Feather Barbs Research Articles

A Surface‐based Appearance Model for Pennaceous Feathers

AbstractThe appearance of a real‐world feather results from the complex interaction of light with its multi‐scale biological structure, including the central shaft, branching barbs, and interlocking barbules on those barbs. In this work, we propose a practical surface‐based appearance model for feathers. We represent the far‐field appearance of feathers using a BSDF that implicitly represents the light scattering from the main biological structures of a feather, such as the shaft, barb and barbules. Our model accounts for the particular characteristics of feather barbs such as the non‐cylindrical cross‐sections and the scattering media via a numerically‐based BCSDF. To model the relative visibility between barbs and barbules, we derive a masking term for the differential projected areas of the different components of the feather's microgeometry, which allows us to analytically compute the masking between barbs and barbules. As opposed to previous works, our model uses a lightweight representation of the geometry based on a 2D texture, and does not require explicitly representing the barbs as curves. We show the flexibility and potential of our appearance model approach to represent the most important visual features of several pennaceous feathers.

Occurrence of Novel and Legacy Per/Polyfluoroalkyl Substances (PFASs) in Scopoli’s Shearwater (Calonectris diomedea) Feathers

Per- and polyfluoroalkyl substances (PFASs) are contaminants of great concern due to their ubiquitous environmental occurrence in the environment and their potential adverse effects on organisms. There is currently limited information regarding the occurrence of PFASs in Scopoli’s Shearwater (Calonectris diomedea). In this study, two feather samples per bird were obtained from 26 adults on Strofades colony (Ionian Sea/Greece) during the early phase of the chick-rearing period (late July 2019). The samples consisted of barbs and barbules of the primary feathers, P1 and P10, reflecting pollution pressures at the time and the place of feather growth, i.e., at the species’ breeding and wintering grounds for P1 and P10, respectively. There were 25 PFAS detected in the feathers, with detection rates ranging from 2% (perfluorododecanoic acid—PFDoDA; perfluorohexane sulfonate—PFHxS; 9-chlorohexadecafluoro-3-oxanonane-1-sulfonate—9Cl-PF3ONS; 2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)propanoate—Gen-X) to 98% (sodium 1H,1H,2H,2H-perfluorooctane sulfonate; 6:2 FTSA). ∑PFAS ranged from 25.93 ng/g to 426.86 ng/g of feather sample. The highest mean concentration (109.10 ng/g feather) was reported for perfluorononanoic acid (PFNA). No significant differences in PFAS concentrations with high detection rate (>20%) were found according to the sex of the birds. PFAS concentrations with a detection rate > 20% in the P1 vs. P10 feathers of Scopoli’s Shearwater adults were not significantly different, reflecting the fact that breeding grounds in the Mediterranean and wintering grounds in the Atlantic seem to be contaminated with similar PFASs levels, even though some compounds showed regional trends.

Development and Characterization of Hybrid Particulate-fiber Reinforced Epoxy Composites

Although considered wastes, animal fibers and gastropod shell particles are biodegradable, have low density, high stiffness, considerably high impact absorption capacity and relatively low cost. Therefore, they are finding increasing use as reinforcement materials in polymer composites. This research work studied the tensile, hardness, and wear resistance properties of hybrid snail shell (SSP) and chicken feather barb fibers (CFB) reinforced epoxy composites. The stir cast molding technique was utilized to synthesize the composite samples with 3, 6, 9, 12, 15, and 18 wt.% of the hybrid SSPs/CFB. Compared with the control samples, SSP/CFB hybrid reinforcements enhanced the mechanical properties of the composites. Composites with intermediate weight fraction of 9 wt.% SSP/CFB exhibited overall optimum properties when benchmarked against the control sample with approximately 37, 37, 133, 19, and 59% improvement in wear, hardness, impact, and ultimate tensile strength properties respectively. These enhancements suggested a synergistic effect of the two reinforcement phases. The results presented in this study demonstrated the potential of utilizing bio-derived waste materials for synthesizing eco-friendly composites.

Prediction of individual differences in non-iridescent structural plumage colour from nanostructural periodicity and regularity.

