Coloration In Birds Research Articles

Cannibal

they were all born after 1975, not before. I also missed the absence of information regarding the publication of the poems: what book they belong to and whether they are unpublished. Regardless, Kercheval has drawn a sound bridge for poetry to travel from south to north. Luis Bravo University of Notre Dame Safiya Sinclair. Cannibal. Lincoln. University of Nebraska Press. 2016. 111 pages. From shards of a “hand-me-down life,” “sufficiently tragic,” Safiya Sinclair conjures poetic magic, casting a spell whereby “cannibal masters the colonial / curse.” Weaponizing Columbus’s “canibal,” misconstrued sign for the savage indigene, immortalized in Shakespeare’s anagrammatic Caliban, Sinclair wields the Monstrous (imaged on the book cover) to bare the pride, hypocrisy, and fear that underlie colonial systems of control, especially racism and patriarchy, Prospero their icon. Awarded the Whiting and Prairie Schooner prizes, Sinclair’s debut collection, “carved in our own language of the macabre,” burns with pain and fury. Merging rage and rigor, the fierce voices of her black female personae embody emancipation and revenge. African-rooted, Rasta-raised, a black island girl among white Americans, Sinclair foregrounds exile within her first four sections: at home; in America; in body; and in language. Most crucially, her personae share exile from “the lost chaos of history,” its “ghost arm” still “throttling” them. Their poems seek to claim a voice and a place in the human record. Through epigraph, allusion, and quotation , Sinclair critiques colonialism and its texts—e.g., The Tempest, Jefferson’s “Notes on the State of Virginia,” Samuel George Morton’s pseudoscientific treatise on the relative intelligence of the races—and links herself to liberationist writers, including Rimbaud, Ginsberg, O’Hara, Du Bois, Baldwin , Lorde, Brathwaite, and Césaire. Thus, for example, an epigraph from Ginsberg— “America is this correct?”—underscores the irony of “America the Beautiful,” where “every night . . . my brother is a criminal.” Cannibal pulsates with the lushness of Jamaica, its flora, fauna, rhythms, sea. “Red” weaves through it, sign of rage and menstrual blood, color of birds, hibiscus, and sargassum. The prefix “un,” meanwhile , pervades the text, modifying verbs and gerunds to describe either colonial suffering or the radical destruction of the processes producing it. Wielding Plath as a powerful influence , Sinclair censures male control. The “unbending” father in “Pocomania,” his daughter “forged in the fire of your self,” bellows “the name of his God,” the patriarchal Jah. Fragments from Caliban’s subjugated speech evoke colonialism. A white male choir intones the “unquestioning” givens of a world maintained by white supremacy, “lacquered and calm.” The god who rules woman “aches to stick an ache in my unmentionables.” Lovers seek possession , like Jefferson learning “how to belittle a thing.” One “ached to be inside, / thought he deserved to claim it.” Men are reptiles, predators: “the spotted lizard waits on my meagre life.” In this patriarchal postcolonial world, black female becomes object, “helpless in the chicken wire of my soul,” the body “an open wound,” danger and goal. Menstrual blood brings self-exile, “whole selves flushed away.” “One girl” is “branded woman overnight.” An “I” knew “what it was to be nothing / Bore the shamed blood letter of my sex / like a banishment.” Another asks, “How does it feel to be a problem? The mute centuries shatter in my ear. / The aimed black spear. This body, a crisis.” In Jamaica and America, anatomy is destiny: “Woman, wound.” Nota Bene WORLDLIT.ORG 85 Anka Muhlstein The Pen and the Brush Trans. Adriana Hunter Other Press While painting and writing are very different media, they were very influential on each other during the late nineteenth and early twentieth centuries, as French author Anka Muhlstein shows in her lively and informative biographies of Balzac, Zola, Proust, Huysmans, and Maupassant. Andrew Miller The Crossing Europa Editions Widely hailed as one of Britain’s finest writers, Andrew Miller returns with The Crossing, the story of one woman’s struggle to maintain her identity against the backdrop of expectations surrounding marriage and motherhood. Miller creates an unforgettable heroine in Maud, meticulously detailing her courage and quest for selfdetermination with his carefully crafted prose and taut plotting. But these personae flout their limits, fusing body and language to...

