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As natural predators, owls fly with astonishing stealth due to the serrated feather morphology that produces advantageous flow characteristics. Traditionally, these serrations are tailored for airfoil edges with simple two-dimensional patterns, limiting their effect on noise reduction while negotiating tradeoffs in aerodynamic performance. Conversely, the intricately structured wings of cicadas have evolved for effective flapping, presenting a potential blueprint for alleviating these aerodynamic limitations. In this study, we formulate a synergistic design strategy that harmonizes noise suppression with aerodynamic efficiency by integrating the geometrical attributes of owl feathers and cicada forewings, culminating in a three-dimensional sinusoidal serration propeller topology that facilitates both silent and efficient flight. Experimental results show that our design yields a reduction in overall sound pressure levels by up to 5.5 dB and an increase in propulsive efficiency by over 20% compared to the current industry benchmark. Computational fluid dynamics simulations validate the efficacy of the bioinspired design in augmenting surface vorticity and suppressing noise generation across various flow regimes. This topology can advance the multifunctionality of aerodynamic surfaces for the development of quieter and more energy-saving aerial vehicles.

BACKGROUND: The chicken body louse is an obligate ectoparasite of domestic chickens. Chicken body lice feed on feathers, and infestation with this louse is linked to decreases in egg production, hen weight, and feed conversion efficiency. However, it is unknown how chicken body lice impact egg-laying chickens in cage-free environments. Welfare and behavior metrics were collected from flocks of egg-laying chickens either infested with chicken body lice or left uninfested. METHODS: In two trials, two flocks of cage-free commercial egg-laying chickens were infested with chicken body lice or maintained as uninfested controls. At three timepoints, behavior and welfare of all chickens was measured. On-animal sensors were used to quantify pecking, preening, and dustbathing behavior. Other animal-based welfare metrics included recording comb wounds and skin lesions. RESULTS: Birds infested with chicken body lice exhibited significantly more preening behaviors than uninfested birds, even at low louse levels. Moderate or severe skin lesions were detected on birds that were moderately infested with chicken body lice while skin lesions were never detected on uninfested birds. CONCLUSIONS: The welfare of chickens was impacted by the chicken body louse, a chewing louse that primarily feather feeds. Evidence of skin lesions on infested birds suggests that lice may cause more damage to birds than previously thought, and further evaluation of louse economic damage is necessary.

Individual organisms can function as ecosystems inhabited by symbionts. Symbionts may interact with each other in ways that subsequently influence their hosts positively or negatively, although the details of how these interactions operate collectively are usually not well understood. Vane‐dwelling feather mites are common ectosymbionts of birds and are proposed to confer benefits to hosts by consuming feather‐degrading microbes. However, it is unknown whether these mites exhibit generalist or selective diets, or how their dietary selection could potentially impact their symbiotic functional nature. In this study, we conducted 16S rDNA and ITS1 amplicon sequencing to examine the microbial diet of feather mites. We characterized and compared the diversity and composition of bacteria and fungi in the bodies of mites living on feathers of the Prothonotary Warbler, Protonotaria citrea, to microbial assemblages present on the same feathers. We found less diverse, more compositionally similar microbial assemblages within mites than on feathers. We also found that mites were resource‐selective. Based on the identity and known functions of microbes found within and presumably preferred by mites, our results suggest that these mites selectively consume feather‐degrading microbes. Therefore, our results support the proposition that mites confer benefits to their hosts. This study provides insight into symbioses operating at multiple biological levels, highlights the ecological and evolutionary importance of the synergistic interactions between species, and greatly expands our understanding of feather mite biology. [ABSTRACT FROM AUTHOR]

For the welfare assessment on commercial broiler and turkey farms, not only the recording of animal-based indicators but also the evaluation of the resulting prevalence or rate is essential. Two evaluation methods were compared using data on welfare indicators collected over 1 year from 11 broiler and 11 turkey farms in Germany: the application of normative values from an evaluation framework and the calculation of a benchmark. The evaluation framework had recently been developed in a participatory process that provided an evaluation with target and alarm values. The target range was predominantly based on ethical considerations, while the alarm range was aligned with the current status quo from farm investigations. The 25th percentile and the 75th percentile of the benchmarking were similarly classified as target and alarm. When applying the evaluation framework across all indicators and flocks, 30.6% of broiler flocks were in the target range, while 41.4% were in the alarm range, mostly for indicators such as footpad dermatitis, weight uniformity, and mortality. For turkeys at week 5 or at the end of the fattening period, 51.6% and 32.9%, respectively, were in the target range and 12.3% and 14.4% were in the alarm range. Most alarm classifications were related to footpad dermatitis, low-weight uniformity, plumage damage, and skin injuries. The application of normative values led to a significantly worse average welfare rank over all indicators and flocks for broilers compared to the benchmark, while no difference was observed for turkeys. The farm selection process may have favored turkey farms with better management practices, resulting in a more rigorous benchmark than in broilers. In addition, the farm data used to set the normative values had indicated a poorer status quo in turkeys for certain indicators, resulting in less stringent limits for the alarm range. This highlights the challenges associated with both evaluation methods: normative values are affected by the process and criteria used to set them, while benchmarks are affected by the reference population, which calls for large databases with regular updates. Also, for normative values, developments in the sector and the latest scientific evidence should be used for recurrent validation. [ABSTRACT FROM AUTHOR]

Multiple rows of feathers, known as the covert feathers, contour the upper and lower surfaces of bird wings. These feathers have been observed to deploy passively during high angle of attack maneuvers and are suggested to play an aerodynamic role. However, there have been limited attempts to capture their underlying flow physics or assess the function of multiple covert rows. Here, we first identify two flow control mechanisms associated with a single covert-inspired flap and their location sensitivity: a pressure dam mechanism and a previously unidentified shear layer interaction mechanism. We then investigate the additivity of these mechanisms by deploying multiple rows of flaps. We find that aerodynamic benefits conferred by the shear layer interaction are additive, whereas benefits conferred by the pressure dam effect are not. Nevertheless, both mechanisms can be exploited simultaneously to maximize aerodynamic benefits and mitigate stall. In addition to wind tunnel experiments, we implement multiple rows of covert-inspired flaps on a bird-scale remote-controlled aircraft. Flight tests reveal passive deployment trends similar to those observed in bird flight and comparable aerodynamic benefits to wind tunnel experiments. These results indicate that we can enhance aircraft controllability using covert-inspired flaps and form insights into the aerodynamic role of covert feathers in avian flight. [ABSTRACT FROM AUTHOR]

