Oblique color vision in an open-habitat bird: spectral sensitivity, photoreceptor distribution and behavioral implications

Abstract

SUMMARYColor vision is not uniform across the retina because of differences in photoreceptor density and distribution. Retinal areas with a high density of cone photoreceptors may overlap with those with a high density of ganglion cells, increasing hue discrimination. However, there are some exceptions to this cell distribution pattern, particularly in species with horizontal visual streaks (bands of high ganglion cell density across the retina) that live in open habitats. We studied the spectral sensitivity and distribution of cone photoreceptors involved in chromatic and achromatic vision in the Canada goose (Branta canadiensis), which possesses an oblique rather than horizontal visual streak at the ganglion cell layer. Using microspectrophotometry, we found that the Canada goose has a violet-sensitive visual system with four visual pigments with absorbance peaks at 409, 458, 509 and 580nm. The density of most cones involved in chromatic and achromatic vision peaked along a band across the retina that matched the oblique orientation of the visual streak. With the information on visual sensitivity, we calculated chromatic and achromatic contrasts of different goose plumage regions. The regions with the highest visual saliency (cheek, crown, neck and upper tail coverts) were the ones involved in visual displays to maintain flock cohesion. The Canada goose oblique visual streak is the retinal center for chromatic and achromatic vision, allowing individuals to sample the sky and the ground simultaneously or the horizon depending on head position. Overall, our results show that the Canada goose visual system has features that make it rather different from that of other vertebrates living in open habitats.

The effects of radar on avian behavior: Implications for wildlife management at airports

“…Chromatic contrast was calculated using the following parameters: (1) spectral properties of ambient light (irradiance), (2) reflectance of the white millet and sand substrates, and (3) sensitivity of the cowbird visual system. We used a StellarNet Black Comet portable spectroradiometer (StellarNet, Tampa, FL) to measure both irradiance and reflectance, as in Moore et al (2012).…”

Ultraviolet vision in lacertid lizards: evidence from retinal structure, eye transmittance, SWS1 visual pigment genes, and behaviour

“…We used brightfield microscopy techniques to identify the different oil droplet types present in lacertid eyes. Fluorescence microscopy was also used in order to identify oil droplets that selectively transmit or absorb UV wavelengths (Ohtsuka, 1984;Wilkie et al, 1998;Kram et al, 2010;Coyle et al, 2012;Moore et al, 2012). In addition, we used coloured filters for brightfield microscopy to determine the wavelength range encompassing the cut-off wavelength (i.e.…”

Do American Goldfinches See Their World Like Passive Prey Foragers? A Study on Visual Fields, Retinal Topography, and Sensitivity of Photoreceptors

“…Using the linear equation (absorbance = intercept + slope × wavelength) from the trend line, we calculated λ cut by setting the absorbance to a value of one. Because λ 0 is a property of an oil droplet transmittance and not its absorbance, we calculated λ 0 mathematically as in Moore et al [2012]. We graphed the absorbance curves of each visual pigment and oil droplet type by averaging the nonnormalized raw absorbance spectra within each visual pigment and oil droplet type.…”

“…We also predicted that the distribution of cone photoreceptors would match that of the retinal ganglion cells [e.g. Querubin et al, 2009;Moore et al, 2012], being higher around the fovea than in the retinal periphery, although little is known about cell density covariations at these two retinal layers in Passeriformes.…”