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La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	The penetrating gaze – new light on old ideas on mimicry and intimidating appearance. (2013)
Auteurs :	Bernd Leisler, Auteur ; Karl Schulze-Hagen, Auteur
Type de document :	Article
Dans :	Vogelwarte (51(1) 2013)
Article en page(s) :	55-62
Langues:	Allemand
Résumé :	The pale-coloured eyes of certain vertebrate species can give the impression of a ‘penetrating gaze’ and a threatening or dangerous appearance. However, there have been few tests of this hypothesis, but three recent studies of birds – in which pale irides are more common than in mammals – provide some intriguing ideas. First, in the Common Cuckoo, the effectiveness of its hawk mimicry is enhanced by the pale eyes. The pattern of yellow iris and dark pupil is particularly important in creating an alarm reaction in its host species (Welbergen & Davies 2011, 2012; Trnka et al. 2012). Second, the Barred Warbler, whose German name translates as Sparrowhawk Warbler and is characterized by a piercing yellow eye, often builds its nest close to that of Red-backed Shrikes (Glutz & Bauer 1991).. It was originally thought that this association favoured only the warblers, but a study by Golawksi (2007) indicates that shrikes with ‘attendant’ Barred Warblers enjoy greater breeding success than those without, possibly because of the Barred Warblers aggression. Third, the Collared Araçari (a toucan species) has pale eyes and a very large but weak bill which together gives the species an alarming appearance – literally – to those species whose nests they rob (Bühler 1997). Animals whose eyes have a light-coloured periphery and a black centre are generally regarded as a presenting an intimidating signal (Cott 1940, Scaife 1976 a, 1976b). In birds, pale irides (often enhanced by reduction in pupil size) generate a “penetrating gaze” by emphasizing the direction of the gaze. As well as – possibly – serving an intimidating or threatening function, pale-coloured eyes may also serve a sexual and social function by making their owners more conspicuous. We encourage researchers to test the hypothesis that pale-eyed individuals or species are regarded as more dominant by adversaries and hence have greater access to resources (e.g. sexual partners, food) than dark-eyed birds).

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