The blackbird, which for over a decade was the most common bird in Flemish gardens, is becoming increasingly scarce due to the Usutu virus.
Between 2004 and 2017, blackbirds were spotted in 80% to 90% of gardens, according to figures from nature conservation association Natuurpunt. This year, however, they were seen in only 63% of gardens – a 4.9 percentage point drop from 2024 and nearly a third less than at the start of the counts in 2004.
The usutu virus is responsible for this decline. This relatively new disease originated in Africa and reached Europe via Tuscany (Italy) at the beginning of this century. It is transmitted by mosquitoes and primarily affects birds. In 2016, the virus caused a 15% decrease in the breeding population of blackbirds; in 2017, certain parts of Flanders saw a reduction of up to 50%.
House sparrows also showed the poorest numbers since the counts began. They were spotted in just 42.4% of gardens – 4.7 percentage points lower than in 2024 and almost a fifth less than in 2004. The primary cause for house sparrows is the loss of their specific habitats, such as wilder gardens and shrubbery. In absolute numbers, however, house sparrows still lead the top three, followed by blue tits and chaffinches.
Turkish turtle doves are also declining, likely due to the dominance of the larger wood pigeon. Conversely, jackdaws and goldfinches are thriving.
This year, 57,650 people participated in Natuurpunt’s Great Bird Weekend, during which a total of 887,728 birds were spotted.