Feathers are complex integument structures that provide birds with many functions. They are vital to a bird's survival, fundamental to their visual displays, and responsible for the evolutionary radiation of the avian class. Feathers provide a protective barrier for the body; their water repellency is a key feature. Despite hundreds of years of ornithological research, the available literature on how feathers repel water is both limited and puzzling. Most hypotheses from the early 1900s suggested uropygial gland oil provided feathers with a hydrophobic coating. Subsequent studies showed that the feather's hierarchical structure creates a porous substrate that readily repels water with or without oil. Numerous studies and methods have been published attempting to explain, quantify, and compare the water repellency of feathers. Many overlook the role of barbules and the effect of their variation, which both likely play a crucial part in water repellency. The goal of this paper is to synthesize this research to better understand what has been done, what makes sense, and more importantly, what is missing. Previous reviews on this subject are mostly over 30 years old and did not use modern methods for systematic review. Here, we performed a systematic review to capture all relevant published papers on feather water repellency. We emphasize the crucial role of barbules in feather water repellency and why their morphological variation should not be ignored. We answer the question, what do we really know about the water repellency of feathers? [ABSTRACT FROM AUTHOR]

A 50‐day feeding trial was conducted to evaluate the effects of mulberry leaf powder water extract (MLE) on the growth performance, immunity, antioxidant, meat quality and intestinal microbiota of yellow feather broilers. A total of 720 birds (initial body weight 40.07 ± 0.05 g) were randomly distributed into four groups with six replicates per group and 30 birds per replicate. Four diets were formulated with 0% (CON), 200 mg/kg MLE (MLE200), 400 mg/kg MLE (MLE400) and 600 mg/kg MLE (MLE600) supplementation. Results showed that the addition of 200–600 mg/kg MLE to the diet significantly increased the body weight (BW) and average daily weight gain (ADG), but feed to gain ratio (F/G) were linearly decreased (p = 0.045) as dietary MLE increased. Birds fed MLE400 had higher (p < 0.05) total antioxidant capacity (T‐AOC), interleukin‐10 (Il‐10), secretory immunoglobulin A (SIgA) and complement 3 (C3) contents than those fed CON, whereas MLE400 had lower malondialdehyde (MDA) content than CON (p < 0.05). Analysis of 16 S rDNA indicated that supplementation with 200 mg/kg MLE increased the Shannon indices in the caecum (p < 0.05). Supplementation with MLE decreased the abundance of the phylum Proteobacteria and genus Helicobacter, and increased the abundance of the phylum Bacteroidetes in the caecum in broiler chickens (p < 0.05). The drip loss rate in the MLE600 was significantly diminished (p < 0.05), whereas the shear force was significantly elevated (p < 0.05). In summary, dietary supplementation with MLE can effectively improve growth performance, intestinal immunity, serum antioxidant capacity, meat quality and intestinal microbiota of yellow feather broilers. The most appropriate MLE supplementation level was 400 mg/kg. This study provides a practical strategy for the dietary application of MLE in yellow feather broilers. [ABSTRACT FROM AUTHOR]

This study investigates the use of planar wingtip attachments to improve the lift generating performance of low aspect ratio (AR) flat-plate wings in the low Reynolds number (Re) range (<105). Inspired by nature's solutions, the slotted wingtip feathers of high lift wings as seen in eagles, we tested different configurations of wingtip attachments, ranging from a base plate with no attachments to plates with one, two, or four attachments for Re=8×104−15×104. The lift-to-drag (L/D) ratio, a commonly used metric for gauging the aerodynamic performance, shows that the configuration with four attachments (4A) has the superior performance. In the case of ARs of 1.0 and 1.5, the 4A configuration returns an average improvement of 20% and 7% over the base plate, respectively. The Oswald's efficiency factor (e), calculated for the experimental cases, is varied from a low 0.24 to more typical values of 0.86. The force per unit volume parameter is used to compare the performances of the modified wings and to take into account the weight added by the attachments. The results obtained demonstrate that the 4A configuration offers superior performance compared to the weight gained because of the addition of the attachments. [ABSTRACT FROM AUTHOR]

Despite major implications, moult remains understudied compared with other major annual cycle phenomena such as breeding and migration. This is certainly true for Eurasian Spoonbills Platalea l. leucorodia for which even the primary moult has remained poorly described. Using digital photography, we studied primary moult of Spoonbills in the eastern Dutch Wadden Sea from July to October 2021. From the images that were sufficiently clear to quantify primary moult we obtained a total of 168 observations for immatures and 790 for adults. We aged spoonbills by the extent of black on the primary tips and scored their abdominal profile as an index of body mass. Progression of the descendent moult showed a distinct sigmoid pattern, implicating population turnover at the start and end of the study period. Also, few individuals completed moult in the study area. Therefore, we applied Underhill-Zucchini models to actively moulting individuals. As expected, immatures were estimated to initiate moult over a month earlier (11 June) than adults (20 July). Surprisingly, immature spoonbills moulted at a higher rate, which would allow immatures to complete primary moult in 131 days without suspension compared with 170 days in adults. As a fast moult may reduce feather quality, we speculate that the black wing tips of immature spoonbills may compensate for lower feather quality. Birds with low abdominal profile scores were observed only in July and August, but fat birds were seen throughout the study period. The incidence of suspended moult sharply increased through September in both age groups. By late September 30–40% of birds had suspended moult and abdominal profile scores peaked. This means that immature and adult spoonbills appear to synchronize the suspension of moult before migration, despite marked age differences in the onset and rate of primary moult. Spoonbills may benefit from synchronized migration by improving navigational accuracy and flight efficiency through collective decision-making and formation flights. [ABSTRACT FROM AUTHOR]

