Feather Size Research Articles

Maintaining the avian wing aerofoil: Relationships between the number of primary and secondary flight feathers and under‐lying skeletal size in birds

AbstractBird wings vary in size and morphology in terms of both size and number of feathers and the underlying skeletal anatomy. The number of primary remiges does not seem to vary much between bird species but, by contrast, the number of secondary remiges is reported to range between 6 and 40 depending on bird size. Given that the primaries are attached to the manus, and the secondaries are attached to the ulna, it was predicted that as bone lengths increased with increasing size of the bird, then feather count would increase. Data were collected for 268 species from 25 different orders, and phylogenetically controlled analysis explored the allometry between feather count and bone size. The number of primaries was typically 10 or 11 and did not vary with manus size. By contrast, the number of secondaries increased with ulna length, but only in some orders. For example, in Gruiformes, the number of secondary feathers increased concomitantly with ulna length but despite a two orders of magnitude range in body mass, almost all species in the Passeriformes had nine secondary remiges. It is unclear why, for instance, species with an ulna length of 70 mm can have between 9 and 24 secondaries depending on their order. This variation in secondary feather number can be added to variation in relative wing bone lengths, flight feather lengths, flight feather mechanical properties, and flight feather vane densities as another potential mechanism of adaptation to flight requirements. The apparent constraint of wingspan is scaling as approximately body mass1/3. Further research is needed to explore whether changes in secondary feather number relative to ulna length are accompanied by changes in feather vane width or the overlap of adjacent feathers and how this relates to wing aerodynamics.

Marginal-covert moult in the House Sparrow Passer domesticus

ABSTRACT Marginal coverts are often neglected in passerine moult studies due to their small size and large number. Here, we document eight moult components of this group of wing coverts in a House Sparrow population from Barcelona in 2018–21: timing, growth rate, intensity, speed, duration, sequence, extent and barb density. We also tested the influence of various intrinsic and extrinsic factors on marginal-covert moult. Our adult population started marginal-covert moult on 29 July and finished it on 29 August, with the moult of hatch-year birds delayed 13 days in relation to the moult of adults. Growth rate of the largest marginal covert increased significantly with its size but did not differ between sexes. Intensity of marginal-covert moult replacement was not constant during the moult progress, which took 32 days on average. Moult sequence of marginal coverts started with the proximal feathers, proceeded distally replacing the central rows and was completed toward the front and rear rows. Moult extent was complete except in one case. Size of the largest marginal covert increased with calamus width, but not significantly, and barb density decreased with feather size, but not significantly, and neither measure differed between sexes. Comparison with published results indicated that growth rate is lower in marginal coverts than in primaries and rectrices, whereas barb density is greater. Linear regression of marginal-covert size on both growth rate and barb density can be used to predict growth rate and barb density of flight feathers in the House Sparrow.

Topology optimization of thermal–fluid problem using the MMC-based approach

The moving morphable components (MMC)-based approach has advantages in describing geometry explicitly, feature size controlling, etc., and it has been successfully used for the topology design of bearing structures. In this work, the MMC-based approach is extended to thermal-fluid design which is formulated as a heat transfer maximization and fluid power dissipation minimization problem controlled by Navier–Stokes (N–S) and energy balance equations. Aiming at describing the geometry of bend pipes which usually have a larger curvature than the bearing structures, a cubic order component with elliptic joints is proposed. In order to limit the minimum width of pipes according to the manufacturing capacity, a feature size control technique is developed. The algorithm is investigated on a two-dimensional numerical model by comparing with density-based method and MMC approach with quadratic components. In our tests, besides the advantage of feather size controlling, the developed MMC also achieves lower objective values than the other two methods.

The allometry of number of feathers in birds changes seasonally

Feathers are a defining feature of birds with multiple functions such as flight, insulation, protection against predation and signaling. Feathers are lost during the annual molt while the rate of such loss at other times of the year and its fitness consequences remain poorly known. I used information on the number and the mass of feathers for 160 individuals belonging to 85 species of birds in general linear mixed models to analyze allometry of feathers and to investigate possible factors explaining variation in the number of feathers. A phylogenetic effect was assessed by quantifying the random effect of genus. The total mass of feathers increased isometrically with body mass, while the total number of feathers and the mean mass of feathers showed negative allometry. Negative allometry implied that small-sized species had relatively many small feathers. There was a negative association between the number of feathers and migration distance. The total number of feathers initially increased during fall and winter, consistent with individuals growing more feathers later during the year or with individuals with fewer feathers selectively disappearing from the population. In contrast, the number of feathers decreased from winter through spring and summer. These findings suggest that thermoregulation has affected the evolution of the number and the size of feathers, there is selection against feather loss, and that the number of feathers varies across seasons.

