Aposematic species exploit the ability of predators to associate, for example, conspicuous colouration with the unprofitability of prey. We tested the importance of colour for avoidance learning, memory and generalisation in wild-caught great tits (Parus major). First, we determined the birds’ initial colour preferences for red, yellow, orange and grey artificial prey items. The birds showed some preferences, as they were more willing to eat grey prey as their first choice, but these were not strong preferences. We then trained birds to discriminate red, yellow or variable (red and yellow) signals from grey where colours signalled palatable and unpalatable food. In general, the birds learned the discrimination task equally well, irrespective of which colours signalled unpalatability, and subsequently remembered the distinction between previously palatable and previously unpalatable colours in the memorability test. We did not find strong evidence that variability in the signal affected learning or memory. Our results suggest that, in a task where birds must discriminate between palatable and unpalatable prey, it does not matter which specific colour signals unpalatability, although this might be context-dependent. To study whether training also affects responses to unconditioned stimuli, we included orange prey items in the memorability test. Although orange had been palatable in the initial preference test, the birds ate fewer orange prey items after they had been trained to avoid red, yellow or both colours (variable signal) as unpalatable prey, but did not change their preference when trained that these colourful signals were palatable. This indicates that generalisation occurred more readily after a negative experience than a positive experience, a situation that would potentially allow imperfect mimicry to occur.
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We would like to thank Dr. Daniel Osorio for help with the designing of prey, Helinä Nisu for taking care of the birds and all of the staff at Konnevesi Research Station for assistance. Dr. Candy Rowe and an anonymous reviewer gave valuable comments to improve the manuscript. The study was funded by the Academy of Finland (Centre of Excellence in research and various academy projects), a Biotechnology and Biological Sciences Research Council studentship (A. D. Ham) and a Marie Curie grant (A. D. Ham). All experiments comply with the laws of Finland.
Alatalo RV, Mappes J (1996) Tracking the evolution of warning signals. Nature 382:708–710CrossRefGoogle Scholar
Bates HW (1862) Contributions to an insect fauna of the Amazon valley (Lepidoptera:Heliconidae). Trans Linn Soc Lond XXIII:495–556Google Scholar
Bateson M, Healy SD, Hurley TA (2003) Context-dependent foraging decisions in rufous hummingbirds. Proc R Soc Lond B Biol Sci 270:1271–1276CrossRefGoogle Scholar
Beatty CD, Beirinckx K, Sherratt TN (2004) The evolution of Müllerian mimicry in multispecies communities. Nature 431:63–67CrossRefPubMedGoogle Scholar
Cott HB (1940) Adaptive coloration in animals. Menthuen, LondonGoogle Scholar
Duncan CJ, Sheppard PM (1965) Sensory discrimination and its role in the evolution of Batesian mimicry. Behaviour 24:269–282CrossRefGoogle Scholar
Evans DL, Waldbauer GP (1982) Behavior of adult and naive birds when presented with a bumblebee and its mimic. Zeit fur Tierpsychol 59:247–259Google Scholar
Exnerová A, Landová E, Štys P, Fuchus R, Prokopá M, Cehláriková P (2003) Reactions of passerine birds to aposematic and non-aposematic firebugs (Pyrrhocoris apterus; Heteroptera). Biol J Linn Soc 78:517–525CrossRefGoogle Scholar
Fisher RA (1930) Genetical theory of natural selection. Clarendon, OxfordGoogle Scholar
Gagliardo A, Guilford T (1993) Why do warningly-coloured prey live gregariously? Proc R Soc Lond B Biol Sci 251:69–74CrossRefGoogle Scholar
Gamberale-Stille G (2001) Benefit by contrast: an experiment with live aposematic prey. Behav Ecol 12:768–772CrossRefGoogle Scholar
Gamberale-Stille G, Guilford T (2003) Contrast versus colour in aposematic signals. Anim Behav 65:1021–1026CrossRefGoogle Scholar
Gamberale-Stille G, Tullberg BS (1999) Experienced chicks show biased avoidance of stronger signals: an experiment with natural colour variation in live aposematic prey. Evol Ecol 13:579–589CrossRefGoogle Scholar
Gamberale-Stille G, Tullberg BS (2001) Fruit or aposematic insect? Context-dependent colour preferences in domestic chicks. Proc R Soc Lond B Biol Sci 268:2525–2529Google Scholar