Lymphoma was diagnosed in two wild tawny frogmouths (Podargus strigoides) presented to the Australian Wildlife Health Centre, Healesville Sanctuary, Victoria. The first case presented with extensive feather loss refractory to treatment. Bacterial and fungal folliculitis and beak and feather disease virus were excluded as primary causes, and the bird was euthanised due to poor response to treatment. Histopathological examination of the skin showed an extensive infiltrate of pleomorphic mononuclear leucocytes, suggestive of cutaneous lymphoma. Immunohistochemistry revealed >95% of these cells were CD3 positive, consistent with T cell lymphoma. The second case presented debilitated and in poor body condition and was euthanised due to poor prognosis. Histopathological examination revealed extensive infiltrates of pleomorphic mononuclear leucocytes in multiple tissues, suggestive of disseminated lymphoma. Immunohistochemistry revealed 70%–80% of these leucocytes were Pax5 positive, consistent with a B cell lymphoma. To the authors' knowledge these cases constitute the first report of malignant neoplasms in members of the Order Caprimulgiformes. Cutaneous lymphoma should be considered as a potential differential diagnosis for severe feather loss in tawny frogmouths and other avian species, when other more common causes have been ruled out. Similarly, disseminated lymphoma is a differential diagnosis worthy of consideration in cases of systemic debilitation in tawny frogmouths. [ABSTRACT FROM AUTHOR]

In recent decades, the compositions of preen oil and feathers have been studied to achieve insights into the chemistry of avian odours, which play a significant role in birds' social behaviour. Fewer studies are available regarding volatiles originating from other sources, such as faeces, eggs or a bird's whole body. The aims of this study were (i) to identify odour-active and further volatile compounds in zebra finch whole body odour and (ii) to semi-quantify selected volatiles and use the information to evaluate two different adsorbents for their suitability for whole body odour sampling. Volatiles from the headspace above zebra finches were sampled using an open loop system equipped with either activated charcoal or Tenax® TA. Samples were analysed by olfactory-guided approaches as well as gas chromatography–mass spectrometry. Using activated charcoal as sorbent, 26 odour-active and 73 further volatile compounds were detected, whereas with Tenax® TA 27 odour-active and 81 further volatile compounds were detected. In total, 104 compounds were (tentatively) identified, of which 22 had not been identified previously in zebra finch odour and 12 had not been described in any birds. Hints towards a chemical sex signature became evident for qualitative but not for quantitative differences. With the exception of some compounds, notably carboxylic acids and alkanes, relative peak areas obtained with the two adsorbent types were comparable. The approach described herein is proposed for future studies aiming to determine volatiles emitted by birds when, for example, parent birds are approaching the nest. [ABSTRACT FROM AUTHOR]

Simple Summary: Feather mites are a specific group of ectoparasites or commensals of almost all bird species worldwide, morphologically and biologically adapted to function in a very unusual environment—the plumage of their hosts. They are able to attach themselves so strongly to feathers that they do not leave their hosts even after their death, remaining on or in the feathers as dried 'mummies'. This makes it possible to discover and describe them by viewing birds preserved in museum collections. Of the currently known approximately 2500 species of feather mites, the vast majority are derived from just such a source of material. Also, the species described in this paper, new to knowledge, Grallolichus heliornisi sp. n. (Pterolichidae), comes from an old exhibition specimen of the sungrebe (Heliornis fulica) from the family finfoots (Heliornithidae), found in the collection of the Zoological Museum in Kiel (Germany). This is the first record of a representative of this genus on finfoots and the first description of a new species for Grallolichus in more than 50 years. The diagnosis of the new species is based on a detailed analysis of the morphology, complemented by a key to the species known so far, and summarized through a reflection on the importance of old ornithological collections for understanding the biodiversity and evolution of feather mites. Feather mites of finfoots (Heliornithidae), a small gruiform family, are poorly and partly erroneously recognized. Grallolichus heliornisi sp. n. (Astigmata: Pterolichidae) is here described from the sungrebe Heliornis fulica as the first representative of the genus commonly found on close relatives of finfoots, Rallidae and Sarothuridae. This species belongs to the species group having ornamented dorsal shields and is morphologically most close to G. proctogamus inhabiting Eurasian coot (Fulica atra). Males of the new species differ from G. proctogamus mainly by the shape of opisthosomal lobes (triangular vs. rounded) and the aedeagus form (parallel sided vs. tapering distally). Females differ mainly by the shape of supranal concavity (open anteriorly vs. closed) and location of setae h1 in relation to supranal concavity (lateral vs. anterior). A key to known species of the genus Grallolichus is provided. The morphological analysis and descriptive characterization of this species, like much of the approximately 2500 feather mite species described to date, were based on mummified mite material preserved in 19th-century old museum bird specimens. These often-forgotten collections are the only source for the analysis of the acarofauna of many rare, unavailable wild or even extinct bird taxa. [ABSTRACT FROM AUTHOR]

