The presence and microstructure of down compartments of feathers in representatives of nineteen orders of birds (Aves)

Temporal and energetic constraints associated with migration may compromise plumage quality and, ultimately, flight ability in migratory birds. As a consequence, migrants may invest more resources in parts of the plumage that are essential for long, sustained flight (such as the primary wing feathers) than in less important feather tracts. We used migratory and sedentary Blackcaps (Sylvia atricapilla) to analyze within- and between-individual variation in the mass and quality of wing and tail feathers. Migratory Blackcaps in both adult and juvenile plumage had lighter tail feathers than sedentary Blackcaps, but the primary feathers were of similar mass. Interestingly, the quality of primary and tail feathers (estimated from the mass of the feather in relation to its size) were positively correlated within individuals. However, migratory individuals had higher-quality primary feathers than sedentary individuals, given the quality of their tail feathers. Therefore, migratory Blackcaps appeared to preferentially allocate limited resources to primary feathers at the expense of the quality of the less important tail feathers. We suggest that this represents an adaptive mechanism to reduce the costs of migration constraints on plumage functionality.

Feather mites (Astigmata: Pterolichoidea, Analgoidea) are permanent ectosymbionts of birds, found from all avian orders except Rheiformes (Stefan et al. 2015). The feather mites’ spatial distribution on the plumage depends on the morphology and structure of the feathers, aerodynamic and frictional forces, the life cycle and social behavior of the hosts, as well as environmental factors such as temperature and humidity (Dubinin 1951; Fernández-González et al. 2015). Depending on the location of the feather mites on the host’s body, a variety of morphological, physiological and behavioral adaptations are observed, which allow several feather mite species to coexist on the same bird (Dabert and Mironov 1999; Proctor 2003; Mestre et al. 2011). Studies dedicated to the spatial distribution of feather mites on the plumage of birds are relatively scarce. Such data is largely missing also for the territory of Bulgaria. Therefore, the aim of this paper is to present the results of the first specialized study of their spatial distribution on the plumage of passerines in Bulgaria. 379 birds belonging to 47 species of the order Passeriformes were examined in the period 2005–2007. As a result, the locations of 76,000 specimens (including both adults and nymphal stages) of feather mites of 54 species were determined. The distribution on the plumage of each species of bird was presented by generalized schemes. Feather mites were not found on the outermost primary feathers (P10), which are smaller than others primaries and do not offer enough resources. Feather mites located on the wing and tail feathers were mainly observed on the medial part of the feather, close to the rachis, and hence on the feather barbs. Feather mites preferred the wider parts of the primary feathers. On the secondary feathers, the mites were located predominantly in the middle third, on either side of the rachis. We examined if feather mites were symmetrically distributed on both wings using samples from those birds represented by numerous individuals (Passer montanus (L., 1758), Acrocephalus arundinaceus (L., 1758), Panurus biarmicus (L., 1758), Cyanistes caeruleus (L., 1758), Fringilla coelebs L., 1758). In this analysis, χ2-test confirmed no difference in the location of the feather mites on the feathers of both wings of the respective hosts and symmetry. Mites, such as Proctophyllodes pinnatus (Nitzsch, 1818) and Mesalgoides megnini (Oedemans, 1937) (on Chloris chloris (L., 1758)), Proctophyllodes stylifer (Buchholz, 1869) and Ptronyssoides parinus (Koch, 1841) (on Cyanistes caeruleus), Pterodectes rutilus Robin, 1868 and Scutulanyssus hirundicola Mironov, 1985 (on Hirundo rustica L., 1758), can coexist on the feathers of their respective hosts. Probably the different body size or trophology of these mite species reduced the competition between them. We found Trouessartia crucifera Gaud, 1957 and T. appendiculata (Berlese, 1886) on the secondary feathers of Hirundo rustica, but never together. The competition for resources between these two mite species is probably stronger. Feather mites respond to bird molting mainly by moving to adjacent feathers (Dubinin 1951). We monitored the spatial distribution of Proctohyllodes balati on the wing feathers during the molting of Panurus biarmicus.

Earlier research on feather morphology emphasized comprehensively on the body contour feather than various other types of feathers. Therefore, we conducted a systematic study on all feather types of the Indian Pitta Pitta brachyura, a passerine bird native to the Indian subcontinent. Feather barbs from wing contour, tail contour, body contour, semiplume, down, powder down, and bristle feathers were retrieved from the bird and observed under a light microscope. Primary flight feathers from the right and left wing were longest (85.17 mm and 87.32 mm, respectively), whereas bristle feathers were the shortest (5.31 mm). The mean barb length was observed to be the highest (11.37±0.47 mm) in the wing feather followed by body contour (8.31±0.39 mm), semiplume (8.27±0.22 mm), tail feather (7.85±0.50 mm), down (6.45±0.21 mm), powder down (6.04±0.23 mm), and bristle (2.70±0.07 mm). Pearson correlation was found positive for barb length and feather length of down feathers (r= 0.996, p ≤0.05). We observed a novel type of barb the first time from dorsal body contour feather having plumulaceous barbules at the base followed by pennaceous barbules. This unique barbule arrangement is termed ‘sub-plumulaceous’ as it is distinct and analogous to known ‘sub-pennaceous’ type arrangement found absent in passerines.

