![\"\"](\"http:\/\/commons.wikimedia.org\/wiki\/File:Neochmia_temporalis_Cleland_2009_-_1.jpg\")
<\/a>“Red-browed Finch (Neochmia temporalis), Cleland Wildlife Park, near Mount Lofty, Adelaide, South Australia.” \u00a0Author: Peripitus<\/a><\/p><\/div>\n The researchers were most interested in carotenoid pigments, which are those that produce red, orange, and yellow coloration. This pigment was chosen not only because it is the most common one in bird bare parts, but\u00a0because animals do not produce it naturally. They instead\u00a0obtain it from their environment by eating\u00a0plants that contain the pigments (fun fact: koi fish are given carotenoid supplements to achieve their bright coloration!). Since the pigments have to be obtained from the environment, the coloration of the bill reflects what the bird has eaten, which is also tied to reproductive status and overall health. Dey et al. (2015) wanted to test the idea that carotenoid bill coloration has evolved as a social signal for things such as rank and competition for resources. \u00a0If the researchers’ hypothesis is correct, they would see a positive relationship between carotenoid bill coloration and birds that live in flocks during the non-breeding season or birds that nest in a colony.<\/p>\n Fig. 1 “Red\u2013green chromaticity colour space of passerine birds. For\u00a0each species, one point is plotted for each of the upper and lower\u00a0mandible of the male and female (i.e. four points per species).\u00a0Point colour is determined from tri-stimulus values measured from\u00a0colour plates in handbooks (see text). In the main analysis, species\u00a0were classified as having a carotenoid-based bill if their rchromaticity\u00a0score was above 0.44 (vertical line).” Dey et al. (2015)<\/p><\/div>\n To test their hypothesis, Dey et al.(2015) collected bill color data from images in the Handbook of the Birds of the World<\/em>. This allowed them to get samples fairly easily and consistently, allowing for a larger sample size. They looked at 1605 passerine species found in Africa, Australia, and New Zealand because they live in diverse areas and are fairly representative of the order. Songbirds overall are extremely diverse and widespread, and make for good subjects for study. Images were scanned, and a computer program was used to analyze the color of the birds\u2019 bills. Researchers\u00a0then paired this information with the life history traits of the birds, focusing on sociality during the non-breeding season and whether or not they are colonial, rather than dispersed, breeders. They also examined traits that were related to sexual selection such, as size and color difference between males and females (sexual dimorphism or sexual chromatism), for comaprison.<\/p>\n Fig. 3 “Percentage of species with carotenoid bill coloration as a function of (a) sociality in the nonbreeding season and (b) breeding dispersion (c) sexual size dimorphism and (d) plumage dichromatism. Numbers above each bar indicate number of species in each category. For graphical purposes only, sexual size dimorphism was considered to be present if there was at least a 4% difference in wing length between males and females. Similarly, sexual dichromatism was scored as present if there was at least a slight difference in coloration between males and females (i.e. a nonzero score for sexual dichromatism).” Dey et al. (2015)<\/p><\/div>\n The researchers did get results that aligned with their hypothesis: carotenoid bill coloration is more common in species that live in groups during the non-breeding season and in those that are colonial breeders. They also found that the coloration was not related to the traits associated with\u00a0sexual selection. These results have huge implications for the evolution of color in birds! The research suggests that carotenoid bill coloration has evolved mainly as a signal during competitive interactions rather than for sexual communication. The color of the beak can reflect the bird\u2019s overall quality as well as its dominance rank and ability to fight. While beak coloration can still be a signal used in mate selection, Dey et al.\u2019s study (2015) shows that it is more strongly associated with social grouping behaviors. Having carotenoid coloration is not as costly and inefficient as scientists once thought, and instead means\u00a0that the bird is\u00a0a fit competitor in the group.<\/p>\n For more information about the topic you can read the full article: The saying, \u201cBirds of a feather flock together\u201d is a testament to the incredibly important role bird feathers have in signaling between individuals. Birds can be found in a wide range of colors, and the\u00a0function of plumage coloration for both … Continue reading <\/a><\/a>
\nDey, C. J., Valcu, M., Kempenaers, B., & Dale, J. (2015). Carotenoid\u2010based bill coloration functions as a social, not sexual, signal in songbirds (Aves: Passeriformes). Journal of evolutionary biology<\/i>.<\/p>\n","protected":false},"excerpt":{"rendered":"