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Plumage Patches (plumage + patch)
Selected AbstractsSexual dimorphism and dichromatism in Steere's Liocichla (Liocichla steerii)JOURNAL OF FIELD ORNITHOLOGY, Issue 4 2006Herman L. Mays Jr ABSTRACT Although sexual differences in birds can be extreme, differences between males and females in body size and plumage color are more subtle in many species. We used a genetic-based approach to determine the sex of male and female Steere's Liocichla (Liocichla steerii) and examine the degree of size dimorphism and plumage dichromatism in this apparently monomorphic species. We found that males were significantly larger than females. In addition, Steere's Liocichla have a prominent yellow plumage patch on the lores that was significantly larger in males than females for both live birds and museum specimens. We also used reflectance spectrometry to quantify the color of the yellow-green breast feathers of Steere's Liocichla and found no significant differences between males and females in brightness, intensity, saturation, or hue. However, females tended to have brighter breast plumage, particularly at long wavelengths. Collectively, these color variables were useful in discriminating birds according to sex when used in a discriminant function analysis. Our study suggests that sexual selection may be more widespread than once assumed, even among birds considered monomorphic, and emphasizes the need for additional data from tropical and subtropical species. SINOPSIS Aunque las diferencias sexuales entre algunas especies puede ser estrechas, un muchas de estas las diferencias corporales entre los sexos pudiera ser sutiles. Abordamos el asunto basados en genética para determinar el sexo en Liocichla steerii y examinamos el grado de dimorfismo sexual y dicromatismo en el plumaje en esta especie la cual aparentemente es monomórfica. Encontramos que los machos eran significativamente de mayor tamaño que las hembras. Además encontramos en los machos un parcho amarillo en los lores significativamente más grande que en las hembras, tanto en aves del estado silvestre como en pieles de museos. Usamos espectrometría para cuantificar el color de las plumas verde-amarillentas del pecho de las aves y no encontramos diferencias significativas entre los sexos, con respecto a la brillantez, insensidad, saturación o matiz color. Sin embargo, las hembras tuvieron la tendencia a tener el plumaje más brillante en el pecho particularmente en el espectro de onda larga. Colectivamente, estas variables de color fueron útiles para discriminar entre el sexo de las aves, particularmente cuando fueron examinadas utilizando un análisis discriminante de funciones. Nuestro estudio sugiere que la selección sexual pudiera estar más ampliamente distribuida que lo previamente asumido, aún en aves consideradas monomórficas. Además el trabajo enfatiza la necesidad de llevar a cabo estudios adicionales, de este tipo, tanto en especies del trópico como de la zona templada. [source] On silver wings: a fragile structural mechanism increases plumage conspicuousnessJOURNAL OF AVIAN BIOLOGY, Issue 5 2009Ismael Galván We report for the first time the existence of a structural mechanism of feathers different from iridescence that makes plumage conspicuous. By using electron and light microscopy, we show that the mechanism consists of special lengthened and twisted distal barbules that are very susceptible to damage. The dorsal side of these barbules is translucent, which creates a distinctive sheen colouration to feathers that otherwise would be dark. When distal sheen barbules are broken, the black proximal barbules are exposed, thus generating a conspicuous difference between abraded and non-abraded areas. Total and ultraviolet reflectance of sheen (non-abraded) areas are strikingly higher than in abraded areas. We propose that this mechanism represents a case of convergent evolution in species that are limited in developing colourful plumage patches. Future studies should explore the potential of this colour mechanism to act as a signal of individual quality or identity. [source] Ultraviolet-blue reflectance of some nestling plumage patches mediates parental favouritism in great tits Parus majorJOURNAL OF AVIAN BIOLOGY, Issue 3 2008Ismael Galván The colouration exhibited by nestling birds is generally cryptic, but in some species it has a conspicuous appearance. The adaptive function of these nestling displays is poorly known, especially in altricial species. We performed an experimental study in which the ultraviolet-blue reflectance of the carotenoid-based plumage of great tit Parus major nestlings was reduced in order to find possible evidence of parental favouritism. Tarsus length increment in a three-day period was significantly lower in manipulated nestlings than in their control siblings. As tarsus length may be a good predictor of survival, the parents may increase their fitness return by investing more in those nestlings reflecting more in the UV-blue spectral region. Interestingly, this effect was only found in a yellow patch located at the nape of nestlings that has been previously overlooked, as all the studies on plumage colouration in this species have focused on the breast plumage. Some quality indicators are proposed for the colour of nestling plumage, though the possibility exists that selection may operate through aspects of signal efficacy instead of aspects of signal content. [source] Co-evolution of plumage characteristics and winter sociality in New and Old World sparrowsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 12 2009E. A. TIBBETTS Abstract Understanding the evolution of phenotypic diversity, including the stunning array of avian plumage characters, is a central goal of evolutionary biology. Here, we applied a comparative analysis to test factors associated with the origin and maintenance of black chest and throat patches, which in some taxa are referred to as ,badges-of-status'. Specifically, we tested whether the evolution of black colour patches in Old and New World sparrows is consistent with a signalling function during the nonbreeding season or breeding season. We found no positive associations between patch evolution and polygyny or summer sociality. Instead, patch evolution is significantly associated with sociality during the nonbreeding season. Additionally, unlike typical plumage characteristics under sexual selection, these patches are visible throughout the nonbreeding season. Further, the pattern of patch dimorphism uncovered in this study does not match expectations for a trait that evolved in a reproductive context. In particular, patch dimorphism is not associated with polygyny or the presence of extra-pair mating although other types of plumage dimorphism are strongly associated with nonmonogamous mating systems. Overall, patterns of patch evolution suggest that they are more strongly associated with social competition during the nonbreeding season than sexual competition during the breeding season. These results clarify why some previous work has uncovered puzzling relationships between black plumage patches and reproductive behaviour. We discuss these findings in the context of signal theory and previous work on badges-of-status. [source] An update on the honesty of melanin-based color signals in birdsPIGMENT CELL & MELANOMA RESEARCH, Issue 2 2008Kevin J. McGraw Summary The control mechanisms and information content of melanin-based color signals in birds have generated much recent interest and controversy among evolutionary biologists. Initial experimental studies on this topic manipulated coarse metrics of an individual's condition (i.e. food intake, disease state) and failed to detect significant condition-dependence of melanin ornament expression. However, three new lines of research appear profitable and target specific factors associated with the production of melanin pigments. These include the role of (i) metals, (ii) amino acids, and (iii) testosterone and social interactions in shaping the extent and intensity of melanin-colored plumage patches. Here, I review recent studies of and evidence for these honesty-reinforcing mechanisms. [source] | ||||||||||