Hundreds of thousands of legally-protected birds are killed in southern Europe every year after being sucked out of trees and into machines which are harvesting olives.

During the winter months from October to January, millions of birds from northern Europe, including the UK, flock to Mediterranean countries to escape the cold weather.

It is thought around 96,000 birds die every year in Portugal alone as a result of harvesting for olive oil production during the night-time.

France and Italy also carry out the practice, but specific numbers are not known.

Image: Around 96,000 birds die every year in Portugal as a result of olive harvesting

The Andalusian government in Spain, where an estimated 2.6 million birds used to be vacuumed up annually, has now stopped the practice.


Other big olive-producing countries should follow their lead, say researchers.

The problem of birds being vacuumed from the bushes is on a "catastrophic scale", according to the findings reported in the journal Nature.

Birds such as robins, goldfinches, greenfinches, warblers and wagtails are among those that suffer the biggest casualties.

It is believed there are around 100 dead birds in each harvest trailer during a night-time operation.

The trees are stripped of the fruits at night because cooler temperatures help to preserve the olives' aromatic flavours.

But in the dark there is less chance of the birds spotting the machines because they are sleeping.

However, if the harvesting happened during the day they could see them and then escape.

Martin Harper from the RSPB told Sky News: "We do know that sustainably managed olive grows are not only possible but very beneficial to wildlife and we need to encourage those."

He added: "More generally across Europe we know there are 421 million fewer birds today than there were 30 years.

"Agriculture is the biggest driver of change which is why the Common Agriculture Policy needs to be reformed to ensure public money supports farmers to provide space for nature on their farms."