Providing perches for predatory and aggressive birds appears to reduce the negative impact of frugivorous birds in vineyards

Abstract

Context: Birds active in vineyards in south-eastern Australia can reduce or enhance crop yields via their foraging activities (e.g. by consuming grapes or by preying on grape-eating species). Aims: We examined the effectiveness of artificial perches in encouraging predatory birds into vineyards to scare frugivorous birds and consequently reduce the damage they cause to grapes. Methods: We monitored 12 artificial perches for 4 months during the growing season, spread over six vineyards in north-eastern Victoria, and compared bird damage to grapes at these sites with control sites without perches. Key results: We found that raptors did not use the artificial perches. However, the large and aggressive Australian magpie (Cracticus tibicen) commonly used perches and we recorded 38 513 perch visits by this species. Grapevines around perch sites suffered >50% less grape damage (4.13% damage per bunch) than control sites (8.57% damage per bunch). Conclusions: Our results suggest that providing artificial perches in vineyards can play a role in reducing frugivore damage to grapes. However, the effectiveness of perches can vary under different environmental conditions and certain perch types are not suitable for all predatory or aggressive birds. Implications: Future research should focus on the potential role of large-bodied and competitively aggressive species such as the Australian magpie in altering the activity of smaller frugivorous birds in vineyards, and also on the optimum height and location of artificial perches within vineyards to increase visitation by other predatory or aggressive bird species.