Europe has an estimated 421 million fewer birds today than it did 30 years ago, a study has found.
Around 90% of the losses have affected the most common and widespread species, including sparrows, skylarks, grey partridges and starlings.
Scientists believe the population crash can be linked to modern farming methods and deteriorating and fragmenting habitats.
Dr Richard Inger, one of the researchers from the University of Exeter, said: “It is very worrying that the most common species of bird are declining rapidly because it is this group of birds that people benefit from the most.
“It is becoming increasingly clear that interaction with the natural world and wildlife is central to human well-being, and significant loss of common birds could be quite detrimental to human society.”