The subtlety of simple eyes: the tuning of visual fields to perceptual challenges in birds

Birds show interspecific variation both in the size of the fields of individual eyes and in the ways that these fields are brought together to produce the total visual field. Variation is found in the dimensions of all main parameters: binocular region, cyclopean field and blind areas. There is a ph...

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Bibliographic Details
Published in:Philosophical transactions of the Royal Society of London. Series B. Biological sciences 2014-02, Vol.369 (1636), p.20130040-20130040
Main Author: Martin, Graham R.
Format: Article
Language:English
Subjects:
Animals
Binocular Vision
Birds
Birds - anatomy & histology
Birds - physiology
Eye - anatomy & histology
Feeding Behavior
Flight, Animal
Foraging
Optic Flow-Field
Review
Sensory Ecology
Visual Fields
Visual Fields - physiology
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Summary:Birds show interspecific variation both in the size of the fields of individual eyes and in the ways that these fields are brought together to produce the total visual field. Variation is found in the dimensions of all main parameters: binocular region, cyclopean field and blind areas. There is a phylogenetic signal with respect to maximum width of the binocular field in that passerine species have significantly broader field widths than non-passerines; broadest fields are found among crows (Corvidae). Among non-passerines, visual fields show considerable variation within families and even within some genera. It is argued that (i) the main drivers of differences in visual fields are associated with perceptual challenges that arise through different modes of foraging, and (ii) the primary function of binocularity in birds lies in the control of bill position rather than in the control of locomotion. The informational function of binocular vision does not lie in binocularity per se (two eyes receiving slightly different information simultaneously about the same objects from which higher-order depth information is extracted), but in the contralateral projection of the visual field of each eye. Contralateral projection ensures that each eye receives information from a symmetrically expanding optic flow-field from which direction of travel and time to contact targets can be extracted, particularly with respect to the control of bill position.
ISSN:0962-8436
1471-2970
DOI:10.1098/rstb.2013.0040