Flags and ribbons are primarily a visual deterrent that can reflect light, or move unpredictably in the wind, making its presence disturbing to wildlife.
Multiple studies from India have evaluated reflective ribbons and additional visual deterrents. One study implemented reflective ribbons to prevent bird damage on guava and found some reduction in the risk of damage on developing fruit during the rainy season (RR = 0.54). The effect of the reflective ribbons was minimal to reduce damage on ripening fruit during the rainy season (RR = 0.89), as well as developing (RR = 0.85) and ripening fruit (RR = 0.86) during the winter season (Arora et al. 2023). Reflective ribbons also somewhat reduced the risk of house crow (Corvus splendens) damage on maize (RR = 0.59) and rose-ringed parakeet (Psittacula krameri) and house crow damage on pea pods (RR = 0.08) in a protected field compared to a control field (Kler 2001a; Kler 2001b). In another study Kler and Singh (2006) found that the reflective ribbons somewhat reduced the risk of damage from rose-ringed parakeet, streaked fantail warbler (Cisticola juncidis), and plain wren-warbler (Prinia subflava) on Brassica varieties Gobhi sarson hyaola (RR = 0.58 – 0.64) and Gobhi sarson hybrid (RR = 0.43 – 0.59) in comparison to control plots. The study also attempted an evaluation of reflective ribbons on Indian mustard raya but this trial did not render any results as no damage occurred neither in the treatment or the control plots (Kler and Singh 2006). Patyal and Rana (2003) observed reduced levels of grape damage caused by bird in plants protected by bird scaring reflective ribbons, M/S Mars Packaging Ltd. (RR = 0.31). Dar and Vashishat (2022) evaluated the effect of reflective ribbons, in this study to reduce damage of rose-ringed parakeets (Psittacula krameri Scopoli) on sunflowers on two sites. The study found the intervention to reduce the risk of damage (RR = 0.45, RR = 0.38). They also evaluated the effectiveness of plates and CDs to reduce parakeet damage on sunflowers, but the damage reduction was less pronounced when implementing these interventions (plates RR = 0.69 and RR = 0.68, CDs RR = 0.76 and 0.79).
Visual deterrents have also been employed in other geographical locations. Different types of stripes were evaluated for preventing bird damage at two sites in Egypt (Kandil and Mobarak 2017). On the first site, house sparrow (Passer domesticus) damage on rice was assessed during two subsequent years. In comparison to control farms, a reduced risk of damage was observed on farms utilising metallic coloured stripes (RR = 0.28), and aluminium reflective stripes (RR = 0.11 in year 1, RR = 0.38 in year 2), but to a lesser extent when ornamental stripes were used (RR = 0.75). On the second site, laughing dove (Spilopelia senegalensis) damage to sorghum was reduced on farms utilising aluminium reflective stripes (RR = 0.15 in year 1, RR = 0.08 in year 2) and to a lesser extent ornamental stripes (RR = 0.40 in year 1, RR = 0.32 in year 2) in comparison to control farms.
Mason et al. (1993) evaluated the effect of placing white plastic flags at a density of 1 flag/acre to prevent snow goose (Chen caerulescens atlantica) damage on rye and wheat, and found that the crop were 42 % taller in treatment fields than in unprotected controls. White flags did however not impact the abundance of mute swans (Cygnus olor) in oil-rape seed fields in the UK (RR = 1.0), nor did the appliance of hazards warning tape with twine (RR = 1.97) over the entire study period although the researchers indicate there may be further investigation to be made for shorter time intervals (McKay and Parrott 2010). Summers and Hillman (1990) placed 20mm wide red fluorescent tape on 2,4m poles to deter brent geese (Branta bernicla) in the UK. The intervention caused a 100% reduction in goose presence on treatment fields and a reduction in damage on winter wheat was achieved on the treatment fields when there were untaped fields available. When there were no untaped fields available, the geese would graze in the taped fields but at lower intensity (Summers and Hillman 1990).
Only one study focused on deterring mammals with visual deterrents: Raharimihaja et al. 2016 evaluated the effect of coloured plastic flags (1m x 0,5m) to reduce damage from Pteropodid bats on lychee fruit in Madagascar and found a lower risk of damage (RR = 0.52) and a 95% reduction in damaged fruit respectively, when the intervention was implemented in their two study sites.
