The magpie and the grapes: increasing ozone exposure impacts fruit consumption by a common corvid in a suburban environment.

Abstract

The Eurasian magpie Pica pica is a resident bird species able to colonize farmlands and anthropized environments. This corvid shows a wide trophic spectrum by including fruits, invertebrates, small vertebrates, and carcasses in its diet. A camera-trap experiment has been carried out to test the effect of different ozone (O3 ) concentrations on potted Vitis vinifera plants, which result in different grape consumption rates by suburban birds. The test was performed at an Ozone-Free Air Controlled Exposure (FACE) facility, consisting of nine plots with three O3 levels where AA is ambient O3 concentration and two elevated O3 levels (ambient air with a 50% increase in O3 concentration, 1.5x AA; and ambient air with a 100% increase in O3 concentration, 2.0x AA). Camera-traps were located in front of each treatment area and kept active for 24 h/day and for 5-day periods throughout a total of 3 months to monitor grape consumption by birds. We collected a total of 38 videos: Eurasian magpies were the only grape consumers, with a total of 6.7 ± 3.3 passages per hour (mean ± SD), with no differences across different O3 treatments. The grapes in the AA treatment were consumed significantly faster than those in the 1.5x AA treatment, which were, in turn, consumed faster than those in the 2.0x AA treatment. After 3 days from the start of treatment, 94, 53 and 22% berries from AA, 1.5x AA, and 2.0x AA treatments were eaten, respectively. When the O3 was turned off, berries were consumed at the same rate among treatments. Increasing O3 concentrations limited grape consumption by the magpie likely because O3 acted as a deterrent for magpies, while the lower sugar content recorded in the 2.0x AA berries did not affect the consumption when O3 was turned off. Our results provided valuable insights to mitigate human-wildlife conflicts in suburban environments. This article is protected by copyright. All rights reserved.