All homeowners who have blackbirds in their garden are being urged to make a vital change to help the species. Experts say that populations of the bird are ‘dwindling’ as a mosquito-borne virus spreads from London, reaching as far west as Dorset.
The Usutu virus, first identified at the river in South Africa, has been decimating blackbirds since it was first detected in the UK five years ago. From the initial cases in Greater London, where blackbird numbers have plummeted 40 per cent since 2018, the virus has entrenched itself across the southeast.
It has now spread as far west as Portland Bill and east across East Anglia, according to preliminary findings from a garden survey conducted by the British Trust for Ornithology (BTO) last year. While it hasn’t reached the Midlands yet, experts believe there’s no reason to think a northward spread won’t happen, the Times reported.
Blackbird numbers have dropped by about 10 per cent in East Anglia and the southeast of England, and about 5 per cent in southwest England, as of summer last year. Hugh Hanmer, a senior research ecologist at the BTO, suggested several ways gardeners could help support blackbirds.
Wildlife expert Hanmer has highlighted the importance of being vigilant about potential mosquito breeding grounds, such as uncovered water butts, especially with the rise in mosquito-borne diseases. “We’re interested in whether water butts are a potential source of mosquito breeding. So we may encourage people to cover their water butt to stop them getting in, as that’s a standard approach in countries where mosquito-borne disease is a serious problem. Wildlife-friendly gardening will help, such as ponds, native bushes and trees, not paving everything,” Hanmer remarked.
Climate change is exacerbating the situation by fostering conditions favourable to the viruses’ survival and expansion. Mr Hanmer, discussing the influence of well-maintained gardens on blackbird numbers in London, found that more mature, green gardens with ponds fared better than others. Contrary to initial concerns, ponds have not been proven to be propitious environments for mosquitoes.
“Ponds are useful. We don’t want people to get rid of their pond,” advised Hanmer. Research indicates blackbirds could face a dramatic population decline in the UK, potentially up to 40 per cent, though there is hope that some may develop genetic resistance.
The profound affection Britons have for feeding garden birds has resulted in the UK hosting an immense population of garden birds compared to other European nations. With approximately 5 million breeding pairs of blackbirds across the country, the impact of declines in their numbers could be monumental.
“We’re not going to lose blackbirds, but we could have a lot fewer of them,” warned Hanmer, highlighting the lack of room for complacency as the virus menacing our feathered friends is just one of many pathogens threatening UK species. The expert stressed blackbirds’ importance in consuming pests like slugs.
The British Trust for Ornithology has previously said: ““Blackbirds are a common bird in gardens across the UK, from rural areas to the hearts of cities. However, in recent years and particularly since 2020, birdwatchers have reported fewer birds being seen in their gardens, especially in London.
“This recent decline has been linked to the appearance of Usutu virus, a new mosquito-borne virus in the UK which is often fatal to blackbirds. It was first detected in the UK in London in the summer of 2020, and appears to have since started to spread further in southern Britain. It is prevalent on the near-Continent and its spread has been linked to climate change, which has benefited the mosquitoes which spread the virus.”
Yet, while Usutu virus shares similarities with West Nile virus, which poses serious risks to humans, Arran Folly from the government’s Animal and Plant Health Agency considers it to represent “very low” risk to people, noting an absence of human infection cases within the UK. Folly’s team has been meticulously tracking the virus’s trajectory by capturing up to 30,000 mosquitoes annually and joining bird ringers to assess birds for virus evidence and antibodies resulting from bites.
Since its first detection in Britain during 2020, genetic scrutiny of virus samples has unveiled signs of its persistence through Britain’s chilly winters, possibly via mosquitoes entering a dormant state, and also suggests fresh instances of the virus breaching UK borders post-2020.
Mr Folly acknowledged the complexity of the issue and urged the public to report any deceased blackbirds they find. “There’s no real cure, we can’t go out and catch blackbirds and vaccinate them, that’s a huge cost. Realistically, a lot of this is down to reporting diseased blackbirds in your garden,” he explained.
Additionally, Hanmer called on individuals to participate in the upcoming blackbird garden survey set for May.