Individual Feathers Research Articles

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.

Intra‐ and interspecific variation in trace element concentrations in feathers of north European trans‐African migrants

The knowledge of migratory connectivity is important for understanding the potential drivers of populations and it is thus important for conservation implications. Migratory connectivity of species can be studied using exogenous, such as rings and transmitters, or endogenous markers, such as stable isotopes and trace elements. The use of trace elements has been much less frequently studied compared to stable isotopes. Trace elements can be studied from the feathers of birds and this does not necessarily require trapping of individuals. Here we studied the variation of 18 different trace elements in feathers of two long‐distance trans‐African migrants, willow warblers Phylloscopus trochilus and barn swallows Hirundo rustica, using body feathers of museum specimens of birds from Finnish breeding grounds. The trace elements were measured using laser‐ablation inductively‐coupled‐plasma mass‐spectrometry (LA‐ICP‐MS). We show that trace element concentrations were relatively stable along the rachis within the same feather except in Ni and S, which showed a quadratic pattern. In general, variation within feathers of the same individuals was smaller than in feathers between individuals for most elements. Furthermore, concentrations of 11 trace elements showed significantly higher concentrations in willow warbler feathers collected in spring than in autumn, moulted in African wintering grounds and European breeding grounds, respectively. Last, concentrations of seven trace elements were significantly higher in the spring feathers of willow warblers compared to barn swallows. This suggests that trace elements could be used to separate moulting grounds of the birds on the larger scale within the same species, but also sampling design should be carefully considered.

Seasonal changes in plumage density, plumage mass, and feather morphology in the world’s northernmost land bird, the Svalbard Rock Ptarmigan (Lagopus muta hyperborea)

The Svalbard Rock Ptarmigan, Lagopus muta hyperborea, is the only year-round resident terrestrial bird in the high Arctic. Many of the physiological and morphological adaptations permitting its winter endurance in this harsh environment are well understood. However, it remains unknown how the conspicuous moult from a greyish brown summer to a white winter plumage, and any underlying changes in plumage structure and feather morphology, contribute to seasonal acclimatisation. We used standard morphometric techniques to describe the seasonal change in plumage and feather characteristics in six body regions. Then, we investigated whether winter plumage traits differed between first-winter and adult (second winter, or older) birds, because a difference in coat insulation has been suggested as an explanation for why first-winter Svalbard Ptarmigan loose more heat than adults. Plumage feather density (i.e., feathers × cm−2) and mass density (i.e., mg feathers × cm−2) were higher in winter, particularly on the head and feet where individual feathers were also heavier, longer, and downier. Seasonal changes in other regions (back, tarsi) indicated acclimatisation primarily to resist physical wear and wind. First-winter and adult birds had similar feather densities. However, mass density in first-winter birds was significantly lower than in adults in all but one body region (back) because individual feathers weighed less. This can explain previous observations of higher heat loss rates in first-winter birds. Our study suggests that plumage acclimatisation contributes to optimising the winter phenotype of Svalbard Rock Ptarmigan, both through higher insulative capacity and by improved resistance to harsh weather. The extent of these adaptations may be determined by the time or energy available for feather growth, exemplified here by inferior insulation in first-winter birds.

Draft genome assemblies of the avian louse Brueelia nebulosa and its associates using long-read sequencing from an individual specimen.

Sequencing high molecular weight (HMW) DNA with long-read and linked-read technologies has promoted a major increase in more complete genome sequences for nonmodel organisms. Sequencing approaches that rely on HMW DNA have been limited to larger organisms or pools of multiple individuals, but recent advances have allowed for sequencing from individuals of small-bodied organisms. Here, we use HMW DNA sequencing with PacBio long reads and TELL-Seq linked reads to assemble and annotate the genome from a single individual feather louse (Brueelia nebulosa) from a European Starling (Sturnus vulgaris). We assembled a genome with a relatively high scaffold N50 (637 kb) and with BUSCO scores (96.1%) comparable to louse genomes assembled from pooled individuals. We annotated a number of genes (10,938) similar to the human louse (Pediculus humanus) genome. Additionally, calling phased variants revealed that the Brueelia genome is more heterozygous (∼1%) then expected for a highly obligate and dispersal-limited parasite. We also assembled and annotated the mitochondrial genome and primary endosymbiont (Sodalis) genome from the individual louse, which showed evidence for heteroplasmy in the mitogenome and a reduced genome size in the endosymbiont compared to its free-living relative. Our study is a valuable demonstration of the capability to obtain high-quality genomes from individual small, nonmodel organisms. Applying this approach to other organisms could greatly increase our understanding of the diversity and evolution of individual genomes.

