Host Plant and Habitat Measurements
Background color, texture, complexity, and lighting can impact the perception of visual signals (Endler 1993). To account for the influence of background on artificial prey detection and/or perception, I measured two main habitat characteristics: canopy openness and plant size. I anticipated that more open canopies would increase avian attack rates (Blake & Hoppes 1986; Richards & Coley 2008), possibly by providing better lighting conditions for prey detection. In terms of plant size, I expected that individual prey items would be easier to find on smaller plants, also increasing avian attacks. Plant height measurements were taken (in cm) from ground-level at the base of the stem to the tip of the uppermost leaf. Plants used in the experiment were an average of 124.9cm tall (sd: 60.1cm). I measured canopy openness by taking upward digital photos with a 180° hemispheric lens at plant height directly above each plant, with the camera held level with the ground. I then processed these photos using ImageJ (version 1.53) to calculate the proportion of open sky relative to vegetative cover in each image.