Individual study: Taste aversion does not reduce food consumption in American kestrels Falco sparverius but dyeing food blue does
Nicholls M.K. (2000) An evaluation of methyl anthranilate, aminoacetophenone, and unfamiliar coloration as feeding repellents to American kestrels. J Raptor Res, 34, 311-318
This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.
Use repellents on baits for predator control
A replicated, randomised and controlled, ex situ experiment (Nicholls 2000) found that on three of four test days, 33 captive American kestrels Falco sparverius were no less likely to choose to consume chicks with feeding repellent (dead day-old chicks treated with either methyl anthanilate or aminoacetophenone) compared to untreated chicks. Kestrels fed on treated chicks consumed less over the study (with fewer methyl anthanilate-treated chicks consumed), but not to the point of losing body condition (body weights were similar across treatments). Treating chicks with repellents did not affect consumption in comparison to dyeing them blue or green (see ‘Use coloured baits to reduce accidental mortality during predator control’). This study is also discussed in ‘Use aversive conditioning to reduce nest predation’.
Use coloured baits to reduce accidental mortality during predator control
A replicated, randomised and controlled, ex situ experiment (Nicholls 2000) found that consumption of day-old chicks by 33 American kestrels Falco sparverius was greatly reduced by dying chicks green or blue, with no birds consuming blue-dyed chicks and two birds also avoiding green-dyed chicks. All birds reduced food intake significantly. Treating chicks with two repellents (discussed in ‘Use repellents on baits’) did not affect consumption in addition to dyeing. This study is also discussed in ‘Use aversive conditioning to reduce nest predation’.
Use aversive conditioning to reduce nest predation by avian predators
A replicated, randomised and controlled ex situ experiment with 33 American kestrels Falco sparverius (Nicholls 2000) found that control (untreated) day-old chicks were preferentially chosen, compared with chicks treated with methyl anthranilate on two out of four experimental days (ten birds choosing controls first vs. one choosing methyl anthranilate treated chicks and nine choosing controls vs. two choosing treated). Birds showed a preference for controls over aminoacetophenone-treated chicks on one day (nine choosing controls vs. two choosing treated chicks). On all other days there was no difference in preference for treatment or control chicks. The total amount of food consumed was highest for control kestrels, intermediate for those fed on aminoacetophenone-treated chicks and lowest for those fed methyl anthranilate-treated chicks, however, kestrels did not appear to lower consumption to the point of threatening body condition: there were no significant differences between kestrel weights at the end of the trial. A further replicated, randomised and controlled experiment found that treating cockerels with the two chemicals and dyeing them either green or blue greatly reduced food intake. However, there was no difference between consumption of dyed and treated chicks and controls that were only dyed, suggesting that aversive conditioning was not occurring. This study is also discussed in ‘Use coloured baits to reduce accidental mortality during predator control’ and ‘Use repellents on baits’.