U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version



Applied Animal Behaviour Science 159 (2014) 107–113.


U.S. government work.


Application strategies for avian repellents are needed to maintain efficacious repellentconcentrations throughout the period of needed crop protection. We investigated the repellency of an ultraviolet (UV) feeding cue in the absence of postingestive consequences, thecombination of the UV feeding cue and an UV-absorbent, postingestive repellent (i.e., arepellent that causes negative postingestive consequences), and a non-UV feeding cue com-bined with the UV-absorbent, postingestive repellent in red-winged blackbirds (Agelaiusphoeniceus). In the absence of negative postingestive consequences, 0.2% of the UV feed-ing cue (wt/wt) was not aversive relative to untreated food (i.e., baseline preference test; P = 0.1732). Relative to the repellency of food treated only with the anthraquinone-basedrepellent, synergistic repellency (i.e., 45–115% increase) was observed when 0.2% of the UVfeeding cue was combined with 0.02% or 0.035% anthraquinone (wt/wt). In contrast, <10%repellency was observed for 0.2% of a non-UV feeding cue (red #40 aluminum lake disper-sion) paired with 0.02% anthraquinone. Aversion performance was therefore not attributedto characteristics of either conditioned or unconditioned stimuli but their combinations,and enhanced repellency of anthraquinone plus the UV-absorbent cue was attributed toUV wavelengths. Thus, the addition of an UV feeding cue can enhance avian repellencyat repellent concentrations realized from previous field applications on agricultural crops(e.g., ≤1000 ppm anthraquinone).

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