Meat goose can represent one of the most significant economic waterfowl in China. An excessively high stocking density can reduce the production performance and welfare of geese. Moreover, the light-emitting diode (LED) green light can play a pivotal role in regulating the growth and development of embryos and offspring in chickens. This study aims to determine the optimal regimen of LED green light in the high-density rearing mode of goslings. According to the actual production, a two-factor experiment was designed with the incubation light (dark and LED green) and growth light (LED white and LED green). A systematic analysis was made to explore the effects of LED green light on growth performance, intestinal development, blood hormones, feather quality, and pecking behaviors of geese in high-stocking density. The results show that the light intensities were 30–40 and 30–35 lx during the incubation and brooding period, respectively, with a light cycle of L:D = 24:0. The growth performance of geese was significantly improved by LED green light during the gosling brooding period. The LED green light during the growing period was found to significantly increase the body weight of geese at 14 days, as well as the daily gain and feed intake of geese for 1 to 14 days (P < 0.05). Furthermore, there was a significant decrease in the ratio of feed to gain of geese for 1 to 14 days (P < 0.05). A significant reduction was found in the concentration of serotonin and corticosterone in the blood, as well as the duodenal crypt depth of the geese at 14 days in the green light group during the growth period (P < 0.05), compared with the white light group. Furthermore, the LED green light irradiation during the growing period was observed to significantly increase the length of the chest and abdomen feathers of geese at 14 days post-hatching (P < 0.05), whereas, the back bare score of geese was reduced at 14 days post-hatching (P < 0.01), and the average pecking time and frequency of geese was reduced for 1 to 14 days post-hatching (P < 0.001). Thus, the green light environment during the growing period was significantly beneficial to the quality of the feathers and the development of geese plumage. The LED green light during the embryonic period was found to significantly reduce the average pecking time and frequency (P < 0.05) for better feather pecking behavior in geese. Moreover, the hatching procedure of green light outstandingly reduced the duodenal crypt depth (P < 0.01), where there was an increase in the jejunal villus height of geese at 14 days (P < 0.05), compared with the control group. The adverse effects of intensive farming were reduced on the intestinal development of geese. Moreover, there was no significant interaction to identify between the incubation and brood lights, in terms of the regulation of growth performance, intestinal development, blood hormones, feather quality (feather length, cleanliness, and damage degree), and feather pecking behavior of geese. Therefore, the LED green light shared the positive regulations on the negative effects of high-density rearing of goslings. Moreover, the LED green light during the growing period of goslings yielded superior outcomes. It is thus recommended that green light irradiation can be employed at the brood stage of goslings in actual production, in order to mitigate the adverse effects of modern intensive farming on goslings. The findings can provide a theoretical basis for the efficient production of geese. [ABSTRACT FROM AUTHOR]

Most animals live and move in a landscape in which the risk of predation varies spatially and temporally, that is, a "landscape of fear" which may strongly affect their ecology and behaviour. Cavity‐nesting birds prospecting for nest sites are often forced to investigate unfamiliar, dark holes that may be dangerous to enter because they may conceal an aggressive nesting bird or a predator. The Fear of Feathers Hypothesis posits that some birds such as blue tits Cyanistes caeruleus, add large, conspicuous feathers on top of their own nest to exploit the fear of potential nest usurpers or brood parasites. Feathers may trigger fear in prospecting birds either because the feathers obstruct the view of the cavity interior, and/or because the feathers may be perceived as recent prey remains and suggest the predator will return. Here I studied the prospecting behaviour of unmated male pied flycatchers Ficedula hypoleuca by letting them choose between a dyad of nest boxes where one contained a nest of a great tit Parus major and one a nest of a blue tit. The objective was to test whether the presence of feathers would have a stronger repelling effect than the species that had built the nest. Great tits are larger than blue tits and may represent a greater threat to intruding flycatchers. However, blue tits but not great tits, often decorate their nest with large, conspicuous feathers. Consistent with the Fear of Feathers Hypothesis, flycatchers hesitated longer to enter blue tit than great tit nests but only if the blue tit nest contained feathers. The study has relevance to many species of birds that decorate their nest with feathers. It shows that a landscape may include aspects of fear that are important to animal behaviour although they may seem subtle and are easily overlooked. [ABSTRACT FROM AUTHOR]

The 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. [ABSTRACT FROM AUTHOR]

Trait polymorphisms are a perennially popular topic of study in ecology and evolutionary biology. Plumage polymorphisms occur broadly in birds, with a particularly high rate among the raptors. The regularity of this heritable, melanin-based trait in raptors has prompted research into its potential connections to aspects of life history such as immune response, foraging ecology, and mating systems. Because raptors are a non-monophyletic grouping of multiple orders, they can further be leveraged to explore the eco-evolutionary drivers of recurrent plumage polymorphism phenotypes. Here we characterize plumage polymorphism throughout the raptors and review the existing literature on factors involved in its development and maintenance. We identify patterns and trends in this past body of research and discuss the opportunity to strengthen our understanding of plumage polymorphism through a holistic research approach. Specifically, we detail the likely benefits of applying genomic tools to plumage polymorphism research in raptors while encouraging both a focus on unstudied polymorphic species and on the potential interactions among multiple hypotheses that might promote plumage polymorphism. [ABSTRACT FROM AUTHOR]

Owls make almost no noise when gliding, thanks to the unique feather structure at the tail of their wings. Drawing on the tail structure of the owl wings, the trailing edge of the duct in the pump-jet propulsor (PJP) system is improved. Based on the detached eddy simulation method, the influence of serrated trailing edge on the pulsating pressure and noise performance of a PJP under submarine self-propulsion conditions is numerically analyzed. The results show that the influence of the serrated trailing edge on the self-propulsion performance is negligible. The serrated trailing edge destroys the large-scale duct-induced vortices in the spanwise direction, and additional secondary vortices are formed in the wakefield, increasing the pulsating pressure of the downstream flow field. The pulsation amplitude of each order at the downstream monitoring point of the serrated duct PJP (SD-PJP) model is significantly greater than that of the benchmark PJP (BM-PJP) model. The serrated trailing edge can effectively reduce the noise of PJP. The maximum noise reduction in the axial and radial planes is 1.23 and 0.91 dB. [ABSTRACT FROM AUTHOR]