Experimental study of dew formation on metal radiant panels

The risk of condensation on radiant cooling panels used in hot and humid regions has limited their application and broad adoption in the market. This paper describes an experimental study of dew formation on metal radiant panels. Two metal radiant panels with hydrophobic and untreated aluminum alloy surfaces were prepared for investigation and a constant temperature and humidity environmental chamber was employed to simulate the various indoor thermal environments. The results indicate that sub-cooled degrees had a significant effect on the elapsed time from the condensate nucleating to falling off the horizontal radiant panels, which was over 10h at a sub-cooled degree less than 3°C. In addition, the hydrophobic surface demonstrated a delaying effect on the dew formation on the radiant panels. The feature size of the critical pendant droplet falling off the hydrophobic surface (with a contact angle of 96.7°) was 5.6mm, while that of the untreated aluminum alloy surface (with a contact angle of 66.1°) was 7.3mm. Furthermore, simulation results show that the feather size of the critical pendant droplet falling off the horizontal surface decreases as the contact angle increases. Based on these results, hydrophobic surfaces represent a promising new method for limiting condensation on radiant panels.

Phenotypic variation of Forest Thrushes Turdus lherminieri in Guadeloupe: evidence for geographic differentiation at fine spatial scale

Spatial differentiation in avian models has been extensively studied at a coarse scale for both theoretical and conservation purposes. Yet, studies at a finer spatial scale are also particularly relevant in birds because their dispersal ability may be much more reduced than expected. In the Forest Thrush Turdus lherminieri, we studied morphological characters commonly used to assess differentiation because they mirror both demographic and selective processes. The Forest Thrush is an endemic and vulnerable Antillean bird species which has dramatically declined in the last 15 years, and whose population functioning and structure remain unknown. We compared birds from 11 sites in Guadeloupe, which were distributed from 2 to 42 km apart over the two main geographic zones of the island (i.e. Grande-Terre and Basse-Terre). Using two synthetic descriptors (for body size and feather size), we detected a strong micro-geographic differentiation between Forest thrush populations for the body-size descriptor but not for the feather-size descriptor. Both males and females were significantly larger in Basse-Terre than in Grande-Terre despite the fine geographic scale. Several hypotheses could explain these results: (i) geographic isolation and differentiation caused by (1)absence of gene flow, (2) phenotypic plasticity, or (3) divergence with gene flow. Although further investigation is needed to identify the exact process generating phenotypic divergence, our study provides a first highlight to the high local variability of this species.

Is Carrying Feathers a Sexually Selected Trait in House Sparrows?

AbstractMales in several avian groups carry specialised materials as part of their courtship display. Females may vary their investment in reproduction in relation to their mates' attractiveness. The house sparrow (Passer domesticus) population on Dassen Island, South Africa, builds domed nests in the branches of trees. These nests are more or less spherical structures with a deep cup lined largely with feathers. When males collect feathers, they call to females and display the feather before it is added to the nest. We examined whether carrying feathers provides females with an index of male quality, which correlates with their subsequent investment in parental care. Additionally, we studied the potential importance of feathers in nest insulation. Feathers were collected mainly by males. Males also brought larger feathers, and deposited more feathers in nests, than females. Number of trips with feathers – which increased after feathers were experimentally removed from nests – and number of feathers brought varied among males. Volume of feathers influenced females' investment in reproduction and positively correlated with clutch size and chick feeding rates. We found more feathers during incubation and immediately after chicks hatched, when nest heat requirements peak. Furthermore, number of trips with feathers and number and size of feathers were greater during incubation. Our results suggest that this feather‐carrying behaviour by male house sparrows influences maternal reproduction investment and could be a kind of parental care per se by supplementing nest insulation.