Non-iridescent structural plumage reflectance is a sexually selected indicator of individual quality in several bird species. However, the structural basis of individual differences remains unclear. In particular, the dominant periodicity of the quasi-ordered feather barb nanostructure is of key importance in colour generation, but no study has successfully traced back reflectance parameters, and particularly hue, to nanostructural periodicity, although this would be key to deciphering the information content of individual variation. We used matrix small-angle X-ray scattering measurements of intact, stacked feather samples from the blue tit crown to estimate the sex-dependence and individual variation of nanostructure and its effects on light reflectance. Measures of nanostructural periodicity successfully predicted brightness, ultraviolet chroma and also hue, with statistically similar effects in the two sexes. However, we also observed a lack of overall effect of the nanostructural inhomogeneity estimate on reflectance chromaticity, sex-dependent accuracy in hue prediction and strong sex-dependence in position estimation error. We suggest that reflectance attributes are modified by other feather structures in a sex-specific manner, and that within-individual variation in nanostructural parameters exists within or among feathers and this confounds the interpretation of structure-reflectance relationships at the plumage area level.

Empirically tuned theory reveals why symbiont abundance 'mite' vary across hosts.

Research Highlight: del Mar Labrador, M., Serrano, D., Doña, J., Aguilera, E., Arroyo, J. L., Atiénzar, F., Barba, E., Bermejo, A., Blanco, G., Borràs, A., Calleja, J. A., Cantó, J. L., Cortés, V., de la Puente, J., de Palacio, D., Fernández-González, S., Figuerola, J., Frías, Ó., Fuertes-Marcos, B. Garamszegi, L. Z., Gordo, Ó., Gurpegui, M., Kovács, I., Martínez, J. L., Meléndez, L., Mestre, A., Møller, A. P., Monrós, J. S., Moreno-Opo, R., Navarro, C., Pap, P. L., Pérez-Tris, J., Piculo, R., Ponce, C., Proctor, H., Rodríguez, R., Sallent, Á., Senar, J., Tella, J. L., Vágási, C. I., Vögeli, M., & Jovani, R. (2023). Host space, not energy or symbiont size, constrains feather mite abundance across passerine bird species. Journal of Animal Ecology, https://doi.org/10.1111/1365-2656.14032. Symbionts represent crucial links between species in ecosystems. Consequently, understanding their patterns of abundance is a major goal in the study of symbioses. However, multiple biotic and abiotic factors may regulate symbionts, and disentangling the mechanisms that drive variation in their abundance across host species is challenging. One promising strategy to approach this challenge is to incorporate biologically relevant data into theoretical models. In a recent study, Labrador etal. (2023) used this strategy to investigate the poorly understood symbiosis between feather mites and their avian hosts. They integrate a remarkable amount of empirical data with models based on the metabolic theory of ecology to determine what factors limit feather mite abundance across European passerines. Their quantitative analyses indicate that the number of feather barbs limits mite abundance across host species, suggesting that mite populations are spatially, but not energetically, constrained. These findings not only reveal mechanisms that may drive the variation in feather mite abundances across hosts, but also advance our understanding of the ecology of interspecific interactions more generally.

Host space, not energy or symbiont size, constrains feather mite abundance across passerine bird species.

Comprehending symbiont abundance among host species is a major ecological endeavour, and the metabolic theory of ecology has been proposed to understand what constrains symbiont populations. We parameterized metabolic theory equations to investigate how bird species' body size and the body size of their feather mites relate to mite abundance according to four potential energy (uropygial gland size) and space constraints (wing area, total length of barbs and number of feather barbs). Predictions were compared with the empirical scaling of feather mite abundance across 106 passerine bird species (26,604 individual birds sampled), using phylogenetic modelling and quantile regression. Feather mite abundance was strongly constrained by host space (number of feather barbs) but not by energy. Moreover, feather mite species' body size was unrelated to the body size of their host species. We discuss the implications of our results for our understanding of the bird-feather mite system and for symbiont abundance in general.