Earlier research on feather morphology emphasized comprehensively on the body contour feather than various other types of feathers. Therefore, we conducted a systematic study on all feather types of the Indian Pitta Pitta brachyura, a passerine bird native to the Indian subcontinent. Feather barbs from wing contour, tail contour, body contour, semiplume, down, powder down, and bristle feathers were retrieved from the bird and observed under a light microscope. Primary flight feathers from the right and left wing were longest (85.17 mm and 87.32 mm, respectively), whereas bristle feathers were the shortest (5.31 mm). The mean barb length was observed to be the highest (11.37±0.47 mm) in the wing feather followed by body contour (8.31±0.39 mm), semiplume (8.27±0.22 mm), tail feather (7.85±0.50 mm), down (6.45±0.21 mm), powder down (6.04±0.23 mm), and bristle (2.70±0.07 mm). Pearson correlation was found positive for barb length and feather length of down feathers (r= 0.996, p ≤0.05). We observed a novel type of barb the first time from dorsal body contour feather having plumulaceous barbules at the base followed by pennaceous barbules. This unique barbule arrangement is termed ‘sub-plumulaceous’ as it is distinct and analogous to known ‘sub-pennaceous’ type arrangement found absent in passerines.

Studies of the evolution of elaborate ornaments have concentrated on their role in increasing attractiveness to mates. The classic examples of such sexually selected structures are the elongated tails of some bird species. Elongated tails can be divided into three categories: graduated tails, pin tails and streamers. There seems to be little debate about whether graduated and pin tails are ornaments; i.e. costly signals used in mate choice. However, in the case of streamers there is considerable discussion about their function. It has been suggested that tail streamers could be (i) entirely naturally selected, (ii) entirely sexually selected, (iii) partly naturally and partly sexually selected. The prime example of a species with tail streamers is the swallow (Hirundo rustica) in which both sexes have tail streamers. In this paper we discuss the aerodynamic consequences of different types of manipulation of the streamer and/or outer tail feather. We make qualitative predictions about the aerodynamic performance of swallows with manipulated tail streamers; these predictions differ depending on whether streamers have a naturally or sexually selected function. We demonstrate that these hypotheses can only be separated if tail streamers are shortened and changes in aerodynamic performance measured during turning flight.

Here we investigate the change in feather quality during partial post‐juvenile and complete post‐breeding moult in great tit Parus major by measuring the change in the number of fault bars and feather holes on wing and tail feathers. Feathers grown during ontogeny usually are of lower quality than feathers grown following subsequent moults at independence. This is reflected by higher number of fault bars and feather holes on juveniles compared to adults. Fault bars are significantly more common on tail and proximal wing feathers than on the distal remiges, indicating a mechanism of adaptive allocation of stress induced abnormalities during ontogeny into the aerodynamically less important flight feathers. On the contrary, feather holes produced probably by chewing lice have a more uniform distribution on wing and tail feathers, which may reflect the inability of birds to control their distribution, or the weak natural selection imposed by them. The adaptive value of the differential allocation of fault bar between groups of feathers seems to be supported by the significantly higher recapture probability of those juvenile great tits which have fewer fault bars at fledging on the aerodynamically most important primaries, but not on other groups of flight feathers. The selection imposed by feather holes seems to be smaller, since except for the positive association between hatching date, brood size and the number of feather holes at fledging, great tits' survival was not affected by the number of feather holes. During post‐juvenile moult, the intensity of fault bars drops significantly through the replacement of tail feathers and tertials, resulting in disproportional reduction of the total number of fault bars on flight feathers related to the number of feathers replaced. The reduction in the number of fault bars during post‐juvenile moult associated with their adaptive allocation to proximal wing feathers and rectrices may explain the evolution of partial post‐juvenile moult in the great tit, since the quality of flight feathers can be increased significantly at a relatively small cost. Our results may explain the widespread phenomenon of partial post‐juvenile moult of flight feathers among Palearctic passerines. During the next complete post‐breeding moult, the total number of fault bars on flight feathers has remained unchanged, indicating the effectiveness of partial post‐juvenile moult in reducing the number of adaptively allocated fault bars. The number of feather holes has also decreased on groups of feathers replaced during partial post‐juvenile moult, but the reduction is proportional with the number of feathers moulted. In line with this observation, the number of feather holes is further reduced during post‐breeding moult on primaries and secondaries, resulting in an increase in feather quality of adult great tits.