Evolution of iris colour in relation to cavity nesting and parental care in passerine birds

Strong selection pressures are known to act on animal coloration. Although many animals vary in eye colour, virtually no research has investigated the functional significance of these colour traits. Passeriformes have a range of iris colours, making them an ideal system to investigate how and why iris colour has evolved. Using phylogenetic comparative methods, we tested the hypothesis that conspicuous iris colour in passerine birds evolved in response to (a) coordination of offspring care and (b) cavity nesting, two traits thought to be involved in intra-specific gaze sensitivity. We found that iris colour and cooperative offspring care by two or more individuals evolved independently, suggesting that bright eyes are not important for coordinating parental care through eye gaze. Furthermore, we found that evolution between iris colour and nesting behaviour did occur in a dependent manner, but contrary to predictions, transitions to coloured eyes were not more frequent in cavity nesters than non-cavity nesters. Instead, our results indicate that selection away from having bright eyes was much stronger in non-cavity nesters than cavity nesters, perhaps because conspicuous eye coloration in species not concealed within a cavity would be more visible to predators.

Spatial summation improves bird color vision in low light intensities

Color guides many important behaviors in birds. Previously we have shown that the intensity threshold for color discrimination in the chicken depends on the color contrast between stimuli and their brightness. The birds could discriminate larger color contrasts and brighter colors in lower light intensities. We suggested that chickens use spatial summation of cone signals to maintain color vision in low light levels. Here we tested this hypothesis by determining the intensity thresholds of color discrimination using similar stimuli, patterns of grey tiles of varying intensity interspersed with color tiles, adjusted for this specific aim. Chickens could discriminate stimuli with a larger single color tile, or with a larger proportion of small color tiles, in lower light intensities. This is in agreement with the hypothesis that spatial summation improves color discrimination in low light levels. There was no difference in the intensity threshold for discrimination of stimuli with a single 6×6mm color tile, stimuli with 30% colored tiles and stimuli in which color filled the whole pattern. This gives a first indication to the degree of spatial summation that can be performed. We compare this level of spatial summation to predictions from mathematical model calculations.

The importance of cross-validation, accuracy, and precision for measuring plumage color: A comment on Vaquero-Alba et al. (2016)

ABSTRACT Vaquero-Alba and colleagues published a study in The Auk: Ornithological Advances comparing objective color measurements of plumage taken in the field directly on a bird's body to those taken in the lab on collected feathers arranged to emulate the appearance of a bird's natural plumage. Although the field measures of plumage color were less repeatable than lab measures, the authors concluded that measurements taken in the field were more representative of a bird's “true color.” Accordingly, they recommend that researchers should bring spectrophotometers into the field to measure color on live birds. We question the assumption that their field measurements represent true color and highlight concerns regarding their experimental design and methodology. Because they did not measure color of live birds in the lab or the color of plucked feathers in the field, they cannot directly test whether the assessment of color in the field on a live bird is superior. Also, rather than assume field measures are...

Iris Pattern Recognition of the Kingfisher Bird using Discrete Wavelet Transform and Feature Extraction from Histogram Orientation Gradient

Objectives: The present study has dealt with a new idea for recognizing the Iris pattern and their matching of the Kingfisher, a colorful bird. Methods/Statistical Analysis: The investigation has been made to detect, recognize and match the irises through a series of process. The work is centered about the improvement of the matrices concerned; rather than reducing the execution time of the program. For the present paper, MATLAB R2016a is used as the development tool. Findings: The proposed work is expected to give a recognition rate of 93% with a false rejected rate of 1.0. Application/Improvement: The results may be used for the census of Kingfisher birds and also towards wildlife preservation.

Colour vision and background adaptation in a passerine bird, the zebra finch (Taeniopygia guttata).

Today, there is good knowledge of the physiological basis of bird colour vision and how mathematical models can be used to predict visual thresholds. However, we still know only little about how colour vision changes between different viewing conditions. This limits the understanding of how colour signalling is configured in habitats where the light of the illumination and the background may shift dramatically. I examined how colour discrimination in zebra finch (Taeniopygia guttata) is affected by adaptation to different backgrounds. I trained finches in a two-alternative choice task, to choose between red discs displayed on backgrounds with different colours. I found that discrimination thresholds correlate with stimulus contrast to the background. Thresholds are low, and in agreement with model predictions, for a background with a red colour similar to the discs. For the most contrasting green background, thresholds are about five times higher than this. Subsequently, I trained the finches for the detection of single discs on a grey background. Detection thresholds are about 2.5 to 3 times higher than discrimination thresholds. This study demonstrates close similarities in human and bird colour vision, and the quantitative data offer a new possibility to account for shifting viewing conditions in colour vision models.