REMOVAL OF CHROMIUM IONS FROM INDUSTRIAL WASTE EFFLUENTS BY ADSOPTION

Abstract Heavy metals are unacceptable pollutants if present in industrial or urban wastes, due to their highly toxic effects for humanity. Chromium ions, especially if in the hexavalent form, are one of these undesirable waste contents. They may be present in industrial solid or liquid effluents, especially those from tanneries and dyeing plants, which will appear finally in the effluent liquids, and perhaps solids. The objective of the present investigation is to remove chromium ions, by the adsorption technique, from liquid and/or solid effluents in order that these may be safely disposed in rivers, canals or draining exits. Chicken feathers, were chosen to be the solid adsorbent. This will decrease land environmental pollution by feathers and will remove chromium ions from liquid wastes, as well. The factors affecting the removal process were examined such as equilibrium time, feather charges, mixing conditions and the pH of the waste solution. The best results were obtained at 1 and 2 values of the pH. Equilibrium modeling has been carried out using Langmuir, Freundlish and Redlish- Peterson models. The correlation between the three isotherms and experimental data was found to be reasonable in all cases. A simple kinetic model has been developed to explain the external mass transport of chromium from water onto chicken feathers and determine the external mass transfer coefficient, Ks under influence of a number of design variables, namely agitation seep, size and mass of chicken feathers. By log-log correlation, it has been proved that Ks varies linearly with agitation, size and mass of chicken feathers.

Goshawk prey have more bacteria than non‐prey

1. Predators often prey on individuals that are sick or otherwise weakened. Although previous studies have shown higher abundance of parasites in prey, whether prey have elevated loads of micro-organisms remains to be determined. 2. We quantified the abundance of bacteria and fungi on feathers of woodpigeons Columba palumbus L., jays Garrulus glandarius L. and blackbirds Turdus merula L. that either fell prey to goshawks Accipiter gentilis L. or were not depredated. 3. We found an almost three-fold increase in bacterial load of prey compared with non-prey, while there was no significant difference between prey and non-prey in level of fungal infection of the plumage. 4. The results were not confounded by differences in size or mass of feathers, date of collection of feathers, or date of analysis of feathers for micro-organisms. 5. These findings suggest a previously unknown contribution of bacteria to risk of predation, with important implications for behaviour, population ecology and community ecology.

Effects of immune activation and glucocorticoid administration on feather growth in greenfinches

Elevation of glucocorticoid (GC) hormone levels is an integral part of stress response (as well as its termination) and immunomodulation. These hormones are also responsible for mobilizing energy stores by stimulation of gluconeogenesis and inhibition of protein synthesis. Elevation of GCs is thus incompatible with other protein-demanding processes, such as moult. Previous studies have shown that chronic elevation of GC hormones suppresses feather growth. Here, we asked whether similar effect would also occur in the case of acute GC elevation and induction of an inflammatory response by foreign antigen. We performed an experiment on captive wild-caught greenfinches (Carduelis chloris) injecting birds with phytohaemagglutinin (PHA) and dexamethasone (DEX) in a factorial design. To assess the possible somatic impacts of these manipulations, we removed one of the outermost tail feathers before the experiment and measured mass and rachis diameter and length of the replacement feathers grown in captivity. Immunostimulation by PHA reduced rachis length, but did not affect feather mass or rachis diameter. Single injection of a synthetic GC hormone DEX significantly reduced all three parameters of feather size. Altogether, these findings demonstrate the sensitivity of feather growth to manipulation of immune and adrenal functions. Our results corroborate the somatic costs of immune activation and suggest that even a short-term elevation of GC hormones may induce long-term somatic costs with a potential impact on fitness. Our findings also imply that a single injection of DEX, frequently used as a diagnostic tool, can have lasting effects and researchers must consider this when designing experiments.

