title: The intensity threshold of colour vision in a passerine bird, the blue tit (Cyanistes caeruleus).
abstract: Many vertebrates use colour vision for vital behaviour but their visual performance in dim light is largely unknown. The light intensity threshold of colour vision is known only for humans, horses and two parrot species. Here, we first explore this threshold in a passerine bird, the blue tit (Cyanistes caeruleus). Using classic conditioning of colour cues to food rewards in three individuals, we find a threshold ranging from 0.05 to 0.2 cd m(-2). Results are comparable to the two previously tested bird species. For tits, nest light conditions probably exceed that threshold, at least after sunrise. These results shed new light on the lively debate questioning the visual performance of cavity nesters and the evolutionary significance of egg and chick coloration. Although this needs further investigation, it is possible that blue tits exploit both colour and brightness cues when viewing their eggs, chicks or conspecifics in their nests.
authors.affiliation: UMR 7179 CNRS MNHN, 91800 Brunoy, France UMR 5175, CNRS CEFE, 34090 Montpellier, France dgomez@mnhn.fr.
authors.forename: Doris
authors.initials: D
authors.lastname: Gomez
authors.affiliation: UMR 5175, CNRS CEFE, 34090 Montpellier, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Grégoire
authors.affiliation: UMR 5175, CNRS CEFE, 34090 Montpellier, France.
authors.forename: Maria
authors.initials: M
authors.lastname: Del Rey Granado
authors.affiliation: UMR 5175, CNRS CEFE, 34090 Montpellier, France.
authors.forename: Marine
authors.initials: M
authors.lastname: Bassoul
authors.affiliation: UMR 5175, CNRS CEFE, 34090 Montpellier, France.
authors.forename: David
authors.initials: D
authors.lastname: Degueldre
authors.affiliation: UMR 5175, CNRS CEFE, 34090 Montpellier, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Perret
authors.affiliation: UMR 5175, CNRS CEFE, 34090 Montpellier, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Doutrelant
mesh_terms: D000818:Animals; D005075:Biological Evolution; D003116:Color; D055253:Color Vision / Q000502:physiology*; D003214:Conditioning, Classical; D008027:Light; D046109:Passeriformes / Q000502:physiology*; D010775:Photic Stimulation; D010858:Pigmentation / Q000502:physiology; D012201:Reward; D012684:Sensory Thresholds / Q000502:physiology*
keywords: Bird coloration; Cavity-nesting bird; Colour vision; Communication; Conditioning experiment; Egg coloration