Simple Summary: This study describes how in 30 post-hatching days, captive barn owl chicks undergo postural changes, starting from a condensed egg posture in which their relatively big head is bent underneath the trunk, and culminating in the upright posture of adult owls. Interestingly, during the first 10 post-hatching days, while their eyes are still closed, their activity increases, following a mobility gradient that starts with lateral head movements that are followed by pivoting around the hindquarters, and then by shifting to forward progression. This gradient was previously described in the development of rat pups and in other mammals when they switch from immobility to activity. Once the eyes are opened, activity decreases and the chicks are mostly stationary, preoccupied with lateral and peering head movements, scanning the environment. The latter behavior is typical of adult owls when not on the wing. The chicks start flying on day 50, first by swooping down when placed on a perch and then actively flying in the aviary. Altogether, the development of movement in barn owls first demonstrates a conspicuous resemblance with a general mobility gradient and then speciation from that general developmental pattern to the typical barn owl behavior. Hatching captive barn owl chicks underwent four developmental phases. In the first 10 days (phase 1), behavior consisted of lateral movements that gradually changed to forward progression and peaked a few days before and after eye-opening. This behavior resembled a general developmental pattern that characterizes other vertebrates. Chicks also underwent a postural change, from head bent underneath the ventrum to resting on the rear end of the trunk with the head lifted in the air. Then, once their eyes were opened, chicks became more stationary and preoccupied with visual exploration, manifested in lateral head movements and peering episodes (phase 2, until day 20). The latter behavior, which is also typical of mature owls when not on the wing, characterized the chicks' behavior after post-hatching day 20 (phase 3), when their flight and contour feathers grew, along with shedding the down plumage and standing tall. Development culminated in active flight, first observed by days 50–60 (phase 4). Altogether, during post-hatching development, barn owl chicks gradually shifted from egg posture to the adult upright body posture. At the same time, their behavior consisted of speciation from the general developmental pattern to the typical stationary barn owl behavior, and, finally, flight was incorporated. [ABSTRACT FROM AUTHOR]

Birds have traits that can induce better aerodynamic efficiency along with high manoeuvring capability during its flight, which could be shared with unmanned aerial vehicles for improving their aerodynamic performances. One such feature of the wing tip, i.e. the primary feathers of the birds could be an effective geometrical feature to reduce the wing tip vortices. This paper presents the bio-inspired wing tip devices, i.e. three-and four-tipped multiple winglets in reducing the strength of vortices emanating from the wing tip of the wing operating in the Reynolds number (Re) of 0. 9 7 9 4 × 1 0 5 and 0. 9 7 9 4 × 1 0 6 . Different combinations of both three- and four-tipped multiple winglets have been designed by varying the cant angle of each tip. Numerical simulations were carried out using Ansys-Fluent by solving three-dimensional Reynolds averaged Navier–Stokes formulations coupled with k- ϵ turbulence model to resolve the features of tip vortices. The simulation clearly indicates that there is a strong correlation between the size of the vortices and the aerodynamic performance parameters such as C L / C D , (C L) max ,   C L 0. 5 / C D , C L 1. 5 / C D . The three- and four-tipped multiple winglets are effective in reducing vortex drag by disintegrating large strength vortex which occurs in the tip of straight wing, into few numbers of small strength vortices. When compared to straight wing, three-tipped multiple winglet with the cant angle combination of 50, 30, 10 improves the aerodynamic efficiency by 22% to 23% and the four-tipped winglet with the cant angle combination of 60, 50, 40, 30 enhances the same by 21% to 22% in the Re of 0. 9 7 9 4 × 1 0 5 . Even the longitudinal static stability has seen considerable improvement for four-tipped multiple winglets than three-tipped multiple winglets and straight wing. [ABSTRACT FROM AUTHOR]

The mountain hawk-eagle has a special status among the indigenous Paiwan people of Taiwan. This article examines the historical evolution of the use of this eagle’s feathers amid social transformations within Paiwan culture. It also addresses the bird’s endangered status and proposed conservation strategies to protect it. Wildlife management collaborations between indigenous communities and conservationists have sparked conflicts in values and worldviews that are challenging to reconcile. While the Paiwan wish to continue using the eagle’s feathers in important cultural rituals, this increased demand exacerbates hunting pressures on the species. This article seeks to find a better balance between preserving cultural practices and ensuring species survival. Drawing on four years of fieldwork among the Paiwan, it demonstrates the complexities of navigating entangled human–animal relationships in the context of species endangerment. [ABSTRACT FROM AUTHOR]

The mechanisms regulating plumage coloration appear to be phylogenetically conserved in avian species: the plesiomorphic character state is estrogen-dependent regulation, while testosterone, luteinizing hormone, and non-hormonal control are derived states. Limited data exist on the underlying regulatory processes of sexual dichromatism in the Eared Dove (Zenaida auriculata (Des Murs, 1847)). Since the Columbiformes order is close to basal branches, we hypothesized that estrogen and testosterone play a central role in the regulation of crown plumage coloration in the Eared Dove. To test this, we subjected adult males to a forced molt accompanied by an exogenous increase of estradiol and testosterone to determine whether the presence of these hormones during molting modified the spectrophotometric characteristics of the plumage. No significant differences were found between treatments and controls in the colorimetric variables hue, ultraviolet saturation, and brightness. Similarly, the avian visual model showed no perceptible changes in chromatic and achromatic signals in the individual male adults. We also analyzed the effects of estrogen and testosterone on the growth speed of the new feathers. The hormone-treated groups increased in the speed of molting compared to the control group. These results suggest that the Eared Dove is an exception to basal branch models: rather than regulating coloration, sex hormones speed up the growth of the new feathers. [ABSTRACT FROM AUTHOR]

We analysed primary and secondary feather moult and fat reserves in 539 Common Snipes captured in the middle Pripyat River Valley, an important stopover site for waders in Central Europe, between 2002 and 2022. The average daily rate of feather growth was 1.89% in primaries and 2.27% in secondaries, being one of the highest documented in waders. The estimated duration of growth for a single flight feather varied from 11 to 21 days in primaries and from 8 to 11 days in secondaries. Moreover, multiple flight feathers (up to 14) were replaced simultaneously. As a result, the wing moult in Common Snipes was rapid with the mean primary moult duration estimated at 53 days (28 June–20 August) according to the Underhill–Zucchini model, and only 20 days in secondaries (31 July–20 August) based on moult estimates of individual secondaries. Hence, although secondary feathers began to grow when primary moult was already advanced, moulting of both flight feather groups was completed in most birds at almost the same time. Our study shows that Common Snipe in the middle Pripyat River Valley exhibit very rapid wing moult with large wing gaps. Fat reserves and thus body mass of Common Snipes were the lowest when the wing gap was greatest, compensating for their reduced wing area. Late and slow movement towards wintering grounds, allows them to moult rapidly at the early stage of autumn migration, which is likely to occur only in sites with abundant food resources. [ABSTRACT FROM AUTHOR]