Types and clinical presentation of damaging behaviour - feather pecking and cannibalism in birds

Behavioural disorders, including feather pecking and cannibalism, are a common problem in both domestic and wild birds. The consequences of this behaviour on welfare of birds incur serious economic losses. Pecking behaviour in birds is either normal or injurious. The type of normal pecking behaviour includes non-aggressive feather pecking – allopreening and autopreening. Aggressive feather pecking aimed at maintenance and establishment of hierarchy in the flock is not associated to feathering damage. Injurious pecking causes damage of individual feathers and of feathering as a whole. Two clinical presentations of feather pecking are known in birds. The gentle feather pecking causes minimum damage; it is further divided into normal and stereotyped with bouts; it could however evolve into severe feather pecking manifested with severe pecking, pulling and removal, even consumption of feathers of the victim, which experiences pain. Severe feather pecking results in bleeding from feather follicle, deterioration of plumage and appearance of denuded areas on victim’s body. Prolonged feather pecking leads to tissue damage and consequently, cannibalism. The nume­rous clinical presentations of the latter include pecking of the back, abdomen, neck and wings. Vent pecking and abdominal pecking incur important losses especially during egg-laying. In young birds, pulling and pecking of toes of legs is encountered. All forms of cannibalistic pecking increase morta­lity rates in birds. Transition of various pecking types from one into another could be seen, while the difference between gentle, severe feather pecking and cannibalism is not always distinct.

Cis-acting mutation affecting GJA5 transcription is underlying the Melanotic within-feather pigmentation pattern in chickens

Significance The molecular mechanisms underlying pigmentation patterns in animals is to a large extent an unresolved mystery in biology. For example, compared with mammals, birds show a stunning diversity in pigmentation patterns. This study advances the knowledge concerning the mechanisms creating periodic pigmentation patterns in individual feathers. We show that a mutation upstream of GJA5 encoding a gap-junction protein is causing the Melanotic phenotype in domestic chickens. Melanotic affects within-feather pigmentation patterns by enhancing the contrast between dark- and light-colored regions in the feather. The result implies that cell–cell communications between melanocytes and other cells in the feather follicle play a critical role for pattern formation.

Classification of plumage images for identifying bird species

This paper studies the possibility of using neural networks to classify plumage images in order to identify bird species. Taxonomic identification of bird plumage is widely used in aviation ornithology to analyze collisions with aircraft and develop methods for their prevention. This article provides a method for bird species identification based on a dataset made up in the previous research. A method for identifying birds from real-world images based on YoloV4 neural networks and DenseNet models is proposed. We present results of the feather classification task. We selected several deep learning architectures (DenseNet based) for a comparison of categorical crossentropy values on the provided dataset. The experimental evaluation has shown that the proposed method allows determining the bird species from a photo of an individual feather with an accuracy of up to 81.03 % for accurate classification, and with an accuracy of 97.09 % for the first five predictions.

IGF-1 hormone controls feather moult intensity

Moulting is an essential rite of passage for chicks across the globe, disposing of their downy fluff in favour of majestic flight feathers that bear them aloft. But no one knew how these juvenile aviators orchestrate their transformation. As the ubiquitous hormone insulin-like growth factor 1 (IGF-1) is key to growth in many organisms, Ádám Lendvai and colleagues from the University of Debrecen, Hungary, with collaborators from the Institute of Pharmaceutical Sciences, Switzerland, collected juvenile bearded reedlings (Panurus biarmicus) from the Hortobágy-Halastó wetland reserve in Hungary to find out whether a dose of the hormone would help their moult along.Impressively, the youngsters that received an injection of microscopic particles that gradually released IGF-1 into their blood replaced their feathers faster than the birds that had not received the injection. In addition, the injected birds produced more new feathers; their moult was further along. The new feathers were also in better condition and had fewer blemishes than those of the untreated birds. However, when the team compared how fast the young adults’ individual feathers grew, the hormone hadn't increased their growth rate; the feathers of the untreated birds were growing just as fast.‘These results suggest that an increase in IGF-1 does not speed up feather growth, but may alter moult intensity by initiating the renewal of several feathers simultaneously’, says Lendvai. However, the team suspects that IGF-1 isn't the only hormone involved in restoring birds’ plumage. Explaining that stress can suddenly reduce the amount of IGF-1 in a bird's blood – potentially placing them in peril if the drop occurred at a critical point in the moult – Lendvai suspects that other hormones also play an essential role coordinating the transformation of the bearded reedling youngsters from scruffy balls of fluff to perky adult reed bed residents.

