Mate choice in zebra finches: does corticosterone play a role?

The importance of stress as a factor in influencing life history strategies has received considerable attention in recent years, because it appears to have a substantial impact on an individual's behaviour and physiology. Birds respond to environmental and social stressors by the production of corticosterone, a glucocorticoid hormone released by the adrenal gland. In this experiment, we tested whether female zebra finches preferred males selected to produce low or high peak levels of circulating plasma corticosterone. Plasma corticosterone and testosterone levels of the males were recorded, as were morphometric measurements and perch activity. Spectrophotometric measurements were also taken from several putatively sexually selected regions of the males. The females preferred the males from the low corticosterone lines to the high corticosterone males. In addition to, and consistent with this effect, females preferred males with the lowest corticosterone titres. Male activity, testosterone level, body size and mass had no effect on female preference. Leg and beak brightness were important, however, as were the brightness and chromaticity of the male cheek patch. These results are discussed in relation to contemporary hypotheses in sexual selection, particularly in the context of stress-mediated signalling.

Ultraviolet colour perception in European starlings and Japanese quail

Whereas humans have three types of cone photoreceptor, birds have four types of single cones and, unlike humans, are sensitive to ultraviolet light (UV, 320-400 run). Most birds are thought to have either a violet-sensitive single cone that has some sensitivity to UV wavelengths (for example, many non-passerine species) or a single cone that has maximum sensitivity to UV (for example, oscine passerine. species). UV sensitivity is possible because, unlike humans, avian ocular media do not absorb UV light before it reaches the retina. The different single cone types and their sensitivity to UV light give birds the potential to discriminate reflectance spectra that look identical to humans. It is clear that birds use UV signals for a number of visual tasks, but there are few studies that directly demonstrate a role for UV in the detection of chromaticity differences (i.e. colour vision) as opposed to achromatic brightness. If the output of the violet/UV cone is used in achromatic visual tasks, objects reflecting more UV will appear brighter to the bird. 11, however, the output is used in a chromatic mechanism, birds will be able to discriminate spectral stimuli according to the amount of reflected light in the UV part of the spectrum relative to longer wavelengths. We have developed a UV 'colour blindness' test, which we have given to a passerine (European starling) and a non-passerine (Japanese quail) species. Both species learnt to discriminate between a longwave control of orange vs red stimuli and UV vs 'non-UV' stimuli, which were designed to be impossible to differentiate by achromatic mechanisms. We therefore conclude that the output of the violet/UV cone is involved in a chromatic colour vision system in these two species.

Knowledge on road information in sub-urban lane detection via multiple cue integration

Detection of lane boundaries of a road based on the images or video taken by a video capturing device in a suburban environment is a challenging task. In this paper, a novel lane detection algorithm is proposed without considering camera parameters; which robustly detects lane boundaries in real-time especially for sub-urban roads. Initially, the proposed method fits the CIE L*a*b* transformed road chromaticity values (that is a* and b* values) to a bi-variate Gaussian model followed by the classification of road area based on Mahalanobis distance. Secondly, the classified road area acts as an arbitrary shaped region of interest (AROI) in order to extract blobs resulting from the filtered image by a two dimensional Gabor filter. This is considered as the first cue of images. Thirdly, another cue of images was employed in order to obtain an entropy image. Moreover, results from the color based image cue and entropy image cue were integrated following an outlier removing process. Finally, the correct road lane points are fitted with Bezier splines which act as control points that can form arbitrary shapes. The algorithm was implemented and experiments were carried out on sub-urban roads. The results show the effectiveness of the algorithm in producing more accurate lane boundaries on curvatures and other objects on the road.

Study on the dyeing properties of hemicyanine dyes. I. Acrylic fabrics

Three hemicyanine dyes were employed in dyeing acrylic fabrics following traditional cationic dyeing procedures. The influence of the substituting groups of the dye molecule on the sorption rate and sorption isotherms was analyzed. The results showed that those dyed acrylic fabrics using hemicyanine dyes had obvious fluorescent effect in the spectra range 550–750 nm. In addition, according to the EN-471 standard (2003), the chromaticity of dyed acrylic fabric was calculated to evaluate whether hemicyanine dye could meet the requirements of the fluorescent dye for high visibility warning clothing.

Real-time lane detection on suburban streets using visual cue integration

The detection of lane boundaries on suburban streets using images obtained from video constitutes a challenging task. This is mainly due to the difficulties associated with estimating the complex geometric structure of lane boundaries, the quality of lane markings as a result of wear, occlusions by traffic, and shadows caused by road-side trees and structures. Most of the existing techniques for lane boundary detection employ a single visual cue and will only work under certain conditions and where there are clear lane markings. Also, better results are achieved when there are no other onroad objects present. This paper extends our previous work and discusses a novel lane boundary detection algorithm specifically addressing the abovementioned issues through the integration of two visual cues. The first visual cue is based on stripe-like features found on lane lines extracted using a two-dimensional symmetric Gabor filter. The second visual cue is based on a texture characteristic determined using the entropy measure of the predefined neighbourhood around a lane boundary line. The visual cues are then integrated using a rulebased classifier which incorporates a modified sequential covering algorithm to improve robustness. To separate lane boundary lines from other similar features, a road mask is generated using road chromaticity values estimated from CIE L*a*b* colour transformation. Extraneous points around lane boundary lines are then removed by an outlier removal procedure based on studentized residuals. The lane boundary lines are then modelled with Bezier spline curves. To validate the algorithm, extensive experimental evaluation was carried out on suburban streets and the results are presented. 

An integrative framework for the appraisal of coloration in nature

The world in color presents a dazzling dimension of phenotypic variation. Biological interest in this variation has burgeoned, due to both increased means for quantifying spectral information and heightened appreciation for how animals view the world differently than humans. Effective study of color traits is challenged by how to best quantify visual perception in nonhuman species. This requires consideration of at least visual physiology but ultimately also the neural processes underlying perception. Our knowledge of color perception is founded largely on the principles gained from human psychophysics that have proven generalizable based on comparative studies in select animal models. Appreciation of these principles, their empirical foundation, and the reasonable limits to their applicability is crucial to reaching informed conclusions in color research. In this article, we seek a common intellectual basis for the study of color in nature. We first discuss the key perceptual principles, namely, retinal photoreception, sensory channels, opponent processing, color constancy, and receptor noise. We then draw on this basis to inform an analytical framework driven by the research question in relation to identifiable viewers and visual tasks of interest. Consideration of the limits to perceptual inference guides two primary decisions: first, whether a sensory-based approach is necessary and justified and, second, whether the visual task refers to perceptual distance or discriminability. We outline informed approaches in each situation and discuss key challenges for future progress, focusing particularly on how animals perceive color. Given that animal behavior serves as both the basic unit of psychophysics and the ultimate driver of color ecology/evolution, behavioral data are critical to reconciling knowledge across the schools of color research.