Many empirical studies have focused on highly ornamented species to identify ecological factors that maintain the ornamentation or favour its exaggeration. By contrast, although reduction or loss of ornamentation appears to be widespread, species with reduced/lost ornamentation and its relationship with ecological factors are rarely focused on. Here, based on data collected over 4 years, we studied outermost tail feather length, i.e. a well-known sexual ornamentation in this clade, in relation to roosting location in the Pacific Swallow Hirundo tahitica during winter. In contrast to congeners, this species has inconspicuous tail ornamentation, i.e. very shallowly forked tails with vestigial streamers, providing a rare opportunity to study the ecological factors driving reduced ornamentation. We found that Pacific Swallows mainly roost in old nests under bridges over rivers, which resemble their original roosting sites, but some roost in much warmer sites, i.e. old nests under the eaves of houses above the ground. Individuals roosting under the eaves of houses had significantly longer outermost (but not central) tail feathers than those roosting under bridges. Individuals roosting under the eaves of houses were heavier and showed lower physiological stress, and thus might better endure the maintenance cost, favouring ornament elaboration. Because we controlled for the effects of sex and age, these factors would not confound the observed pattern. Reduced ornamentation, as found in Pacific Swallows roosting under their original roosting sites, could become elaborated in benign environments (i.e. under eaves, here), stressing the importance of balance between the costs and benefits of ornamentation. [ABSTRACT FROM AUTHOR]

Microbes within a consortium exhibit a synergistic interaction, enhancing their collective capacity to perform functions more effectively than a single species, especially in the degradation of keratin-rich substrates. To achieve a more stable and efficient breakdown of chicken feathers, a comprehensive screening of over 9,000 microbial strains was undertaken. This meticulous selection process identified strains with the capability to degrade keratin effectively. Subsequently, antagonistic tests were conducted to isolate strains of fungi and bacteria that were non-antagonistic, which were then used to form the artificial microbial consortia. The optimal fermentation conditions for the keratinophilic microbial consortia were determined through the optimization of response surface methodology. The results revealed that 11 microbial strains–comprising of 4 fungi and 7 bacteria–were particularly proficient in degrading chicken feathers. The artificially constructed microbial consortia (AMC) comprised two bacterial strains and one fungal strain. The optimal conditions for feathers degradation were identified as a 10 g/L concentration of chicken feathers, a 2.6% microbial inoculation volume and a fermentation fluid pH of 9. Under these conditions, the degradation rate for chicken feathers reached a significant 74.02%, representing an 11.45% increase over the pre-optimization rate. The AMC developed in this study demonstrates the potential for efficient and economical process of livestock and poultry feathers. It provides innovative insights and a theoretical foundation for tackling the challenging degradation of keratin-rich materials. Furthermore, this research lays the groundwork for the separation and purification of keratins, as well as the development of novel proteases, which could have profound implications for a range of applications. [ABSTRACT FROM AUTHOR]

We used light and raster electron microscopy to study for the first time in research the microstructure of the down parts of feather vanes consisting of combined barbules ("barbule I") provided with both typical plumulaceous barbules ("barbicel," "barbule II") and modified plumulaceous barbules (MBs). Their presence and distribution over different pterylae were studied on 3330 feathers from 441 birds of 129 species belonging to 45 families of 19 orders. Information about the presence of afterfeathers and of umbilical barbs on feathers was clarified. Modified plumulaceous barbules were found on feathers of all species studied, more often on coverts, less often on wing and tail feathers. Down components were studied in most detail in the orders Charadriiformes and Passeriformes; in the former, the presence or absence of MB was specific at the level of family or genus, while in the latter, afterfeathers or umbilical barbs were never found together on the same feather. The possibility is discussed of using various combinations of down components and features of their microstructure as an important addition to the integrated system of ptilological taxa identification by feathers (including single feathers) and in some cases even by the pteryla to which the tested feather belongs. [ABSTRACT FROM AUTHOR]

This article explores the impact of ectoparasitic mites on cage-free egg production in the United States and strategies for managing these mites. The transition to cage-free housing has resulted in an increase in mite infestations, which negatively affect the health, behavior, and productivity of hens. The article discusses the genetic variability for mite resistance and the potential use of genomic selection to improve mite resistance in poultry populations. It also provides information on the biology of the northern fowl mite and poultry red mite, as well as various management strategies, including the use of pesticides and biosecurity measures. The authors stress the importance of monitoring and managing mite infestations in egg production and call for further research to develop effective and sustainable strategies for improving hen welfare. They suggest that genomic selection could be a promising approach for breeding mite-resistant poultry strains. [Extracted from the article]

Migratory waterfowl are a harvested resource shared among multiple European countries, exposing them to potential overexploitation. Management of take is challenging since the life cycle of migratory waterfowl consists of several stages distributed among several locations, with possible spatio-temporal overlap among populations with differing population trends. Successful harvest management in such situations requires knowledge about the connections between breeding and non-breeding locations, and where birds are harvested. Breeding populations of Eurasian wigeon (Mareca penelope) are declining in Finland, underlining the need for more effective harvest management. Relative proportions and temporal distribution of local breeding birds and migrants from a larger Russian breeding population within the Finnish hunting bag has been unknown to date. We studied spatio-temporal origins of Finnish harvested wigeon by measuring stable-hydrogen (δ2H) isotope values from legally harvested birds. We modelled the changes in δ2H values of the feather samples within the hunting season using Gaussian processes and found that the origin of harvested wigeon in Finland changed during the hunting season and differed by age and sex. In juveniles and adult females but not in adult males, origin of harvested birds shifted from local and possibly western Russian birds to more long-distance migratory birds during the harvest season. These patterns likely reflected sex- and age-specific differences in migratory behaviour of Eurasian wigeon in the East Atlantic flyway, which can be used to guide future management and conservation of this species through the implementation of spatio-temporal harvest regulation. [ABSTRACT FROM AUTHOR]