The feather pattern autosomal barring in chicken is strongly associated with segregation at the MC1R locus.

Color patterns within individual feathers are common in birds but little is known about the genetic mechanisms causing such patterns. Here, we investigate the genetic basis for autosomal barring in chicken, a horizontal striping pattern on individual feathers. Using an informative backcross, we demonstrate that the MC1R locus is strongly associated with this phenotype. A deletion at SOX10, underlying the dark brown phenotype on its own, affects the manifestation of the barring pattern. The coding variant L133Q in MC1R is the most likely causal mutation for autosomal barring in this pedigree. Furthermore, a genetic screen across six different breeds showing different patterning phenotypes revealed that the most striking shared characteristics among these breeds were that they all carried the MC1R alleles Birchen or brown. Our data suggest that the presence of activating MC1R mutations enhancing pigment synthesis is an important mechanism underlying pigmentation patterns on individual feathers in chicken. We propose that MC1R and its antagonist ASIP play a critical role for determining within-feather pigmentation patterns in birds by acting as activator and inhibitor possibly in a Turing reaction-diffusion model.

Filoplume morphology covaries with their companion primary suggesting that they are feather-specific sensors

Abstract Do birds detect and respond to forces acting on feathers through filoplumes, which appear to be unique mechanosensory feathers? If filoplumes function as sensors, their morphology should covary with the morphology of their companion feather to better detect feather movements and position. We explore covariation in filoplumes and primaries across 5 species of birds that vary in body size, molt strategy, and the functional life span of their primaries (Green-winged Teal [Anas crecca], Ring-billed Gull [Larus delawarensis], Turkey Vulture [Cathartes aura], Red-tailed Hawk [Buteo jamaicensis], and Red-winged Blackbird [Agelaius phoeniceus]). Filoplumes never extended beyond the coverts and inserted immediately adjacent to the base of their companion primaries, positioning them to detect subtle changes in feather vibration or movement. Far more variation in filoplume number and morphology was due to species differences than to individuals or position in the wing. Across species, filoplume length and number increased with calamus length of primaries. In the 2 species with growing primaries, the number and length of filoplumes were only weakly associated with molting primaries, suggesting that filoplumes were not replaced when their companion primary was replaced. Further, filoplumes associated with a growing primary were not replaced synchronously, leaving others to sense primary position and movement. Finally, filoplume number and length were greatest in Red-tailed Hawks, a species that carries individual feathers for multiple years, but links between filoplume morphology and molt strategy await broader comparative studies. Taken together, the morphology of filoplumes and their replacement schedule relative to their associated primary suggests that they are sensors, capable of detecting subtle differences in the position and movement of their companion feathers.

Quantitative Interspecific Approach to the Stylosphere: Patterns of Bacteria and Fungi Abundance on Passerine Bird Feathers

Feathers are the habitat of a myriad of organisms, from fungi and bacteria to lice and mites. Although most studies focus on specific taxa and their interaction with the bird host, anecdotal data glimpse feathers as holders of a system with its own ecology, what we call here the stylosphere. A major gap in our knowledge of the stylosphere is the ecology of the total abundance of microorganisms, being also rare to find studies that analyze abundance of more than one group of microorganisms at the bird interspecific level. Here, we quantified bacterial and fungi abundances through qPCR on the wing feathers of 144 birds from 24 passerine and one non-passerine bird species from three localities in Southern Spain. Bacteria and fungi abundances spanned three orders of magnitude among individual birds, but were consistent when comparing the right and the left wing feathers of individuals. Sampling locality explained ca. 14% of the variation in both bacteria and fungi abundances. Even when statistically controlling for sampling locality, microbial abundances consistently differed between birds from different species, but these differences were not explained by bird phylogeny. Finally, bird individuals and species having more bacteria also tended to held larger abundances of fungi. Our results suggest a quite complex explanation for stylosphere microorganisms' abundance, being shaped by bird individual and species traits, as well as environmental factors, and likely bacteria-fungi interactions.