The fruit dispersion of Adenostemma brasilianum (Asteraceae) by birds: an experimental approach

ABSTRACT The pantropical genus Adenostemma (Asteraceae) includes mostly herbs which occur in wet forests and stream edges. They produce a large number of small fruits or cypselae, covered by glandular hairs and bearing a particular glandular pappus. These morphological characteristics of the fruits have been associated, but never tested, with dispersion by adhesion to birds’ feathers. We developed for the first time an experimental study to demonstrate the ability of the fruits of Adenostemma brasilianum (Pers.) Cass. to adhere to birds’ feathers. We performed three different experiments to test both the adherence and retention time of the fruits, with: 1) individual feathers, 2) taxidermied birds mounted in a life-like position, and 3) live captive birds. The fruits were effective in attaching to feather barbs under the three experiments and were able to remain attached for a period of time, supporting previous hypotheses that epiornithochory could be directly involved in the process of fruit dispersion. Our results are especially relevant in the understanding of biogeographic patterns in Adenostemma, given the importance of birds as fruit dispersion agents.

Mutations in SLC45A2 lead to loss of melanin in parrot feathers.

Bird plumage coloration is a complex and multifactorial process that involves both genetic and environmental factors. Diverse pigment groups contribute to plumage variation in different birds. In parrots, the predominant green color results from the combination of 2 different primary colors: yellow and blue. Psittacofulvin, a pigment uniquely found in parrots, is responsible for the yellow coloration, while blue is suggested to be the result of light scattering by feather nanostructures and melanin granules. So far, genetic control of melanin-mediated blue coloration has been elusive. In this study, we demonstrated that feather from the yellow mutant rose-ringed parakeet displays loss of melanosome granules in spongy layer of feather barb. Using whole genome sequencing, we found that mutation in SLC45A2, an important solute carrier protein in melanin synthetic pathway, is responsible for the sex-linked yellow phenotype in rose-ringed parakeet. Intriguingly, one of the mutations, P53L found in yellow Psittacula krameri is already reported as P58A/S in the human albinism database, known to be associated with human OCA4. We further showed that mutations in SLC45A2 gene affect melanin production also in other members of Psittaculidae family such as alexandrine and plum-headed parakeets. Additionally, we demonstrate that the mutations associated with the sex-linked yellow phenotype, localized within the transmembrane domains of the SLC45A2 protein, affect the protein localization pattern. This is the first evidence of plumage color variation involving SLC45A2 in parrots and confirmation of associated mutations in the transmembrane domains of the protein that affects its localization.

PHEROMONE COMMUNICATION IN FEATHER-FEEDING WING LICE (INSECTA: PHTHIRAPTERA).

Pheromone communication is central to the life history of insect parasites. Determining how pheromones affect parasite behavior can provide insights into host-parasite interactions and suggest novel avenues for parasite control. Lice infest thousands of bird and mammal species and feed on the host's feathers or blood. Despite the pervasiveness of lice in wild populations and the costs they exact on livestock and poultry industries, little is known about pheromone communication in this diverse group. Here, we test for pheromone communication in the wing lice (Columbicola columbae) of Rock Doves (Columba livia). Wing lice spend the majority of their lives on bird flight feathers where they hide from host preening by inserting their bodies between coarse feather barbs. To feed, wing lice must migrate to bird body regions where they consume the insulating barbs of contour feathers. We first show that wing lice readily form aggregations on flight feathers. Next, using a Y-tube olfactometer, we demonstrate that wing lice use pheromone communication to move toward groups of nearby conspecifics. This pheromone is likely an aggregation pheromone, as wing lice only produce the pheromone when placed on flight feathers. Finally, we found that when forced to choose between groups of male and female lice, male lice move toward male groups and females toward female groups, suggesting the use of multiple pheromones. Ongoing work aims to determine the chemical identity and function of these pheromones.

Carotenoid-dependent plumage coloration is associated with reduced male care in passerine birds

AbstractThe immense diversity of plumage coloration exhibited by birds is the result of either pigments deposited in the feathers or microstructural arrangements of feather barbules. Some of the most common pigments are carotenoids, which produce bright yellow, orange, and red colors. Carotenoids differ from other pigments since birds cannot synthesize them de novo and must obtain them from the diet. Carotenoid pigments are usually associated with signaling and sexual selection, although they also have antioxidant properties and play a role in the immune response. Here, we hypothesize that carotenoid-dependent plumage coloration functions as a signal of a male’s tendency to invest in offspring care because they play an important role in self-maintenance and may provide key information about individual quality; allowing females to obtain information about a male’s tendency to invest in offspring care. Using phylogenetic comparative analyses across 349 passerine birds, we show that species that consume carotenoid-rich foods have more carotenoid-dependent plumage coloration than species with carotenoid-poor diets. In addition, carotenoid-dependent plumage coloration is associated with decreased male investment in offspring care. Our results suggest that investment in carotenoid-dependent plumage coloration trades off against male investment in offspring care and will likely have broad implications for our understanding of the ecological contexts that facilitate various evolutionary processes, such as sexual selection and signaling associated with plumage colors.

