Homeowners lucky enough to have blackbirds visiting their gardens are being encouraged to take vital action to help the survival of this species. Experts warn that the bird’s population is ‘dwindling’ due to the spread of a mosquito-borne virus, which has now reached as far west as Dorset from its initial detection in London.
The Usutu virus, first identified in South Africa, has been causing devastation to blackbird populations since it was first discovered in the UK five years ago. From its initial outbreak in Greater London, where blackbird numbers have plummeted by 40 per cent since 2018, the virus has firmly established itself across the southeast.
According to preliminary results from a garden survey conducted last year by the British Trust for Ornithology (BTO), the virus has now extended as far west as Portland Bill and east across East Anglia. While it has not yet reached the Midlands, experts see no reason why a northward spread won’t occur, as reported by The Times.
As of summer last year, blackbird numbers have declined by approximately 10 per cent in East Anglia and the southeast of England, and about 5 per cent in southwest England. Hugh Hanmer, a senior research ecologist at the BTO, has suggested several strategies that gardeners can implement to support blackbirds.
He highlighted the importance of being vigilant about potential mosquito breeding grounds, such as open water butts, in response to 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 said.
The increasing threat posed by climate change exacerbates the problem by fostering conditions that allow these viruses to thrive. In his study on the effect of well-maintained gardens on London’s blackbird population, Hanmer found gardens with mature greenery and ponds fared better than those with less vegetation.
Despite initial concerns, it appears ponds are not especially attractive to mosquitoes. “Ponds are useful. We don’t want people to get rid of their pond,” Hanmer advised.
Current research indicates a potential sharp decline in UK blackbird numbers, possibly by up to 40 per cent. Nevertheless, there’s hope that some blackbirds may develop a genetic resistance to offset this decline.
The UK’s enduring passion for feeding garden birds has resulted in a significantly larger population of these winged creatures compared to other European countries. With around 5 million breeding pairs of blackbirds across the country, any decline in their numbers could have considerable consequences.
Hanmer, an authority in the field, issued a warning: “We’re not going to lose blackbirds, but we could have a lot fewer of them.”
He stressed the urgency of the situation, highlighting that the virus currently impacting our feathered friends is just one among many pathogens threatening UK species. He also highlighted the vital role blackbirds play in controlling pests such as slugs.
The BTO previously stated: “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 downturn has been linked with the emergence of the Usutu virus, a new mosquito-borne disease in the UK that often proves fatal to blackbirds. First identified in London in the summer of 2020, it appears to have started spreading further into southern Britain. The virus is widespread on the near-Continent, and its spread has been associated with climate change, which has favoured the mosquitoes responsible for transmitting the virus.”
Despite similarities to the West Nile virus, which poses significant health risks to humans, Arran Folly from the UK’s Animal and Plant Health Agency has assured that the Usutu virus carries a “very low” risk to people in Britain, with no recorded cases of human infection in the country. Folly and his team are vigilantly tracking the virus’s spread by capturing up to 30,000 mosquitoes annually and working with bird ringers to monitor birds for signs of the virus and antibodies resulting from mosquito bites.
Since the Usutu virus was first detected in the UK in 2020, genetic analysis has shown that it can survive the cold British winters, possibly because mosquitoes enter a dormant phase, and there is evidence of new introductions of the virus into the UK post-2020. Mr Folly acknowledged the challenges in managing the situation and has urged the public to assist by reporting any dead 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.
Furthermore, Hanmer has called on people to participate in the upcoming blackbird garden survey set for May.