Seeing red to being red: conserved genetic mechanism for red cone oil droplets and co-option for red coloration in birds and turtles.

Avian ketocarotenoid pigments occur in both the red retinal oil droplets that contribute to colour vision and bright red coloration used in signalling. Turtles are the only other tetrapods with red retinal oil droplets, and some also display red carotenoid-based coloration. Recently, the CYP2J19 gene was strongly implicated in ketocarotenoid synthesis in birds. Here, we investigate CYP2J19 evolution in relation to colour vision and red coloration in reptiles using genomic and expression data. We show that turtles, but not crocodiles or lepidosaurs, possess a CYP2J19 orthologue, which arose via gene duplication before turtles and archosaurs split, and which is strongly and specifically expressed in the ketocarotenoid-containing retina and red integument. We infer that CYP2J19 initially functioned in colour vision in archelosaurs and conclude that red ketocarotenoid-based coloration evolved independently in birds and turtles via gene regulatory changes of CYP2J19 Our results suggest that red oil droplets contributed to colour vision in dinosaurs and pterosaurs.

Patterns of species composition of beach seine fisheries off North-Western coast of Sri Lanka, fishers’ perceptions and implications for co-management

As in many developing countries, small-scale fisheries including beach seining contribute significantly livelihoods and food security of coastal communities. Beach seining in Sri Lanka is seasonal mainly during calm season deprived of strong monsoonal winds, and essentially a multi-species fishery. Knowledge about the seasonal occurrence of pelagic species is important to be known for proper planning of the fishing activity, especially due to the reason that beach seine fishers in many parts of Sri Lanka make decisions to attach the cod-end of correct type depending on the target species. The possibility of identifying pattern of seasonal occurrence of target fish species in beach seine fishing sites off the southern region of north-western coast of Sri Lanka was therefore investigated using Self Organizing Maps (SOM). The analysis indicated that beach seine fishers’ local knowledge to predict the occurrence of certain species in the fishing sites to adjust their fishing strategies to target desirable species was consistent with the findings of SOM approach. Consequently, it was concluded that as beach seine fishers use indirect indicators such as colour of sea water and behaviour sea birds predict the species occurrence fairly accurately, their local knowledge can be incorporated in the management planning of beach seine fisheries in the North Western coastal area of Sri Lanka.

Manakins can produce iridescent and bright feather colours without melanosomes.

Males of many species often use colourful and conspicuous ornaments to attract females. Among these, male manakins (family: Pipridae) provide classic examples of sexual selection favouring the evolution of bright and colourful plumage coloration. The highly iridescent feather colours of birds are most commonly produced by the periodic arrangement of melanin-containing organelles (melanosomes) within barbules. Melanin increases the saturation of iridescent colours seen from optimal viewing angles by absorbing back-scattered light; however, this may reduce the wide-angle brightness of these signals, contributing to a dark background appearance. We examined the nanostructure of four manakin species (Lepidothrix isidorei, L. iris, L. nattereri and L. coeruleocapilla) to identify how they produce their bright plumage colours. Feather barbs of all four species were characterized by dense and fibrous internal spongy matrices that likely increase scattering of light within the barb. The iridescent, yet pale or whitish colours of L. iris and L. nattereri feathers were produced not by periodically arranged melanosomes within barbules, but by periodic matrices of air and β-keratin within barbs. Lepidothrix iris crown feathers were able to produce a dazzling display of colours with small shifts in viewing geometry, likely because of a periodic nanostructure, a flattened barb morphology and disorder at a microstructural level. We hypothesize that iridescent plumage ornaments of male L. iris and L. nattereri are under selection to increase brightness or luminance across wide viewing angles, which may potentially increase their detectability by females during dynamic and fast-paced courtship displays in dim light environments.