The penguin feather as inspiration for anti-icing surfaces

Understanding how to influence ice adhesion to structures and prevent icing catastrophes is a paramount research question. Conventional industrial anti-icing methods are active, requiring an energy source. However, active strategies are energy intensive. Passive anti-icing surfaces have thus become an area of engineering interest. Such strategies, like low surface energy chemical coatings, produce highly anti-icing surfaces on a lab-scale but they have not succeeded in industrial applications. They lack efficacy over repeated icing/de-icing cycles and their materials are unsuited for harsh environments. The body feather of the sub-Antarctic Gento penguin Pygoscelis papua, which ornithologists note is perpetually free of ice despite its freezing environment, serves as a compelling source of passive anti-icing biomimetic inspiration which may overcome these aforementioned deficiencies. Through studying these feathers, it has become clear that two aspects of anti-icing (water-shedding and ice-shedding) are addressed in distinct ways by the Gentoo penguin. The water-shedding functionality of the feathers is derived from an air cushion created by the wire-like microstructure of the feather and is augmented by nano-scale grooves in the feather coated in preen oil. The preen oil is necessary to maintain water-shedding functionality, however once removed the ice-shedding functionality of the feathers is maintained. The ice-shedding functionality appears to be derived from wire-like morphology of the penguin body feather barbs and barbules which induce cracks that are easily opened at the ice-feather interface. Such a design strategy shows promise in addressing the common failings of passive systems. These anti-icing strategies were then tested on metallic biomimetic substrates. The barb structure of the penguin body feather was mimicked using ultra-fine woven stainless-steel wire cloth. Some stainless-steel wire cloths were laser machined to mimic the texturing and surface chemistry of the feathers. These cloths were indeed hydrophobic like the feathers. Both stainless-steel wire cloths had significantly reduced ice adhesion strengths compared to those of the flat monolithic stainless-steel sample. The laser-machined wire cloth had an ice adhesion strength of 63 ± 10 kPa compared to 603 ± 236 kPa for the flat sample. This both indicates that the ice-shedding capabilities of the sample are imparted by the structure and further strengthens the argument that water-shedding and ice-shedding are distinct phenomena that need to be addressed with two separate design strategies.

Transglutaminase Activity Is Conserved in Stratified Epithelia and Skin Appendages of Mammals and Birds.

The cross-linking of structural proteins is critical for establishing the mechanical stability of the epithelial compartments of the skin and skin appendages. The introduction of isopeptide bonds between glutamine and lysine residues depends on catalysis by transglutaminases and represents the main protein cross-linking mechanism besides the formation of disulfide bonds. Here, we used a fluorescent labeling protocol to localize the activity of transglutaminases on thin sections of the integument and its appendages in mammals and birds. In human tissues, transglutaminase activity was detected in the granular layer of the epidermis, suprabasal layers of the gingival epithelium, the duct of sweat glands, hair follicles and the nail matrix. In the skin appendages of chickens, transglutaminase activity was present in the claw matrix, the feather follicle sheath, the feather sheath and in differentiating keratinocytes of feather barb ridges. During chicken embryogenesis, active transglutaminase was found in the cornifying epidermis, the periderm and the subperiderm. Transglutaminase activity was also detected in the filiform papillae on the tongue of mice and in conical papillae on the tongue of chickens. In summary, our study reveals that transglutaminase activities are widely distributed in integumentary structures and suggests that transglutamination contributes to the cornification of hard skin appendages such as nails and feathers.

