Vertebrate damage to Azorean vineyards: the role of the endemic Azores Woodpigeon Columba palumbus azorica.

ABSTRACT

In the Azores, complaints about grape loss to birds have become recurrent. Although winegrowers frequently blame the endemic Azores Woodpigeon Columba palumbus azorica, data about the magnitude of grape damage and the species responsible for them are lacking. This study provides detailed information about grape damage caused by vertebrates on Pico Island, home to the main wine-growing area of the region. Vineyards were monitored during the ripening period in 2017 and 2018. Damage was assessed by determining the number of plucked, pecked and bitten grapes for a total of 850 bunches. Camera traps were placed in 113 enclosures providing detection and consumption rates of vertebrate species. GLM analysis was performed to test the effect of grape variety, distance to the woods, year and time before harvest on grape damage and consumption events. Damage was estimated at 10.3% (± 0.9) in 2017 and 8.7% (± 0.9) in 2018 and mostly consisted of plucked grapes. Ten vertebrate species were detected consuming grapes. Overall, 524 consumption events were registered. The Madeira lizard Teira dugesii, the Azores Blackbird Turdus merula azorensis and rodents (rats Rattus sp. and the house mouse Mus musculus) were responsible for most of those events. The Azores Woodpigeon accounted for three consumption events. GLM analysis showed that damage was greater in vines adjacent to woods and lower in traditional white varieties. This study constitutes an important baseline for the implementation of efficient measures to mitigate grape predation and sheds light on the minor role of the Azores Woodpigeon in grape damage.