Grey squirrels and wild cats are "devastating" Britain's songbird population, a study suggests.
Predatory animals are having as much an impact as modern farming practices, the report, commissioned by charity Songbird Survival, indicates.
When combined with the impact of predatory birds like sparrowhawks, this means up to 85% of adult songbirds are lost - with 100% of nests targeted.
Conservationists fear the number of predators is spiralling out of control.
This could have a significant long-term impact on songbird numbers throughout the UK, they say.
The study brings together previously unpublished research conducted at farms across Britain.
It suggests the major predators, grey squirrels and wild cats, are responsible for a sharp decline in farm birds.