scholarly journals Mechanisms involved in the production of differently colored feathers in the structurally-colored Swallow Tanager (Tersina viridis; Aves: Thraupidae)

2020 ◽  
Author(s):  
Tomás Bazzano ◽  
Mendicino Lucas ◽  
Marina E. Inchaussandague ◽  
Diana C. Skigin ◽  
Natalia C. García ◽  
...  
Keyword(s):  
Reflectance Spectrum ◽  
Reflectance Spectra ◽  
Color Differences ◽  
Light Reflectance ◽  
Greenish Blue ◽  
Light Green ◽  
Morphology Changes ◽  
Reflectance Peak ◽  
Do So

ABSTRACTNon-iridescent, structurally-based coloration in birds originates from the feather’s internal nanostructure (the keratin spongy matrix), but the presence of melanin and the characteristics of the barb’s cortex can affect the resulting color. Here we investigate how this nanostructure is regulated and combined with other elements in differently-colored plumage patches. To do so, we investigated the association between light reflectance and the morphology of feathers from the back and belly plumage patches of male Swallow Tanagers (Tersina viridis), which look greenish-blue and white, respectively. Both plumage patches have a reflectance peak around 550 nm, but the reflectance spectrum is much less saturated in the belly. The barbs of both types of feathers have similar spongy matrices at their tips which produce similar reflectance spectra. However, the color of the belly feather barbs changes from light green at the tip to white closer to the rachis. These barbs lack pigments and their morphology changes considerably: the spongy matrix is reduced, being almost hollow, and has a different shape towards the rachis. Instead, we observed deposition of melanin underneath the spongy matrix in the back feathers which had a much saturated coloration that was consistent along the barbs’ length. Overall, our results suggest that the color differences between the white and greenish-blue plumage are mostly due to the differential deposition of melanin and a reduction of the spongy matrix in some parts of the belly feather barbs, and not a result of changes in the periodicity of the spongy matrix.

Laterally Graded Rugate Filters in Porous Silicon

2003 ◽  
Vol 797 ◽  
Author(s):  
Sean E. Foss ◽  
Terje G. Finstad
Keyword(s):  
Refractive Index ◽  
Porous Silicon ◽  
Near Infrared ◽  
Reflectance Spectrum ◽  
Voltage Drop ◽  
Optical Parameters ◽  
Filter Surface ◽  
Strong Reflection ◽  
Discrete Layer ◽  
Reflectance Peak

ABSTRACTRugate optical reflectance filters with position dependent reflectance peaks in the visible to near infrared spectrum were realized in porous silicon (PS). Filters with strong reflection peaks, near 100%, no detectable higher order harmonics and suppressed sidebands compared to discrete layer filters were obtained by varying the current density continuously and periodically during etching. An in-plane voltage up to 1.5 V was used to obtain refractive index and periodicity change along the filter surface resulting in reflectance peak shifts of up to 100 nm/mm in the direction of the voltage drop. The effect of the lateral change in optical parameters on the filter characteristics is studied by varying the gradient and comparing measurements at different positions with measurements on a non-graded filter. We have observed extra features in the reflectance spectrum of these graded filters compared with reflectance from a non-graded filter which is likely caused by the gradient.

scholarly journals Subspecific and Temporal Variation in the Structurally Based Coloration of the Ultramarine Grosbeak

The Condor ◽  
2007 ◽  
Vol 109 (1) ◽  
pp. 187-192 ◽  
Author(s):  
Ana S. Barreira ◽  
Dario A. Lijtmaer ◽  
Stephen C. Lougheed ◽  
Pablo L. Tubaro
Keyword(s):  
Temporal Variation ◽  
Gradual Increase ◽  
Color Variation ◽  
Reflectance Spectra ◽  
Plumage Coloration ◽  
Sexual Dichromatism ◽  
Ambient Light ◽  
Uv Reflectance ◽  
Color Differences ◽  
Dark Blue

Abstract Abstract Ultramarine Grosbeaks (Cyanocompsa brissonii) possess a striking sexual dichromatism, with males dark blue and females brown. There are two subspecies in Argentina: the larger-bodied C. b. argentina, which is common in shrubs and semiopen areas, and the smaller C. b. sterea that inhabits forests. We measured reflectance spectra of six plumage patches from study skins to evaluate the possibility of color differences between males of each subspecies and temporal variation in plumage coloration. We found differences between subspecies in color brightness, hue, saturation, and UV chroma in the plumage patches of more conspicuous coloration, which could be related to ambient light differences between the environments that each subspecies inhabits. We also documented temporal color variation in some plumage patches, in particular a gradual decrease of UV reflectance and a gradual increase in hue after molting, possibly attributable to feather wear.

Effects of colour bands on male competition and sexual attractiveness in zebra finches (Poephila guttata)

1987 ◽  
Vol 65 (2) ◽  
pp. 333-338 ◽  
Author(s):  
Laurene M. Ratcliffe ◽  
Peter T. Boag
Keyword(s):  
Reproductive Success ◽  
Activity Level ◽  
Sexual Attractiveness ◽  
Zebra Finches ◽  
Nest Boxes ◽  
Poephila Guttata ◽  
Male Activity ◽  
Light Green ◽  
Intermale Competition ◽  
Do So

Recent work suggests that coloured plastic leg bands may alter the sexual attractiveness and reproductive success of zebra finches (Poephila guttata). For example, males wearing red bands are more attractive to females and have enhanced reproductive success compared with males that have light green bands. Colour bands have been widely used in studies of avian behaviour and therefore could introduce bias if they regularly have a significant impact on social interactions among individuals. We carried out an experiment to assess the proximate effects of colour bands on zebra finch behaviour. Male zebra finches maintained in a large indoor aviary were given either red or light green bands and then scored for their ability to compete for a limited number of nest boxes and to attract females. The same males were randomly reassigned either red or light green bands and tested for their ability to regain boxes and attract new females. We found no correlation between band colour and a male's ability to gain either a nest or female. However, there was an association between male activity level and success. Also, those males that attracted a female in the first part of the experiment were more likely to do so in the second part of the experiment. We conclude that any immediate advantages conferred by attractive band colours may be masked under conditions of strong intermale competition for nests and mates.

Optical Properties of Random Multilayers of Amorphous A-Si:H/A-Si3N4+x:H and the Classical Localization

1991 ◽  
Vol 219 ◽  
Author(s):  
Shoji Nitta ◽  
Kohji Ogawa ◽  
Takehiro Furukawa ◽  
Takashi Itoh ◽  
Shuichi Nonomura
Keyword(s):  
Light Propagation ◽  
Reflectance Spectrum ◽  
Localization Length ◽  
The Other ◽  
Absorption Coefficients ◽  
Anomalous Peak ◽  
Classical Localization ◽  
Optical Reflectance Spectrum ◽  
Reflectance Peak ◽  
Average Layer Thickness

ABSTRACTIn the optical reflectance spectrum of the random multilayers of a-Si:H/a-Si3N4+x:H, it is observed an anomalous peak which is explained by the classical localization of light propagation. The following two subjects are discussed in this report; (a). The Kramers-Kronig transformation is done including the anomalous disorder-related reflectance peak. Extra absorption coefficients Δα are obtained by this analysis. Energy dependence of the localization length 1(hv) of light propagation are obtained by 1(hv)=1/Δα(hv). (b). The other is the experiment on scaling where the ratio of the disorder and the average layer thickness is kept constant but the size of each layer is changed in each experiment

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