The study explored the feasibility of producing protein feed by microbial enzyme synergy fermentation of feather meal and to determine the process parameters for this production. The keratin-degrading bacterial strains selected from the laboratory were combined with commercially available keratinase enzyme preparations to utilize microbial enzyme synergy in solid-state fermentation of feather meal. The in vitro pepsin digestibility was used as the index to analyze the fermentation time, inoculation amount, microbial enzyme ratio, and water addition through single-factor and orthogonal test analysis. The results showed that the optimal fermentation process was obtained: The water addition to feather meal was 45%, the microbial enzyme ratio was 1:1, the inoculation amount was 6%, and the fermentation time was 7 days. After fermentation, the in vitro pepsin digestibility of feather meal was 63.97%, which was significantly improved by 15.22% compared to before fermentation (P<0.01), and the soluble protein content was 3.51 g/L, which was significantly increased by 80% compared to before fermentation (P<0.05). The study indicates that under the optimal process parameters, using microbial enzyme synergy in solid-state fermentation of feather meal can efficiently produce protein feed and enhance the feed value of feather meal. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We present the results of an interdisciplinary study conducted at the Pedernales-5 site, situated in the Salar de Pedernales basin (26°S; 3356 masl), dated from 10,510−10,749 to 11,201−11,612 cal. BP. Unlike other Late Pleistocene and Holocene sites in the Andean Puna, where vicuñas (Vicugna vicugna) were the primary prey, at Pedernales-5, the zooarcheological assemblage consists almost exclusively of flamingo (Phoenicopteridae) and bird remains. Through the analysis of lithic and bone artifacts, archeobotanical remains, pigment composition, and paleoenvironmental data, we propose that the emphasis on flamingo exploitation cannot be solely explained by alimentary consumption but also served cultural and symbolic purposes related to the acquisition of feathers, hides, and bones. The unique archeological context of Pedernales-5 offers a distinctive perspective on human dynamics in the Andean highlands during the Early Holocene. [ABSTRACT FROM AUTHOR]

Today, more than ever, there is a need to uncover the patterns of thinking that shape the rationality of the leader cohort to aid them in their role-making of the challenging niche truly. This Husserlian phenomenological inquiry purported to explore the individual and collective lived experiences of nine (9) purposively selected Filipino academic managers regarding the essence of Dweck's growth and fixed mindsets in their leadership preparation. A semi-structured interview was employed as the main data gathering tool. Field texts were analyzed using Colaizzi's Procedural Steps to abstract the phenomenon's essence and were validated through the member checking procedure and critical friend technique. Interestingly, the study debuts an insightful Taxonomy of Cognitive Personas, which typifies the dynamic nature of the leader cohort's mindsets. Embedded in the Perennial Learner, Proactive Player, and Pragmatic Leader personas are cognitive tools and value priorities utilized in various influencing and regulating experiences in academic organizations. Academic organizations can use the findings of this study to focus on the cognitive preparation of millennial managers for higher leadership roles. Such findings are expected to complement the skill-based preparation that the millennials can employ for their role-making efforts in school leadership. [ABSTRACT FROM AUTHOR]

Woodstars are a clade of small hummingbirds with poorly known life history. One reason why they are insufficiently characterized is they tend to be little represented in museum collections. The Cornell Lab of Ornithology's Macaulay Library, an online database of user-uploaded photographs, is a complementary source of phenological information. Here, stimulated by our own field observations, we analyzed up to 200 photos per species from the Macaulay Library to investigate whether adult male Slender-tailed Woodstar (Chaetocercus [Microstilbon] burmeisteri), Amethyst Woodstar (Calliphlox amethystina), Chilean Woodstar (Eulidia yarrellii), Peruvian Sheartail (Thaumastura cora), and Purple-collared Woodstar (Thaumastura [Myrtis] fanny) molt into a drab-throated, nonbreeding plumage distinct from the better known iridescent-throated breeding plumage. We investigated these 5 species because adult males have elongated, dimorphic tails, meaning that we could distinguish adult males from immature males by their tail morphology alone. The photos show that, post-breeding, entire populations of Slender-tailed Woodstar and Peruvian Sheartail males replace their iridescent throat feathers with non-iridescent feathers, then molt back into their breeding plumage a few months later. The holotype of Microstilbon insperatusTodd 1913, type species of the genus Microstilbon, is an adult male of Slender-tailed Woodstar in the nonbreeding plumage that we describe here. Our data also suggest that male Amethyst, Chilean, and Purple-collared woodstars have a second distinct nonbreeding plumage. In these 3 species, photos showing the apparent drab-throated male plumage were rare, suggesting these species might have complex breeding phenology with some individuals molting into the nonbreeding plumage at the same time that others were breeding in iridescent-throated plumage. The rapidly growing number of photographs available in the Macaulay Library makes this resource valuable for documenting phenology, including for rare species such as woodstars. [ABSTRACT FROM AUTHOR]

In numerous animals, dramatic coloration (e.g. bright red or yellow) often indicates potential fitness, but it is less clear whether subtle coloration in the same individuals (e.g. grey or brown) could also encode such signals. To determine if subtle coloration could indicate health in a bird species with colorful feathers, house finches (Haemorhous mexicanus), we used spectrometry to objectively quantify leg brightness and saturation before, six days after, and 13 days after captive individuals were inoculated with a naturally‐occurring bacterial pathogen, Mycoplasma gallisepticum. We found that legs became less bright six days after infection (near the typical peak of infection), then more bright and less saturated at 13 days (entering the typical recovery period). These results suggest that subtle colors could reliably indicate current infection status, and therefore survival potential. [ABSTRACT FROM AUTHOR]

