The visual fields of two ground-foraging birds, House Finches and House Sparrows, allow for simultaneous foraging and anti-predator vigilance

Publication Type:Journal Article
Year of Publication:2008
Authors:Fernández-Juricic, E, Gall, MD, Dolan, T, TISDALE, VANESSA, Martin, GR
Journal:Ibis
Volume:150
Issue:4
Date Published:2008
ISBN Number:1474-919X
Keywords:binocular vision, Burrica, Burrica mexicana, Carpodacus, Carpodacus mexicanus, Fringillidae, Haemorhous, Haemorhous mexicanus, lateral vision, mutual exclusivity assumption, orbit orientation, Passer, Passer domesticus, Passeridae, predation risk, scanning
Abstract:In birds, differences in the extent and position of the binocular visual field reflect adaptations to varying foraging strategies, and the extent of the lateral portion of the field may reflect anti-predator strategies. The goal of this study was to describe and compare the visual fields of two ground-foraging passerines, House Finch Carpodacus mexicanus and House Sparrow Passer domesticus. We found that both species have a binocular field type that is associated with the accurate control of bill position when pecking. Both species have eye movements of relatively large amplitude, which can produce substantial variations in the configuration of the binocular fields. We propose that in these ground foragers, their relatively wide binocular fields could function to increase foraging efficiency by locating multiple rather than single food items prior to pecking events. The lateral fields of both species are wide enough to facilitate the detection of predators or conspecifics while head-down foraging. This suggests that foraging and scanning are not mutually exclusive activities in these species, as previously assumed. Furthermore, we found some slight, but significant, differences between species: House Sparrow binocular fields are both wider and vertically taller, and the blind area is wider than in House Finches. These differences may be related to variations in the degree of eye movements and position of the orbits in the skull.
URL:http://dx.doi.org/10.1111/j.1474-919X.2008.00860.x
Short Title:Ibis
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith