Date of Award
avian deterrents, veraison, vineyards
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There exists a strong co-evolutionary relationship between many fruit plants and the birds that act as seed dispersers. This relationship presents an issue to vineyards in the form of hungry birds foraging on their crops. In this thesis, I use an experimental approach to test the effectiveness of avian deterrents, quantify physical attributes of grapes as they mature, and quantify the impact that foraging birds have on grape crops. In my first data chapter, I record the directional movements of birds in vineyards in response to four avian deterrents (propane cannons, speakers broadcasting calls of avian predators, hawk kites, and drones) and a control. Of these four deterrents, only propane cannons and speakers broadcasting predator calls were effective at deterring birds. My findings highlight the importance of using multiple deterrents to increase the effectiveness of non-invasive bird control. In my second data chapter, I used grape samples to monitor the physical changes grapes experience as they mature, and assessed bird predation on grapes at vineyards. I concluded that red, green, and pink cultivars exhibited similar changes in size and sugar content, but that red gape cultivars experienced a more drastic colour change during veraison. Furthermore, I found that red grape cultivars experienced more removal and damage from birds than green or pink cultivars. Additionally, I found that sugar content was primarily predicted by RGB (red blue green) hue and brightness for red cultivars RGB hue and chroma for green cultivars, suggesting that birds could use grape colour as a signal of sugar and nutritional content, which may influence rates of grape predation by birds. Finally, this chapter revealed that netting is an effective barrier in reducing grape predation by birds. My research stresses the importance of understanding the development of grapes in order to predict when and where grape losses and damage are most likely to occur so that the correct avian deterrents can be applied for optimal protection.
Bastien, Grace Anne, "Avian grape predation at vineyards: Evaluating fruit preferences and non-invasive deterrent methods" (2021). Electronic Theses and Dissertations. 8547.