Body feathers as a potential new biomonitoring tool in raptors: A study on organohalogenated contaminants in different feather types and preen oil of West Greenland white-tailed eagles ( Haliaeetus albicilla)

We investigated the variation in concentrations and profiles of various classes of organohalogenated compounds (OHCs) in different feather types, muscle tissue and preen oil from 15 white-tailed eagle ( Haliaeetus albicilla) carcasses from Greenland. The influence of moult patterns and potential external contamination onto the feather surface was examined, while the present study is also the first to investigate the use of body feathers for OHC monitoring. Concentrations of sum polychlorinated biphenyls (PCBs) in feathers from white tailed eagles ranged from 2.3 ng/g in a primary wing feather to 4200 ng/g in body feathers. Using 300 mg of body feathers, almost 50 different OHCs could be quantified and median concentrations in body feathers were 10 fold higher than concentrations in tail feathers (rectrices) or primary wing feathers. Body feathers could be very useful for biomonitoring taking into account their easy sampling, short preparation time and high levels of OHCs. In addition, the effects of confounding variables such as feather size, moult and age are also minimised using body feathers. Correlations with concentrations in muscle tissue and preen oil were high and significant for all feather types ( r ranging from 0.81 to 0.87 for sum PCBs). Significant differences in concentrations and profiles of OHCs were found between different primary feathers, indicating that the accumulation of OHCs in feathers varies over the moulting period (maximum three years). Washing of feathers with an organic solvent (acetone) resulted in a significant decrease in the measured concentrations of OHCs in feathers. However, our results indicated that preen oil is probably not the only contributor to the external contamination that can be removed by washing with acetone. Possibly dust and other particles may be of importance and may be sticking to the preened feathers. Rectrices washed only with water showed high and significant correlations with concentrations in muscle and preen oil as well. Washing with acetone therefore does not seem to be of great influence when relating to internal tissue concentrations. We recommend washing feathers only with distilled water in order to remove dirt and dust particles before analysis.

Validating growth and development of a seabird as an indicator of food availability: captive-reared Caspian Tern chicks fed ad libitum and restricted diets

For seabirds raising young under conditions of limited food availability, reducing chick provisioning and chick growth rates are the primary means available to avoid abandonment of a breeding effort. For mostseabirds,however,baselinedatacharacterizingchickgrowthanddevelopmentunderknownfeedingconditions are unavailable, so it is difficult to evaluate chick nutritional status as it relates to foraging conditions near breeding colonies. To address this need, we examined the growth and development of young Caspian Terns (Hydroprogne caspia), a cosmopolitan, generalist piscivore, reared in captivity and fed ad libitum and restricted (ca. one-third lower caloric intake) diets. Ad libitum-fed chicks grew at similar rates and achieved a similar size at fledging as previously documented for chicks in the wild and had energetic demands that closely matched allometric predictions. We identified three general characteristics of food-restricted Caspian Tern chicks compared to ad libitum chicks: (1) lower age-specific body mass, (2) lower age-specific skeletal and feather size, such as wing chord length, and (3) heightened levels of corticosterone in blood, both for baseline levels and in response to acute stress. Effects of diet restriction on feather growth (10-11% slower growth in diet-restricted chicks) were less pronounced than effects on structural growth (37-52% slower growth) and body mass (24% lower at fledging age), apparently due to preferential allocation of food resources to maintain plumage growth. Our results suggest that measurements of chick body mass and feather development (e.g., wing chord or primary length) or measurement of corticosterone levels in the blood would allow useful evaluation of the nutritional status of chicks reared in the wild and of food availability in the foraging range of adults. Such evaluations could also inform demography studies (e.g., predict future recruitment) and assist in evaluating designated piscivorous waterbird conservation (colony) sites.

Morphological, behavioural and genetic differentiation within the Horned Parakeet (Eunymphicus cornutus) and its affinities to Cyanoramphus and Prosopeia

We revise the taxonomy of the two parakeet taxa in the psittaciform genus Eunymphicus—E. cornutus cornutus (Horned Parakeet) and E. c. uvaeensis (Ouvéa Parakeet)—which are restricted to New Caledonia and the Loyalty Islands, in the south-western Pacific, and we investigate their relationship with the genera Cyanoramphus, considered traditionally as its closest related genus, and Prosopeia. We used three sets of characters to assess the level of differentiation between the Eunymphicus taxa: behaviour (vocalisations), morphology (biometrics and plumage coloration) and genetic (mitochondrial cytochrome b DNA sequence variation, 924 nucleotides). The analysis of vocalisations revealed significant differences, as did morphological analyses (size and number of feathers of the crest, size of the bill, and colour pattern of the head). Genetic distance between the Horned and Ouvéa Parakeets is similar to that recorded between closely related species of Cyanoramphus and both taxa possess novel and diagnostic synapomorphic substitutions. From these genetic, behavioural and morphological data, the two Eunymphicus taxa should be considered separate species, a suggestion that is supported by ecological data as well as anecdotal data on hybridisation from captive birds. Our molecular data also support the traditional view that Cyanoramphus is the closest relative of Eunymphicus, with Prosopeia a sister group to this clade. The consistency with which Platycercus clusters next to the Cyanoramphus—Eunymphicus—Prosopeia grouping suggests that Platycercus may well be the next closest relative of this clade.