Plumage patterns: Ecological functions, evolutionary origins, and advances in quantification

AbstractBirds exhibit remarkable variation in plumage patterns, both within individual feathers and among plumage patches. Differences in the size, shape, and location of pigments and structural colors comprise important visual signals involved in mate choice, social signaling, camouflage, and many other functions. While ornithologists have studied plumage patterns for centuries, recent technological advances in digital image acquisition and processing have transformed pattern quantification methods, enabling comprehensive, detailed datasets of pattern phenotypes that were heretofore inaccessible. In this review, we synthesize recent and classic studies of plumage patterns at different evolutionary and organismal scales and discuss the various roles that plumage patterns play in avian biology. We dissect the role of plumage patches as signals within and among species. We also consider the evolutionary history of plumage patterns, including phylogenetic comparative studies and evolutionary developmental research of the genetic architecture underlying plumage patterns. We also survey an expanding toolbox of new methods that characterize and quantify the size, shape, and distribution of plumage patches. Finally, we provide a worked example to illustrate a potential workflow with dorsal plumage patterns among subspecies of the Horned Lark (Eremophila alpestris) in western North America. Studies of plumage patterning and coloration have played a prominent role in ornithology thus far, and recent methodological and conceptual advances have opened new avenues of research on the ecological functions and evolutionary origins of plumage patterns in birds.

Stable isotopes demonstrate intraspecific variation in habitat use and trophic level of non‐breeding albatrosses

The non‐breeding period is critical for restoration of body condition and self‐maintenance in albatrosses, yet detailed information on diet and distribution during this stage of the annual cycle is lacking for many species. Here, we use stable isotope values of body feathers (δ13C, δ15N) to infer habitat use and trophic level of non‐breeding adult Grey‐headed Albatrosses Thalassarche chrysostoma (n = 194) from South Georgia. Specifically, we: (1) investigate intrinsic drivers (sex, age, previous breeding outcome) of variation in habitat use and trophic level; (2) quantify variation among feathers of the same birds; and (3) examine potential carry‐over effects of habitat use and trophic level during the non‐breeding period on subsequent breeding outcome. In agreement with previous tracking studies, δ13C values of individual feathers indicate that non‐breeding Grey‐headed Albatrosses from South Georgia foraged across a range of oceanic habitats, but mostly in subantarctic waters, between the Antarctic Polar Front and Subtropical Front. Sex differences were subtle but statistically significant, and overlap in the core isotopic niche areas was high (62%); however, males exhibited slightly lower δ13C and higher δ15N values than females, indicating that males forage at higher latitudes and at a higher trophic level. Neither age nor previous breeding outcome influenced stable isotope values, and we found no evidence of carry‐over effects of non‐breeding habitat use or trophic level on subsequent breeding outcome. Repeatability among feathers of the same individual was moderate in δ13C and low in δ15N. This cross‐sectional study demonstrates high variability in the foraging and migration strategies of this albatross population.

How a Bird Gets Its Feathers: Insights from Chromatin Looping.

Mechanisms controlling skin heterogeneity are poorly understood. In this issue of Developmental Cell, Liang etal. show that in chicken, the difference in β-keratin genes expressed in feathered and scaly skin is regulated via typical enhancers, while differential expression within individual feathers correlates with chromatin looping within the gene cluster.

Wing shapes take flight

Biomechanics Birds can dynamically alter the shape of their wings during flight, although how this is accomplished is poorly understood. Matloff et al. found that two mechanisms control the movement of the individual feathers. Whenever the skeleton moves, the feathers are redistributed passively through compliance of the elastic connective tissue at the feather base. To prevent the feathers from spreading too far apart, hook-shaped microstructures on adjacent feathers form a directional fastener that locks adjacent feathers. These features are found across a range of bird sizes; however, because the detachment of the hooks is noisy, they are notably absent in silent fliers, such as barn owls. Science , this issue p. [293][1] [1]: /lookup/doi/10.1126/science.aaz3358

Birds of the Land

Evanthe held still, her limbs pulled into awkward angles—one elbow cocked out to the side, the other braced against a root serving as tripod, both hands gripping the biocular's rubber housing hard enough she was afraid she wouldn't be able to unbend them again. She didn't dare readjust. Didn't dare move her left knee off whatever sharp thing she'd planted it on. She'd been waiting her whole life to see this: a male paradise tanager, gaudy in his array of colors, singing brightly for his mate, the individual feathers of his indigo throat standing out, [….]

Featherwork in Early and Medieval China


 
 
 This paper is concerned with the early documented history of featherwork in China, as described in historical texts and literature up until the end of the Tang dynasty in 907 CE. Although featherwork from several Pacific islands and Latin America has recently been the subject of academic attention, the important Chinese tradition has been neglected. Drawing on studies of featherwork from other cultures, this paper divides these accounts by technical criterion into flexible base featherwork (clothing, curtains, hangings, and coverlets); rigid base featherwork (boxes, architectural detailing, jewelry, and screens); and most remarkably of all, deconstructionist featherwork, whereby the barbs of individual feathers were peeled apart and then spun with a silk core to create a feather thread, which was then woven into cloth. Featherwork was produced in vast quantities in early and medieval China to satisfy demand for these luxurious and brightly colored items, and exotic birds—kingfishers, parrots, pheasants, and so on—were traded across the empire to create these wonderful works of art.
 