Multitrait aposematic signal in Batesian mimicry

Batesian mimics can parasitize Müllerian mimicry rings mimicking the warning color signal. The evolutionary success of Batesian mimics can increase adding complexity to the signal by behavioral and locomotor mimicry. We investigated three fundamental morphological and locomotor traits in a Neotropical mimicry ring based on Ithomiini butterflies and parasitized by Polythoridae damselflies: wing color, wing shape, and flight style. The study species have wings with a subapical white patch, considered the aposematic signal, and a more apical black patch. The main predators are VS-birds, visually more sensitive to violet than to ultraviolet wavelengths (UVS-birds). The white patches, compared to the black patches, were closer in the bird color space, with higher overlap for VS-birds than for UVS-birds. Using a discriminability index for bird vision, the white patches were more similar between the mimics and the model than the black patches. The wing shape of the mimics was closer to the model in the morphospace, compared to other outgroup damselflies. The wing-beat frequency was similar among mimics and the model, and different from another outgroup damselfly. Multitrait aposematic signals involving morphology and locomotion may favor the evolution of mimicry rings and the success of Batesian mimics by improving signal effectiveness toward predators.

Genetic Basis for Red Coloration in Birds

The yellow and red feather pigmentation of many bird species [1] plays pivotal roles in social signaling and mate choice [2, 3]. To produce red pigments, birds ingest yellow carotenoids and endogenously convert them into red ketocarotenoids via an oxidation reaction catalyzed by a previously unknown ketolase [4-6]. We investigated the genetic basis for red coloration in birds using whole-genome sequencing of red siskins (Spinus cucullata), common canaries (Serinus canaria), and "red factor" canaries, which are the hybrid product of crossing red siskins with common canaries [7]. We identified two genomic regions introgressed from red siskins into red factor canaries that are required for red coloration. One of these regions contains a gene encoding a cytochrome P450 enzyme, CYP2J19. Transcriptome analysis demonstrates that CYP2J19 is significantly upregulated in the skin and liver of red factor canaries, strongly implicating CYP2J19 as the ketolase that mediates red coloration in birds. Interestingly, a second introgressed region required for red feathers resides within the epidermal differentiation complex, a cluster of genes involved in development of the integument. Lastly, we present evidence that CYP2J19 is involved in ketocarotenoid formation in the retina. The discovery of the carotenoid ketolase has important implications for understanding sensory function and signaling mediated by carotenoid pigmentation.

Fruit color preference by birds and applications to ecological restoration.

Ecological restoration aims to retrieve not only the structure but also the functionality of ecosystems. Frugivorous birds may play an important role in this process due to their efficiency in seed dispersal. Color perception in these animals is highly developed, and then the colors of fleshy fruits may provide important clues for choosing plant species for restoration plans. This study aims to integrate bird color preferences and restoration of degraded areas, with an objective to evaluate the potential attractiveness to birds by colored fruits. We carried out an experiment with 384 artificial fruits made of edible modeling clay with the following colors: black, blue, green and red, with 96 fruits of each color in six sites, including four restored areas and two second-growth forest fragments. We also tested the possible effect of light intensity on fruit consumption by color. A total of 120 (38.6%) were assumed to be consumed by birds, and the fruit consumption varied in response to the location and light incidence. Consumption of black and blue fruits was not related to site by chance. Notwithstanding, red and black fruits were consumed significantly more than any other colors, emphasizing bird preference to these colors, regardless of location. Enrichment with shade tolerant shrubs or forest species with black or red fruits may be an alternative way to manage established restorations. In recently established or new restorations, one may introduce pioneer shrubs or short-lived forest species which have blue fruits, but also those having black or red ones.

Bird Integumentary Melanins: Biosynthesis, Forms, Function and Evolution.

Melanins are the ubiquitous pigments distributed in nature. They are one of the main pigments responsible for colors in living cells. Birds are among the most diverse animals regarding melanin-based coloration, especially in the plumage, although they also pigment bare parts of the integument. This review is devoted to the main characteristics of bird melanins, including updated views of the formation and nature of melanin granules, whose interest has been raised in the last years for inferring the color of extinct birds and non-avian theropod dinosaurs using resistant fossil feathers. The molecular structure of the two main types of melanin, eumelanin and pheomelanin, and the environmental and genetic factors that regulate avian melanogenesis are also presented, establishing the main relationship between them. Finally, the special functions of melanin in bird feathers are also discussed, emphasizing the aspects more closely related to these animals, such as honest signaling, and the factors that may drive the evolution of pheomelanin and pheomelanin-based color traits, an issue for which birds have been pioneer study models.

