Between October and January of every year, millions of birds from central and northern Europe make their way south to the Mediterranean to spend their winter months in warmer conditions. But for hundreds of thousands of birds, it could be their final resting place.

That’s because high-intensive automated harvesting machinery meant to strip trees of their olives during the night are unintentionally sucking up songbirds with them, according to an editorial piece written in Nature. Olives are harvested at night to help preserve their “aromatic compounds”, but roosting birds blinded by bright lights and stunned by machinery become accidental victims in the process.

The Andalusian government in Spain has already put a halt to the process after it was found that 2.6 million birds were vacuumed every year, but other parts of Spain and other countries, including Portugal, still practice automated olive harvesting – something conservation groups are hoping to bring awareness to. It’s expected that around 96,000 birds die in Portugal every year due to nighttime olive harvesting.

According to Portuguese newspaper Expresso, at last count, almost 500 birds were killed in December and January after the Institute for Nature Conservation and Forests (ICNF) inspected 25 loads of olives harvested and found “an average of 6.4 dead birds per hectare.” In the 15,000 hectares (37,000 acres) of existing olive groves, it is estimated that almost 100,000 birds may be killed every year. Officials note that the numbers "are not statistically relevant to determine already the prohibition of the nocturnal picking,” reports the publication, adding that "it is necessary to strengthen the sampling in the next harvest season, between October and January" and only then "more drastic measures can be taken."

Image showing five carcasses of protected species on the nighttime collection trailer in November 2017. Council of Environment, Spain

However, the Portuguese Society for the Study of Birds (SPEA) is calling for a stop to nighttime harvests.

"The Birds Directive says that they should not be subject to disturbance in the rest period," said SPEA ornithologist Domingos Leitão. "If the birds of one row of birds are frightened they fly to another."

"When negative impacts like these are detected, the authorities must act swiftly and accordingly. We are talking about hundreds of thousands of dead birds," said Nuno Sequeira, head of Portuguese environmental organization Quercus. “The lack of regulation allows birds to die and other environmental impacts, such as soil erosion and contamination and pollution of aquifers with synthetic chemicals used in intensive and super intensive agriculture.”

A report conducted by the Council of Andalusia, which looked at intensive olive-harvesting practices, found that nesting birds are particularly vulnerable to environmental variables because they are asleep and unaware of what is happening. Furthermore, spotlights used during harvest blinds the birds.

More than a dozen species of birds were observed in the olive collection baskets, including black-headed warblers and robins. Banding of birds indicates that most come from France, Holland, Belgium, Germany, and Scandinavia as well as the United Kingdom and Baltic countries.

[H/T: Expresso and Bird Guides]