreading across mainland Europe, the virus poses a serious threat to blackbirds in southeast England. The spread of this disease has been linked to climate change, as native UK mosquitoes, now more prevalent in warmer conditions, are capable of transmitting the virus.
In 2020, blackbird numbers in London plummeted by 50% compared to the previous year. Although there has been some recovery, the population remains 32% lower than in 2019. Nationally, blackbird numbers have fallen by 18% since the 1970s, with factors like habitat loss also playing a role.
Before the virus emerged, blackbird populations in London were already in slight decline. This has led scientists to explore other potential causes and seek solutions to reverse the trend.
Dr Hugh Hanmer, a 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. 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.”
The BTO survey aims to determine whether similar patterns are occurring in other UK cities and to assess differences between urban and rural populations.
As climate change continues to accelerate, the transmission of mosquito-borne diseases among birds is expected to rise. Through the survey, researchers hope to identify strategies to slow or halt the spread of such diseases and protect vulnerable bird populations.
The survey, open until October, will help BTO scientists gain insights into how blackbirds interact with different garden environments, their success in raising young, and the factors that influence disease risk in various urban settings.
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