Effectiveness of the bird repellents anthraquinone and d-pulegone on an endemic New Zealand parrot, the kea (Nestor notabilis)

Abstract

The toxin 1080 (sodium fluoroacetate) is widely used to control introduced mammalian pests in New Zealand. By-kill of non-target native species, particularly birds, does occur including that of the endemic New Zealand parrot, the kea (Nestor notabilis). In large-scale control operations the toxin is normally presented within cereal-based pellets distributed by aerial application. This occurs after prefeeding with nontoxic cereal-based pellets, providing the opportunity for introducing bird-specific repellents to pellets to reduce by-kill. We tested the effectiveness of a combination of a secondary repellent, anthraquinone (Avipel®) (0.1%), and a primary repellent, d-pulegone (0.17%), in deterring consumption of cereal-based pellets by captive kea. Sample groups of one or two kea at five different captive facilities were presented with a sequence of both untreated and treated pellets over a 3-week study period. Birds were initially presented with pellets containing no repellents followed in sequence, at 3-day intervals, with pellets containing both repellents, the primary repellent only, and finally with no repellents again. There was a 69% decrease in the mass of pellets ingested, from a mean (±S.E.) of 9.8±2.9gbird−1day−1 (no repellent) to 3.0±1.2gbird−1day−1 (primary plus secondary repellent). When birds were then presented with pellets containing only the primary repellent, there was a further decrease in consumption to 1.1±0.2gbird−1day−1, an 88.7% reduction from initial consumption rates. Consumption of untreated pellets presented at the end of the trial then rose to 4.6±2.0gbird−1day−1, or 52.8% of initial rates. The repellent combination at the trialled concentrations was effective at repelling kea from ingesting cereal-based pellets, but continued use of the primary repellent was required to maintain the aversion response on subsequent exposure to pellets. Introduction of these repellents into toxin-laced pellets may reduce by-kill of kea and other non-target native birds during pest control operations.