DIFFERENCES IN BIOACCUMULATION OF HEAVY METALS AND METALLOIDS BETWEEN BARBS AND CALAMUS OF TAIL FEATHERS OF WHITE BACKED VULTURES (GYPS AFRICANUS)

Current study was designed to validate the use of tail feathers as non-invasivebiomonitoring tool and to compare its barb and calamus parts for bioaccumulation of heavy metals viz.Cd, Cr, Pb, Cu, Hg and As in white backed vulture (Gyps africanus). A total of 8 tail feathers samplescollected from eight birds were analyzed. All the studied heavy metals except Hg and As were detectedin tail feathers of G. Africanus. We corroborated the use of tail feathers as non-invasive biomonitoringtool for all the heavy metals except Hg and As. In general, metals in feathers followed the trend asPb>Cd>Cr>Cu. Concentrations of trace metals were higher in barbs than calamus reflecting possibleexternal deposition. Comparison of heavy metals revealed non-significant (P> 0.05) differencesbetween barbs and calamus parts. We concluded that barbs of feathers are promising biomonitoringtool for metals contamination.

Microscopic fibres in soils – The accumulation of textile fibres and animal hairs at the 6th–11th-century CE Kvarnbo Hall settlement site on the Åland Islands, Finland

Microscopic animal and plant fibres detected in archaeological contexts are a valuable source of information regarding textile production, use-histories of artefacts and in studying mortuary practices. At the same time, recent research on microplastic pollution has revealed the ability of fibres to move even long distances and accumulate in various terrestrial and aquatic contexts. In this paper we discuss the accumulation of 100–1000-µm-long animal hairs, bird feather barbules and textile fibres at Kvarnbo Hall, a Nordic Late Iron Age high-status settlement site in the Åland Archipelago, Finland. The hairs and barbules detected in soil samples reveal important information on the use of furs and downy feathers at the site. However, our study reveals that the microparticles sampled in the 6th–11th-century contexts represent not only the prehistoric phase of the site but can also be ascribed to the later land-use history of the area. We also speculate that long-distance air-borne particles might be one possible contamination source of fibres.

Further Information about the Nest, Eggs and Nestlings of the Copper-Rumped Hummingbird Saucerottia tobaci from Venezuela

The Copper-rumped Hummingbird Saucerottia tobaci is a polyphyletic hummingbird with seven recognized subspecies. Nonetheless, the most information on its nesting behavior come from the island race S. t. erythronotos. This study aims to describe a nesting event of S. t. feliciae, the most widespread mainland subspecies, in order to provide detailed information on its nest structure, eggs and nestling development, as well as report information related to the nesting success (survival strategies, potential threats), based on observations carried out from August to October 2021 in northern Venezuela. Features of nest (composition, form, dimensions), eggs (appearance, dimensions, mass) and nestling development data from hatching to fledging time (body length, bill, wings, tail, and body mass) were all recorded in detail. The nest was an open saddle-type, cream in color, built of silky vegetable down, silky fibers of moth cocoon, mossy stuffs, pieces of lichen and spider’s web. Nest dimensions (mm): outer-cup depth: 40.7; inner-cup depth: 18.0; base-bed: 22.7; cup-rim thickness: 10.0–12.0; cup-rim length: 40.4; cup-rim wide: 18.4. Two oval-shaped eggs were laid inside, white in color, without spots or blots, smooth in texture, and non-glossy. Egg mass (0.6 ± 0 g; n = 2), egg length (13.95 ± 0.07 mm; n = 2), egg width (9.4 ± 0.14 mm; n = 2). Both eggs were incubated during 16 days. Nestlings were born almost completely naked, dark skin above, reddish beige below; bill yellow with the tip red and blunt; eyes closed. Nestling body mass at hatching (0.6 ± 0 g, n = 2), fledgling period (23 days). First feather barbs (day 10), eyes open (day 10), nestling totally feathered (day 16), and nestling body mass at fledging (4.7 g, n = 1). Survival strategies were nest camouflage, roof protection, female motionlessness, distraction displays and mobbing behavior. The nest was also close to a bumblebee nest and an artificial feeder. Potential threats included nest predators and heavy rains. This study introduces novel information on nesting behavior of a mainland subspecies and suggests that S. t. feliciae resembles S. t. erythronotos with slight differences in terms of nest construction, and eggs mass and length. Data on other nests, including those of other Venezuelan subspecies, are necessary to fully categorize the nesting behavior of this hummingbird in order to identify critical subspecific elements (e. g. nest materials, nestling´s food, human impact, additional nest predators and parasites) needed for its conservation in future.