Feather development under environmental stress: lead exposure effects on growth patterns in Great Tits Parus major

Capsule Regrowth rate of tail feathers is more strongly affected compared to feather length and symmetry. Aims To assess the value of avian feathers as bioindicators. Methods The origin and persistence of fluctuating asymmetry (FA) in homologous pairs of regrowing feathers was studied in captive birds under different levels of environmental stress, respresented by exposure to lead (Pb). Homologous feathers of individually housed birds were plucked synchronously or with a delay of seven days. We measured growth rate, regeneration time, final size and FA of regrown feathers and related them to Pb stress. Results Asymmetry decreased as feathers reached their final length. This was not due to compensatory growth but rather a consequence of the programmed growth trajectory of single feathers. Tail feathers grown under higher Pb pollution showed increased regeneration times, decreased growth rates and shorter lengths, but no changes in development times nor in FA. For differences between both (i) original and induced feathers and (ii) control and Pb treatment, effect sizes of parameters related to feather development (growth bar width, growth rate, regeneration and development time) were consistently larger than those related to the resulting phenotype (feather length and FA). Conclusions Growth bar widths in particular provide an applicable, sensitive and reliable indicator of adverse conditions such as Pb pollution and experimental conditions. In general, phenotypic characteristics that retrospectively allow estimation of growth rates may be more suitable for monitoring environmental stress than sizes or asymmetries of full-grown traits.

Heat treatment and microbial digestion of poulty feather for biogas production

The aim of this research was the elaboration of the technological parameters of heat pre-treatment and microbial digestion of poultry feathers for biogas production. Feathers were treated at 70, 100, 140 °C, and subsequently digested by Bacillus licheniformis, or keratin disintegrator bacteria. Investigations focused on the optimalization of parameters influencing poultry feather biodegradation. The optimal range of pH, temperature,feather size and bacillus:feather ratio were determined in the experiments, as well as the analysis of relationship between the examined parameters. In order to be able to track the dynamics of the biodegradation, we determined the extinction level of the liquid phase of the biodegraded material in the different experimental treatments. The results showed that the rate of hydrolysis was significantly higher in the treatments with bacteria than in the treatments without it. Regarding the pretreatments at 70, 100 and 140 °C, the digestion of feather was the most intensive at 70 °C. The most extensive digestion was observed in case of 1:3 feather:water ratio. The highest intensity of feather digestion wasdetected in the treatment with 1% microbe ratio.

The examination of poultry feather digestility for biogas production

The aim of this research was the elaboration of the technological parameters of biological digestion and biogas production from poultry feather produced in large quantities by slaughterhouses. Feather protein was digested by Bacillus licheniformis, keratin desintegrator bacteria. Investigations focused on the optimalization of parameters influencing poultry feather biodegradation. The optimal range of pH, temperature, feather size and bacillus:feather ratio were determined in the experiments as well as the analysis of relationship between the examined parameters. In order to be able to track the dinamics of the biodegradation, we determined the extintion level of the liquid phase of the biodegraded material in the different experimental treatments. The results showed that the rate of hydrolisis was significantly higher in the treatments with bacteria than in the treatments without it. The most extensive digestion were observed in case of 1:3 feather:water ratio. The highest intensity of feather digestion were detected in the treatment with 1% microbe ratio.