Aberrant Colouration in the Atlantic Puffin (<i>Fratercula arctica</i>), the Common Murre (<i>Uria aalge</i>), and the Thick-billed Murre (<i>U. lomvia</i>) from Atlantic Canada

The colour of birds’ plumage and bare parts is an important feature in choice of mate, camouflage, thermoregulation, species recognition, and flight mechanics. Abnormalities in colouration occur in a variety of species and can have important consequences for an individual’s survival and fitness. We present 7 new cases of colouration abnormalities in 3 species of auk (Alcidae) and review previous reports to correctly assign the proper form of abnormality to specimens in museums or photographs. Of the 53 reported colouration abnormalities, we reclassified 42, progressive greying being the most common (18 or 19 cases out of 42, 43–45%), followed by brown (10/42 cases, 24%), in addition to 6 cases of melanism, 4 of dilution, 2 of partial leucism, and 1 likely somatic mutation. Properly describing the form of colour abnormality improves our understanding of the frequency, causes, and consequences of aberrant colouration.

Shedding Light on Bird Egg Color: Pigment as Parasol and the Dark Car Effect.

The vibrant colors of many birds' eggs, particularly those that are blue to blue-green, are extraordinary in that they are striking traits present in hundreds of species that have nevertheless eluded evolutionary functional explanation. We propose that egg pigmentation mediates a trade-off between two routes by which solar radiation can harm bird embryos: transmittance through the eggshell and overheating through absorbance. We quantitatively test four components of this hypothesis on variably colored eggs of the village weaverbird (Ploceus cucullatus) in a controlled light environment: (1) damaging ultraviolet radiation can transmit through bird eggshells, (2) infrared radiation at natural intensities can heat the interior of eggs, (3) more intense egg coloration decreases light transmittance ("pigment as parasol"), and (4) more intense egg coloration increases absorbance of light by the eggshell and heats the egg interior ("dark car effect"). Results support all of these predictions. Thus, in sunlit nesting environments, less pigmentation will increase the detrimental effect of transmittance, but more pigmentation will increase the detrimental effect of absorbance. The optimal pigmentation level for a bird egg in a given light environment, all other things being equal, will depend on the balance between light transmittance and absorbance in relation to embryo fitness.

Safety and efficacy of copper complexes of chlorophylls for ornamental fish, grain‐eating ornamental birds and small rodents and of copper complexes of chlorophyllins for all animal species

Copper complexes of chlorophylls are applied as colourants used for ornamental fish, grain-eating ornamental birds and small rodents (subgroup: substances which favourably affect the colour of ornamental fish or birds). Copper complexes of chlorophyllins are applied as a colourant to add colour to feedingstuffs of cats and dogs and all animal species and for all animal species for use in certain groups of feed materials. In the absence of adequate data on absorption, distribution, metabolism and excretion, genotoxicity, subchronic and chronic toxicity, carcinogenicity, and reproductive and developmental toxicity of copper complexes of chlorophyllins, the Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) could not conclude on the safety of this additive for the consumer. No data on the tolerance of target animals were provided. In the absence of adequate toxicological data that would allow deriving a no observed adverse effect level (NOAEL) and to exclude the genotoxic potential, the FEEDAP Panel could not conclude on the safety of copper complex of chlorophylls and copper complex of chlorophyllins for the target animals. In the absence of data the FEEDAP Panel cannot conclude on the safety for the user of the additives. No risks to the environment are expected from the use of copper complexes of chlorophylls or copper complexes of chlorophyllins in animal nutrition. The FEEDAP Panel is not in the position to conclude (i) on the efficacy of copper complexes of chlorophylls to colour ornamental fish, grain-eating ornamental birds and small rodents, and (ii) on the concentrations of copper complexes of chlorophylls and of chlorophyllins necessary to visibly colour feed of cats and dogs, ornamental birds, small rodents and certain feed materials for all animal species.

Confined disordered strictly jammed binary sphere packings.