Light to intermediate oil sheens increase Manx shearwater feather permeability.

Oil pollution has profound negative impacts on the marine environment, with seabirds particularly vulnerable to oiling, due to the amount of time spent on the sea surface foraging or resting. Exposure to oil can affect feather structure and influence waterproofing, buoyancy and thermoregulation. We investigated the effects of surface crude oil on the feather structure of Manx shearwaters (Puffinus puffinus), a seabird species that spends a high proportion of time on the water surface. Sampled body contour feathers were exposed to varying thicknesses of surface crude oil before assessing their resistance to water permeation, increase in mass and clumping of feather barbules. Surface oil as thin as 0.1 µm was enough to increase feather permeability, while greatest impacts on permeability were caused by exposure to dark colour surface sheens 3 µm in thickness. Increases in feather mass of up to 1000% were noted in heavy oiling scenarios due to contact with thicker oil slicks, which may significantly affect wing loading and energetic expenditure.

Beyond dirty teeth: Integrating dental calculus studies with osteoarchaeological parameters

The study of ancient human dental calculus (mineralized dental plaque, also known as tartar) is becoming increasingly important in osteoarchaeology, human palaeoecology and environmental archaeology. Microremains of different origin (e.g. starch granules, pollen, phytoliths, feather barbules) as well as biomolecules and chemical compounds retrieved from its mineral matrix may represent an important link between past humans and their physical, biological and social environment, but they are rarely fully linked to the evidence from skeletal remains. This paper critically reviews the lines of evidence retrieved from dental calculus in relation to osteoarchaeological parameters, employing macroscopic, microscopic and biomolecular approaches, assessing synergy potential and limitations. The scope of this paper is also to contribute to the building of a much needed theoretical framework in this emerging subfield.

A remarkable assemblage of ticks from mid-Cretaceous Burmese amber.

AbstractFour fossil ticks (Arachnida: Parasitiformes: Ixodida) are described from mid-Cretaceous (ca. 100 Ma) Burmese amber of Myanmar.Ixodes antiquorumsp. nov. (Ixodidae) is the first Mesozoic record ofIxodesand the oldest representative of the most species-rich extant tick genus. Its affinities appear to lie with modern Australian forms, consistent with the hypothesis that Burmese amber hosted Gondwanan faunal elements. Even more remarkable isKhimaira fossusgen. et sp. nov. which combines a body resembling that of a soft tick (Argasidae) with a basis capitulum more like that of a hard tick (Ixodidae). We refer it to Khimairidae fam. nov. as a possible transitional form between the two main families of ticks alive today. Another member of the extinct Deinocrotonidae is described asDeinocroton copiasp. nov., while the first described adult female forCornupalpatum burmanicumis associated with a dinosaur feather barb.

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Cortex Thickness Is Key for the Colors of Iridescent Starling Feather Barbules With a Single, Organized Melanosome Layer

The iridescent plumage of many birds is structurally colored due to an orderly arrangement of melanosomes in their feather barbules. Here, we investigated the blue- to purple-colored feathers of the European starling (Sturnus vulgaris) and the blue and green feathers of the Cape starling (Lamprotornis nitens). In both cases, the barbules contain essentially a single layer of melanosomes, but in S. vulgaris they are solid and rod-shaped, and in L. nitens they are hollow and rod- as well as platelet-shaped. We analyzed the coloration of the feathers by applying imaging scatterometry, bifurcated-probe- and micro-spectrophotometry. The reflectance spectra of the feathers of the European starling showed multiple peaks and a distinct, single peak for the Cape starling feathers. Assuming that the barbules of the two starling species contain a simple multilayer, consisting locally only of a cortex plus a single layer of melanosomes, we interpret the experimental data by applying effective-medium-multilayer modeling. The optical modeling provides quantitative insight into the function of the keratin cortex thickness, being the principal factor to determine the peak wavelength of the reflectance bands; the melanosome layer only plays a minor role. The air cavity in the hollow melanosomes of the Cape starling creates a strongly enhanced refractive index contrast, thus very effectively causing a high reflectance.