Assessing kea perception of cereal baits using modelling of spectral reflectance

Kea (Nestor notabilis) are highly inquisitive parrots endemic to Aotearoa/New Zealand that often interact with novel items in their environment. To help reduce the risk of by-kill of kea during aerial 1080 pest-control operations, we investigated how kea perceive the different types of cereal baits typically used in such pest control. We measured the spectral reflectance of a range of baits including baits that incorporated different levels of a bird-repellent (anthraquinone) or a UV-reflecting biomarker (pyranine, used in conservation to determine whether a bird has interacted with bait), non-toxic prefeed baits, and green-dyed, toxic bait. In the absence of information about kea vision, we constructed a model of parrot vision by averaging spectral sensitivities of three parrot species. We found that kea are unlikely to visually distinguish between two baits that contain different concentrations of bird-repellent when they are dyed similarly (both green-dyed or both undyed). Additionally, kea are likely to visually distinguish between green-dyed and undyed baits, and baits with or without the biomarker pyranine. Our findings support the addition of bird repellent to pre-feed baits intended to establish learned avoidance behaviour. However, the addition of pyranine might inadvertently influence kea perception and interactions with bait. This research highlights the importance of considering the visual perception of a vulnerable non-target species to reduce risk during pest control efforts.