Disordered jammed packings under confinement have received considerably less attention than their bulk counterparts and yet arise in a variety of practical situations. In this work, we study binary sphere packings that are confined between two parallel hard planes and generalize the Torquato-Jiao (TJ) sequential linear programming algorithm [Phys. Rev. E 82, 061302 (2010)] to obtain putative maximally random jammed (MRJ) packings that are exactly isostatic with high fidelity over a large range of plane separation distances H, small to large sphere radius ratio α, and small sphere relative concentration x. We find that packing characteristics can be substantially different from their bulk analogs, which is due to what we term "confinement frustration." Rattlers in confined packings are generally more prevalent than those in their bulk counterparts. We observe that packing fraction, rattler fraction, and degree of disorder of MRJ packings generally increase with H, though exceptions exist. Discontinuities in the packing characteristics as H varies in the vicinity of certain values of H are due to associated discontinuous transitions between different jammed states. When the plane separation distance is on the order of two large-sphere diameters or less, the packings exhibit salient two-dimensional features; when the plane separation distance exceeds about 30 large-sphere diameters, the packings approach three-dimensional bulk packings. As the size contrast increases (as α decreases), the rattler fraction dramatically increases due to what we call "size-disparity" frustration. We find that at intermediate α and when x is about 0.5 (50-50 mixture), the disorder of packings is maximized, as measured by an order metric ψ that is based on the number density fluctuations in the direction perpendicular to the hard walls. We also apply the local volume-fraction variance σ(τ)(2)(R) to characterize confined packings and find that these packings possess essentially the same level of hyperuniformity as their bulk counterparts. Our findings are generally relevant to confined packings that arise in biology (e.g., structural color in birds and insects) and may have implications for the creation of high-density powders and improved battery designs.

The colour of an avifauna: A quantitative analysis of the colour of Australian birds.

Animal coloration is a poorly-understood aspect of phenotypic variability. Here I expand initial studies of the colour gamut of birds by providing the first quantitative description of the colour variation of an entire avifauna: Australian landbirds (555 species). The colour of Australian birds occupies a small fraction (19%) of the entire possible colour space and colour variation is extremely uneven. Most colours are unsaturated, concentrated in the centre of colour space and based on the deposition of melanins. Other mechanisms of colour production are less common but account for larger portions of colour space and for most saturated colours. Male colours occupy 45–25% more colour space than female colours, indicating that sexual dichromatism translates into a broader range of male colours. Male-exclusive colours are often saturated, at the edge of chromatic space, and have most likely evolved for signalling. While most clades of birds occupy expected or lower-than-expected colour volumes, parrots and cockatoos (Order Psittaciformes) occupy a much larger volume than expected. This uneven distribution of colour variation across mechanisms of colour production, sexes and clades is probably shared by avifaunas in other parts of the world, but this remains to be tested with comparable data.

A ORIGEM DA NOITE E POR QUE O SOL É CHAMADO DE "FOLHA DE CARANÁ"

Resumo A partir da análise de um amplo conjunto de narrativas sobre a origem da noite, obtidas junto aos povos indígenas da bacia do Alto Rio Negro no noroeste amazônico, este artigo explora o modo como esses povos representam a alternância entre o dia e a noite em diferentes planos de significantes - nos sons e cores dos insetos, pássaros e animais da floresta; nos materiais, texturas e cores de suas casas e objetos; no corpo humano; e na música e na dança rituais. Este último plano nos permitirá compreender o ritual como um mecanismo de controle do tempo. Além disso, espero lançar luz sobre as razões pelas quais, em muitas línguas da família Tukano Oriental, os termos para "sol" e para "lua" significam também, respectivamente, "colmo" e "folha".

A reliable technique to quantify the individual variability of iridescent coloration in birds

The study of iridescent coloration in birds emerged only recently, mainly due to the difficulty inherent in quantifying its directionality. Directionality restrains color perception to a limited angle and thereby causes drastic changes in brightness when an animal is in motion. Although a versatile goniometer for quantifying iridescent coloration has been developed recently, so far, it has only been applied to measuring the highly directional iridescent coloration in a hummingbird species. Thus, the reliability of the goniometer for species displaying more common and less directional iridescent coloration has yet to be evaluated. Additionally, two important methodological aspects remain to be assessed before this apparatus can be used confidently: 1) whether directionality, which could be subject to sexual selection, can be quantified in a repeatable way; and 2) whether the apparatus gives more precise and accurate measurements than a less complex traditional method. Using feathers collected from 271 male tree swallows Tachycineta bicolor over two years, we found that the goniometer provided repeatable measurements of directionality across individuals and across three body regions, namely the crown, mantle and rump. The apparatus was also more repeatable than a traditional method involving a bifurcated probe and reduced a brightness bias associated with individual differences in barbule tilt. We strongly encourage researchers to invest in this methodological change considering the multiple advantages demonstrated and to quantify the directionality of iridescent coloration as to unveil its role in signaling and sexual selection.