Balloons and kites are usually positioned so that they appear as hovering above the crops, thereby placing them above the targeted wildlife species, sometimes mimicking the looks and movements of flying raptors to add extra wariness.
A study from New Zealand implemented eye-spot balloons in vineyards to deter birds, including starlings (Sturnus vulgaris) damage to grapes (Fukuda et al. 2008). Although the researchers observed some reduction in the damage levels compared to the control, bird damage to grapes was still high in treatment blocks (RR = 0.91). Kandil and Mobarak (2017) implemented a balloon network at two Egyptian sites. In comparison to control farms, farms with the balloon network observed slightly reduced house sparrow (Passer domesticus) damage to rice in two subsequent years (RR = 0.59 and RR = 0.73). The effect was less pronounced for reducing laughing dove (Spilopelia senegalensis) damage to sorghum (RR = 0.85 and RR = 0.82). In Connecticut, USA, Conover (1984) evaluated the effect of a Haw-kite to prevent damage on corn ears and yields from red-winged blackbirds (Agelaius phoeniceus) and common grackles (Quiscalus quiscula). In comparison to control fields the damage yield was reduced in treatment field (RR = 0.17), and protected rows suffered lower damage to crop ears than unprotected rows (RR = 0.38). Hothem and DeHaven (1982) evaluated the effect of a raptor-mimicking kite suspended from a helium-filled balloon (kite-balloon or KB) could reduce bird damage to ripening wine grapes in California, USA. When the kite was in use, the damage to grapes was reduced in comparison to control periods during two subsequent years (RR = 0.66 and RR = 0.52). The authors experienced that birds became habituated to the kite which reduced the effect over time but suggest that habituation could be counteracted by regularly changing the KB components and deployment method. Seamans et al. (2002) evaluated the Allsopp Helikites® for their effectiveness to reduce gull (Larus spp.) damage on sunflowers and observed a slight reduction in the seed loss in treatment plots compared to controls (RR = 0.68).