 

How localized force spreads on elastic contour feathers.

Birds can experience localized forces against their bodies due to impact against solid objects (like a branch or another bird) or water (during plunge-dives or landings). In this study, we hypothesize that densely packed contour feathers around the bird body would spread localized impact force while diving and maintaining plumage integrity. To test the hypothesis, we performed experiments with individual feathers and elastic beams, and developed a theoretical model to determine the response of feathers during the dive. First, we used a micro computed tomography scanner to characterize the internal structure of the contour feather from a northern gannet and calculate Young's modulus of feathers sampled from different parts of the body. This value was found to be of the order of 109 Pa for feathers from chest and belly. Second, we model the feathers as elastic beams taking into account their pre-curvature and non-uniform cross-section. Results from our experiments with polycarbonate beams suggest that the interaction of feathers on the skin patch redistributes the force, thereby reducing the impact on any particular area of the skin. Finally, a theoretical model of multiple overlaying feathers is proposed to quantify the spreading of impact force on the skin of the bird body which shows that the pressure on the skin at the impact point can be reduced by as much as three times the pressure if feathers had been absent.

Species limits and biogeography of Rhynchospiza sparrows

The genus Rhynchospiza comprises two species, the monotypic Tumbes Sparrow (R. stolzmanni) and the Stripe-crowned Sparrow (R. strigiceps) with subspecies strigiceps and dabbenei. In the study reported here we evaluated the taxonomic status of these taxa and discussed key features involved in speciation. All three taxa exhibited multiple differences in plumage, morphology, and vocalizations, supporting the recognition of three species in Rhynchospiza. The very large-billed R. stolzmanni has a song composed of a succession of faster complex trilled phrases, shows a small black loral line and dark-chestnut head stripes with large dark central-stripe to individual feathers, and is resident in the Tumbes region. The large and heavy dabbenei has a song consisting of a series of simple chirping notes, shows a large black loral crescent and chestnut head stripes with a reduced to absent dark center to feathers, and inhabits the Austral Yungas as a year-round resident. The small and pale strigiceps has a song consisting of a succession of complex trilled phrases, shows a small black loral line and rufous-brown head stripes with large dark central-stripe to feathers, and inhabits Dry and Sierran Chaco where it is a partial migrant. Locality data and ecological niche modeling show that dabbenei and strigiceps are allo-parapatric and use different altitudinally segregated habitats at their zone of parapatry. Molecular phylogenetic analyses (NADH dehydrogenase 2 [ND2] gene) revealed R. stolzmanni to be sister (11.5% divergent) to a recently diverged dabbenei and strigiceps clade (1.6% divergent). We conclude that the genus Rhynchospiza comprises three species-level entities, each restricted to a major biogeographic region, and that vocalizations and facial patterns provide key evidence on species limits in these otherwise similarly plumaged taxa. The evolutionary–cultural differences in songs, with complex phrases in those of R. strigiceps and R. stolzmanni, and single notes in the songs of R. dabbenei, suggest changes in the innate vocal learning template during speciation in the latter.

Aerodynamic interaction of collective plates in side-by-side arrangement

In the tip-reversal upstroke of avian flight, individual feathers twist so as to create gaps between them. Although this behavior allows the feathers to function as individual lift-generating bodies, the lift generation mechanism of these multiple bodies remains unclear. This paper reports a numerical investigation of multiple stationary plates arranged side by side in a uniform flow. The aim is to elucidate the collective mechanism of the flow generated by the plates and the lift contribution of each plate. The angle of attack of each plate and the gap between the plates are varied to determine their influence on the flow and lift of the collection of plates. The time-averaged lift increases from the lowermost to the uppermost plate, and, at a high angle of attack, the total lift coefficient of the plates becomes greater than that of a single plate solely placed in a uniform flow. At a high angle of attack, vortex shedding from the upper plates is synchronized with some phase difference, resulting in synchronized lift fluctuations for individual plates and a reduction in the overall fluctuation amplitude. With an optimal gap ratio and angle of attack, the collective behavior of plates in side-by-side arrangement can be advantageous to enhance lift-generation performance.