Oropharyngeal and cloacal swabs have been widely used for the detection of H5N1 highly pathogenic avian Influenza A virus (HPAI virus) in birds. Previous studies have shown that the feather calamus is a site of H5N1 virus replication and therefore has potential for diagnosis of avian influenza. However, studies characterizing the value of feathers for this purpose are not available, to our knowledge; herein we present a study investigating feathers for detection of H5N1 virus. Ducks and chickens were experimentally infected with H5N1 HPAI virus belonging to 1 of 3 clades (Indonesian clades 2.1.1 and 2.1.3, Vietnamese clade 1). Different types of feathers and oropharyngeal and cloacal swab samples were compared by virus isolation. In chickens, virus was detected from all sample types: oral and cloacal swabs, and immature pectorosternal, flight, and tail feathers. During clinical disease, the viral titers were higher in feathers than swabs. In ducks, the proportion of virus-positive samples was variable depending on viral strain and time from challenge; cloacal swabs and mature pectorosternal feathers were clearly inferior to oral swabs and immature pectorosternal, tail, and flight feathers. In ducks infected with Indonesian strains, in which most birds did not develop clinical signs, all sampling methods gave intermittent positive results; 3-23% of immature pectorosternal feathers were positive during the acute infection period; oropharyngeal swabs had slightly higher positivity during early infection, while feathers performed better during late infection. Our results indicate that immature feathers are an alternative sample for the diagnosis of HPAI in chickens and ducks.

Mites on birds: Comment from Harper & Randall

Flight feathers represent a hallmark innovation of avian evolution. Recent comparative genomic analyses identified a 284 bp avian-specific highly conserved element (ASHCE) located within the eighth intron of the SIM bHLH transcription factor 1 (Sim1) gene, postulated to act as a cis-regulatory element governing flight feather morphogenesis. To investigate its functional significance, genome-edited (GE) primordial germ cell (PGC) lines carrying targeted ASHCE deletions were generated using CRISPR/Cas9-mediated editing, with germline chimeric males subsequently mated with wild-type (WT) hens to obtain GE progeny. The resulting GE chickens harbored 257–260 bp deletions, excising approximately half of the Sim1-ASHCE sequence. Reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR) analysis showed an average 0.32-fold reduction in Sim1 expression in the forelimbs of GE embryos at day 8 (E8) compared to WT counterparts. Despite this, GE chickens developed structurally normal flight and tail feathers. In situ hybridization localized Sim1 expression to the posterior mesenchyme surrounding flight feather buds in E8 WT embryos, but not within the buds themselves. These results suggest that partial deletion of Sim1-ASHCE, despite diminishing Sim1 expression, does not disrupt flight feather formation. The excised region appears to possess enhancer activity toward Sim1 but is dispensable for flight feather development. Complete ablation of the ASHCE will be necessary to fully resolve the regulatory role of Sim1 in avian feather morphogenesis.

Latitudinal gradients in environmental conditions shape avian life-history strategies by influencing resource allocation among growth, survival, and reproduction. Feather production, which is essential for flight, thermoregulation, and predator avoidance, represents a key component of avian energy allocation. We examined interspecific variation in wing and tail feather growth rates and quality in passerine birds from European temperate and Afrotropical regions using data from 679 adults representing 132 species from 36 families. Our findings reveal distinct latitudinal differences in feather growth: tropical breeding passerines exhibit significantly faster wing feather growth rates than temperate zone breeding species, while tail feather growth is lower in tropical species. Additionally, fault bars were common in the tail feathers of tropical species but almost absent in wing feathers across both regions. This absence was particularly apparent among temperate breeding long-distance migratory species. Overall, feather traits were strongly influenced by breeding rather than moulting latitudes, suggesting that latitude-driven selection on energy allocation and intrinsic physiological mechanisms shape feather investment strategies. Our results thus indicate that investments in feather traits are part of a recently uncovered and widening spectrum of avian evolutionary syndromes convergently evolving among phylogenetically unrelated lineages sharing the same breeding latitudes.