Birds are widely used as indicators of environmental contamination because they integrate signals across space and time. However, this advantage also means that locating the source of pollution can be challenging, especially for species that migrate large distances. Historically, the assignment of contaminant burden to particular life stages or locations has been made by sampling tissues with varying time signals and associating those signals with locations assigned from band recoveries or stable isotope analyses. Unfortunately, these assignments are geographically coarse. More recently, tracking devices have been increasingly used to determine more precisely where and when contamination is likely to occur. Here, we review current knowledge on using tracking devices to examine the relationship between avian movements and contaminant loads. We found 42 published articles with samples collected from 1986 to 2021 that used tracking devices to examine the relationship between avian movement and contaminant loads, where studies were primarily concentrated in the northern hemisphere, notably in the North Atlantic. Tracking methodology varied widely across studies to date, but the use of radiotransmitters and satellite tags generally decreased as newer technologies, such as global positioning systems and geolocation sensors, were developed. Blood and feathers were the most commonly used tissues to assess contaminant concentrations, but sample sizes were often low (<40, the recommended sample size for some tracking or contaminant studies), and one-quarter of studies did not statistically test the relationship between tracking data and contaminant concentrations. Moving forward, studies should (1) consider statistical power; (2) consider tissue turnover rates, contaminant turnover rates, and tracking device resolution; (3) examine tissues that inform different time scales; 4) explore the impacts of contaminants on behaviour and movement; and 5) increase collaboration, standardization, and information sharing across existing tracking or contaminant monitoring programs. Focusing on these aspects will enhance our ability to identify the source, transport, and fate of contaminants in avian species across the globe. [ABSTRACT FROM AUTHOR]

To explore potential factors contributing to high fluoroquinolone resistance levels, it is essential to develop analytical methods capable of detecting residues and trace amounts of antibiotic use in broilers. The aim of the present study was to develop and in-house validate a sensitive UHPLC-MS/MS method capable of determining enrofloxacin (ENR) and flumequine (FLU) residues at slaughter age (day 45) when the animals were treated with these antimicrobials one day after hatching. Residue depletion of ENR and FLU in feathers was also assessed. Two experimental trials were performed, both consisting of 5 different treatment groups. In the first trial animals were treated with ENR and in the second one with FLU. The developed method was successfully validated and was found to be sensitive enough to detect residues of fluoroquinolones in the feathers up until slaughter age in all treatment groups. Average ENR concentration on day 45 was 10 ng g−1 feather after drinking water treatment, with all concentrations above the limit of quantification (LOQ) of 5 ng g−1 feather. For FLU average concentration on day 45 after drinking water administration was 4 ng g−1 feather, with an LOQ of 1 ng g−1 feather. Therefore, the method is suited for application to monitor fluoroquinolone use in broilers. [ABSTRACT FROM AUTHOR]

1. The production of chicken meat has resulted in high volumes of byproducts, such as feathers, bones, skin, viscera, and feet. The structure of feathers is one of the most complex among vertebrates, with a central axis and lateral filamentary structures, providing rigidity, lightness, and flexibility. Chicken feathers are composed of proteins, lipids, and water, with the highest protein content, especially keratin, which is responsible for the material's rigidity. 2. Industries still make little use of feathers, which are generally intended for the production of flour or organic fertilisers. These are low added value products, and discarded feathers can harm the environment. 3. Keratin extraction techniques and resulting protein hydrolysates have been studied in chicken feathers. Acid, alkaline or enzymatic hydrolysis is the most commonly used method for obtaining molecules with functional properties such as antioxidant, antimicrobial, antihypertensive and antidiabetic activity. 4. The development of keratin-based biodegradable films represents an area of interest for reducing the economic and environmental impacts caused by inappropriate disposal of feathers. [ABSTRACT FROM AUTHOR]

Recordings from external and internal cameras in nest boxes provided insights into the breeding activities of two pairs of Common Swifts in the breeding season 2020 in Laufen (canton of Basel-Landschaft) in north-western Switzerland. It was possible to distinguish between the five adult birds present based on small features in their plumage or the presence of a ring, which allowed a detailed analysis of the birds' presence in the nest boxes and of their feeding behaviour. Both pairs successfully raised three young. On cool and rainy days, the adults stayed in the nest box longer in the morning or did not fly out at all, or only briefly. A total of eight approaches by a Common Kestrel triggered strong reactions from the breeding birds present: They stayed in the nest box significantly longer afterwards, before setting off on their next foraging flight, than when they flew in before or after the approach by a Kestrel. During the incubation period, both adults of a pair were present for similar lengths of time, and the feeding rate was also similar for males and females. Entries by other Common Swifts into unoccupied boxes were usually brief. In one of the two nest boxes equipped with a camera, a new male returned a few days earlier than the previous year's breeding pair and then displaced the previous year's male in a five-hour battle when the pair arrived. Together with the previous year's female, he then formed a pair and they began to breed together. However, in the middle of the breeding season, the previous year's male managed to take over the nest box and chase away the new male (the presumed father of the young). The young birds were between 10 and 12 days old at this time. For the next 10 days, the previous year's male initially did not participate in feeding the young. The female compensated for this by significantly increasing the number of feedings for several days. This suggests that it is possible for a single adult Common Swift to provide three young with sufficient food when the breeding partner is absent, at least in good weather conditions. [ABSTRACT FROM AUTHOR]

Extreme cold events, which have become more frequent, can revert the direction of long-term responses to climate change. In 2021, record snowstorms swept the United States, causing wildlife die-offs that may have been associated with rapid natural selection. Our objective was to determine whether the snowstorms caused natural selection in Eastern Bluebirds (Sialia sialis). To test which mechanism most influenced their survival, we measured the morphology and coloration of fatalities and survivors at three sites. Survival was associated with a longer tarsus and with a wider, longer, and deeper beak, in support of the starvation and thermal endurance hypotheses. Additionally, bluebirds with more-ornamented plumage were less likely to have survived, perhaps because of an early energy investment in mate and site acquisition. As bluebirds encounter increasingly warm summer conditions, the longer extremities favored during the snowstorms may continue to be favored through their thermoregulatory benefits. However, the dull plumage coloration favored by natural selection during the snowstorms may be opposed by sexual selection benefits of more-ornamented plumage. Overall, responses to extreme events are difficult to predict from responses to long-term climate change, and responses to one event, such as the 2021 snowstorms, may not predict responses to a future extreme event. [ABSTRACT FROM AUTHOR]