Cell organization of barb ridges in regenerating feathers of the quail: implications of the elongation of barb ridges for the evolution and diversification of feathers

AbstractThis ultrastructural study on the regenerating feathers of quail describes the cellular organization of the barb ridges responsible for the ramification of adult feathers. Bilateral symmetry of the barb ridges determines the organization of feather cells into feather branching. The length of the barb ridges, derived from the number of cells associated to form the barbule plates, determines the length of the barbule branching. Long chains of barb cells form long barbs that branch from the rachis with an increase of feather size. Supportive cells function as spacers between the barbule cells. New cells derive from stem cells localized in the collar region of the feather follicle, as indicated from the re‐organization of collar cells into barb ridges (a morphogenetic process inherited from that of embryonic feathers), production of an embryonic type of keratin (feather keratin), permanence of periderm granules (typical embryonic organelles) in barb vane ridge cells. Variations in the process of barb ridge morphogenesis allow the fusion of ridges into a rachis. The differentiation of hooklets contributes to the origin of planar feathers. Separation between rachis and merging barb ridges is by supportive cells, derived from the marginal plates of the barb ridges. Speculations on the evolution and diversification of feathers are presented.

Cell structure of barb ridges in down feathers and juvenile wing feathers of the developing chick embryo: Barb ridge modification in relation to feather evolution

The present study deals with the cell structure and three-dimensional organization of barb and barbule cells within barb ridges of down feathers and juvenile feathers in the chick embryo. Juvenile feathers represent the second generation of feathers in the wing, and replace down feathers some weeks after hatching. Within the follicle of juvenile feathers, at 16-18 days of embryonic development, barb ridges are more numerous than in down feathers. Barb ridges of juvenile feathers contain more cells in their barbule and axial plates with respect to barb ridges of down feathers. This condition determines the formation of longer barbules inserted in the rami of juvenile feathers than barbules of down feathers. Barb ridges of juvenile feathers merge with the rachidial ridge so that pennaceous feathers are formed. Barbule cells are surrounded by cytoplasmic elongation from barb vane ridge cells located in the axial plate, which constitute most of the axial plate. The degeneration of supportive cells among barbule cells branching from barbs determine the formation of spaces between barbules. The study emphasizes that, in addition to the size of the dermal papilla, it is the length of barb ridges and the infiltration of barb ridge vane cells among barbule cells that determine the size and length of feathers. The knowledge of the cell structure of barb ridges allows understanding not only of how feathers develop but also gives insights into their evolution. Based on changes of the process of barb ridge morphogenesis some hypotheses on the evolution of plumulaceous and pennaceous feathers are presented. Feathers derived from the process of carving-out supportive cells within barb ridges and from the specific pattern of fusion of barb/barbule cells. This process initially produced variably branched down feathers and later, after barb ridge fusion, a rachis. From the modulation in the pattern of barb ridge formation various pennaceous feathers later evolved.

ECOMORPHOLOGY OF PARASITE ATTACHMENT: EXPERIMENTS WITH FEATHER LICE

The host specificity of some parasites can be reinforced by morphological specialization for attachment to mobile hosts. For example, ectoparasites with adaptations for attaching to hosts of a particular size might not be able to remain attached to larger or smaller hosts. This hypothesis is suggested by the positive correlation documented between the body sizes of many parasites and their hosts. We adopted an ecomorphological approach to test the attachment hypothesis. We tested the ability of host-specific feather lice (Phthiraptera: Ischnocera) to attach to 6 novel species of pigeons and doves that vary in size by nearly 2 orders of magnitude. Surprisingly, Rock Pigeon lice (Columbicola columbae) remained attached equally well to all 6 novel host species. We tested the relative importance of 3 factors that could facilitate louse attachment: whole-body insertion, tarsal claw use, and mandible use. Insertion, per se, was not necessary for attachment. However, insertion on coarse feathers of large hosts allowed lice to access feather barbules with their mandibles. Mandible use was a key component of attachment regardless of feather size. Attachment constraints do not appear to reinforce host specificity in this system.

Developmental mechanisms facilitating the evolution of bills and quills.

Beaks and feathers epitomize inimitable avian traits. Within individuals and across species there exists astounding diversity in the size, shape, arrangement, and colour of beaks and feathers in association with various functional adaptations. What has enabled the concomitantly divergent evolution of beaks and feathers? The common denominator may lie in their developmental programmes. As revealed through recent transplant experiments using quail and duck embryos, the developmental programme for each structure utilizes mesenchyme as a dominant source of species-specific patterning information, acts as a module of closely coupled molecular and histogenic events, and operates with a high degree of spatial and temporal plasticity. By synergizing these three features, the developmental programmes underlying beaks and feathers likely have the essential potential to react spontaneously to novel conditions and new gene functions, and as a consequence are well equipped to generate and accommodate innovative phenotypes during the course of evolution.