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

Sexual selection and aerodynamic forces affecting structural properties of the flight feathers of birds are poorly understood. Here, we compared the structural features of the innermost primary wing feather (P1) and the sexually dimorphic outermost (Ta6) and monomorphic second outermost (Ta5) tail feathers of barn swallows (Hirundo rustica) from a Romanian population to investigate how sexual selection and resistance to aerodynamic forces affect structural differences among these feathers. Furthermore, we compared structural properties of Ta6 of barn swallows from six European populations. Finally, we determined the relationship between feather growth bars width (GBW) and the structural properties of tail feathers. The structure of P1 indicates strong resistance against aerodynamic forces, while the narrow rachis, low vane density and low bending stiffness of tail feathers suggest reduced resistance against airflow. The highly elongated Ta6 is characterized by structural modifications such as large rachis width and increased barbule density in relation to the less elongated Ta5, which can be explained by increased length and/or high aerodynamic forces acting at the leading tail edge. However, these changes in Ta6 structure do not allow for full compensation of elongation, as reflected by the reduced bending stiffness of Ta6. Ta6 elongation in males resulted in feathers with reduced resistance, as shown by the low barb density and reduced bending stiffness compared to females. The inconsistency in sexual dimorphism and in change in quality traits of Ta6 among six European populations shows that multiple factors may contribute to shaping population differences. In general, the difference in quality traits between tail feathers cannot be explained by the GBW of feathers. Our results show that the material and structural properties of wing and tail feathers of barn swallows change as a result of aerodynamic forces and sexual selection, although the result of these changes can be contrasting.

Ongoing studies in the region of Zurich, Switzerland, on the Dipper date back to 1987. The Dipper population (about 25 breeding pairs) is located on two streams flowing into Lake Zurich. All the birds are individually marked. Over the years moult records on 247 individuals trapped once or repeatedly per season were collected, however, due to re-trapping of individuals total number of records amounted to 358. Exact age of 238 individuals was known. Moult process was outlined on the basis of all primaries and the outer six secondaries as well as in tail feathers (rectrices). All birds recorded belong to the local population, thus data on individuals and their breeding specifics had been collected over the years and could thus be analysed as to their influence on the moult process. Among passerines flight feather moult in Dippers is exceptional. Feather replacement occurs in accelerated and sporadic waves. This particular trait however does not shorten the overall time required for a moult: the waves occur in sequences and between these periods moult is slowed down. Moult in the secondaries, which, in general, is not initiated until the primaries have obtained their second wave, follows the same pattern. For the Dipper, moult starts on 23 June and ends on 15 September on average; 95% of all initiations lie between 1 June and 15 July. Moult lasts 80 to 88 days (84 days on average) and is thus within the range known for other similar songbird species. No support was found of the hypothesis that given its aquatic lifestyle at least two thirds of the wing feathers have to be intact. Observations on behaviour show that during moult the Dipper forages on the bankside or in shallow water. Analyses of stomach content have confirmed this behaviour. During the stage in which a massive loss of feathers occurs real diving is very rare and the Dipper becomes quite sedentary and even cryptic with otherwise little activity evident. Its wave-like moult seems to be a compromise between a short moulting period within which flight and diving capability is limited. On the whole, male Dippers start to moult 5.2 days earlier than females. A comparison of age classes shows that 89 of secondyear birds initiate moult 5.6 days prior to the 149 older-than-second-year birds. The earlier moult in second-year birds can be explained by the fact that they have retained their plumage for a longer time (hatching date to average moult date in their second year versus average moult date to average moult date in older-than-second-year birds). Among the older-than-secondyear birds the median starting date remains stable. A striking difference becomes evident when comparing 176 early breeders (brood or young reaching independence prior to 22 June) with 71 late breeders (breeding activites after 22 June): the advance group begins moulting 12.5 days earlier than those birds with prolonged breeding acitvities. Within the delayed group males moult 6.1 days earlier than females. In conclusion, moult is dependent on sex, breeding date and breeding activity as well as age.

Abstract. Setianto J, Sutriyono, Prakoso H, Zain B, Adwiyansyah R, Amrullah AHK. 2019. Short Communication: Phenotypic diversity of male Burgo chicken from Bengkulu, Indonesia. Biodiversitas 20: 532-536. Burgo chicken is the result of a crossbreed of Red Junglefowl (Gallus gallus gallus) with Kampung chicken (Gallus domestica). This study aimed to describe the diversity of colors found in male Burgo chickens. The study was conducted in the city of Bengkulu, Indonesia. The method used in this study was a direct observation of the 50 male chickens on the breeders. The breeders belonging to the Burgo chicken community were determined by random sampling method. The breeders who did not join the community were determined by the snowball sampling method. This method was carried out because the presence of breeders who keep Burgo chickens was unknown. The data in this study consisted of the color of chest feathers, neck feathers, wing feathers, tail feathers, saddle feathers, and the number of wing and tail feathers. The data obtained were analyzed descriptively. The number of colors ranges 4 to 11 with the high diversity is mainly found on the feathers of the chest, neck and, saddle.

Legacy and current-use brominated flame retardants in the Barn Owl