Primary Flight Feathers Research Articles

Spontaneous Wing Tip Edema in Captive Birds of Prey: Review of 41 Cases in the United Kingdom (2004-2022).

There is limited literature regarding wing tip edema (WTE) in raptors, and much of our current understanding of the condition is based on anecdotal reports. The aims of this retrospective study were to describe the clinical features of WTE in birds of prey, to identify prognostic factors for return to flight and patient survival following diagnosis, and to develop and assess the clinical significance of a novel WTE grading system. Between 2004 and 2022, 41 cases of WTE were identified in 39 captive birds. No cases were found in wild birds. Harris's hawks (Parabuteo unicinctus), lanner falcons (Falco biarmicus), and peregrine falcons (Falco peregrinus) had the highest frequencies of WTE, and all cases presented between October and May. Increasing days of air frost per month and colder median monthly temperatures were significant risk factors for the development of WTE. Of the cases where patient outcomes were known, 23/31 (74.2%) cases returned to normal flight and 29/34 (85.3%) cases survived. End-stage disease, represented by primary flight feather loss and metacarpal ischemic (dry) gangrene, and enalapril use were associated with poor patient outcomes. Presentation within 24 hours of disease onset, isoxsuprine use, and physiotherapy were associated with improved patient outcomes. This study showed that WTE is an infrequently encountered but clinically significant condition in captive raptors and is associated with an overall high morbidity and moderate mortality risk.

Patterns of integrated growth of body parts in Rook (Corvus frugilegus) ontogeny.

The early period of ontogeny is key to understanding the patterns of body plan formation in birds. Most studies of avian development have focused on the development of individual avian characters, leaving their developmental integration understudied. We explored the dynamics and integration of relative percentage increments in body mass, lengths of head, skeletal elements of wing and leg, and primary flight feathers in the embryonic and postnatal development of the Rook (Corvus frugilegus). The relative percentage increments were calculated according to Brody's equation. Groups of similar growing traits (modules) were determined using hierarchical cluster analysis, and the degree of correlation between modules was estimated by PLS analysis. The embryonic and postnatal periods demonstrate significant consistency both in the dynamics of changes in relative percentage increments of studied traits as well as in the clustering of individual modules. The modules mainly include the body mass and head length, as well as the elements that form the fore- and hind limbs. Differences were revealed in the combination of modules into clusters in embryonic and postnatal periods. Hind limb elements clustered together with wing elements in the embryonic period but with body mass and the head in the postnatal period. The strongest modularity was noted for the leg in embryogenesis, and for the wing in postnatal development. The forelimb and especially the primary feathers had more distinctive growth patterns. We suggest the changes in the degree of integration between locomotor modules in ontogenesis are connected with the earlier functioning of the legs in the postnatal period and with the preparation of the wings for functioning after a chick leaves the nest.

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.

Energy considerations and flow fields over whiffling-inspired wings

Some bird species fly inverted, or whiffle, to lose altitude. Inverted flight twists the primary flight feathers, creating gaps along the wing’s trailing edge and decreasing lift. It is speculated that feather rotation-inspired gaps could be used as control surfaces on uncrewed aerial vehicles (UAVs). When implemented on one semi-span of a UAV wing, the gaps produce roll due to the asymmetric lift distribution. However, the understanding of the fluid mechanics and actuation requirements of this novel gapped wing were rudimentary. Here, we use a commercial computational fluid dynamics solver to model a gapped wing, compare its analytically estimated work requirements to an aileron, and identify the impacts of key aerodynamic mechanisms. An experimental validation shows that the results agree well with previous findings. We also find that the gaps re-energize the boundary layer over the suction side of the trailing edge, delaying stall of the gapped wing. Further, the gaps produce vortices distributed along the wingspan. This vortex behavior creates a beneficial lift distribution that produces comparable roll and less yaw than the aileron. The gap vortices also inform the change in the control surface’s roll effectiveness across angle of attack. Finally, the flow within a gap recirculates and creates negative pressure coefficients on the majority of the gap face. The result is a suction force on the gap face that increases with angle of attack and requires work to hold the gaps open. Overall, the gapped wing requires higher actuation work than the aileron at low rolling moment coefficients. However, above rolling moment coefficients of 0.0182, the gapped wing requires less work and ultimately produces a higher maximum rolling moment coefficient. Despite the variable control effectiveness, the data suggest that the gapped wing could be a useful roll control surface for energy-constrained UAVs at high lift coefficients.

Aerodynamic vs. frictional damping in primary flight feathers of the pigeon Columba livia

During flight, vibrations potentially cause aerodynamic instability and noise. Besides muscle control, the intrinsic damping in bird feathers helps to reduce vibrations. The vanes of the feathers play a key role in flight, and they support feathers’ aerodynamic function through their interlocked barbules. However, the exact mechanisms that determine the damping properties of the vanes remain elusive. Our aim was to understand how the structure of the vanes on a microscopic level influences their damping properties. For this purpose, scanning electron microscopy (SEM) was used to explore the vane’s microstructure. High-speed videography (HSV) was used to record and analyze vibrations of feathers with zipped and unzipped vanes upon step deflections parallel or perpendicular to the vane plane. The results indicate that the zipped vanes have higher damping ratios. The planar surface of the barbs in zipped vanes is responsible for aerodynamic damping, contributing 20%–50% to the whole damping in a feather. To investigate other than aerodynamic damping mechanisms, the structural and material damping, experiments in vacuum were performed. High damping ratios were observed in the zipped vanes, even in vacuum, because of the structural damping. The following structural properties might be responsible for high damping in feathers: (i) the intact planar surface, (ii) the interlocking of barbules, and (iii) the foamy inner material of the barb’s medulla. Structural damping is another factor demonstrating 3.3 times (at vertical deflection) and 2.3 times (at horizontal deflection) difference in damping ratio between zipped and unzipped feathers in vacuum. The shaft and barbs filled with gradient foam are thought to increase the damping in the feather further.

A new biologging approach reveals unique flightless molt strategies of Atlantic puffins.

Animal-borne telemetry devices provide essential insights into the life-history strategies of far-ranging species and allow us to understand how they interact with their environment. Many species in the seabird family Alcidae undergo a synchronous molt of all primary flight feathers during the non-breeding season, making them flightless and more susceptible to environmental stressors, including severe storms and prey shortages. However, the timing and location of molt remain largely unknown, with most information coming from studies on birds killed by storms or shot by hunters for food. Using light-level geolocators with saltwater immersion loggers, we develop a method for determining flightless periods in the context of the annual cycle. Four Atlantic puffins (Fratercula arctica) were equipped with geolocator/immersion loggers on each leg to attempt to overcome issues of leg tucking in plumage while sitting on the water, which confounds the interpretation of logger data. Light-level and saltwater immersion time-series data were combined to correct for this issue. This approach was adapted and applied to 40 puffins equipped with the standard practice deployments of geolocators on one leg only. Flightless periods consistent with molt were identified in the dual-equipped birds, whereas molt identification in single-equipped birds was less effective and definitive and should be treated with caution. Within the dual-equipped sample, we present evidence for two flightless molt periods per non-breeding season in two puffins that undertook more extensive migrations (>2000 km) and were flightless for up to 77 days in a single non-breeding season. A biannual flight feather molt is highly unusual among non-passerine birds and may be unique to birds that undergo catastrophic molt, i.e., become flightless when molting. Although our conclusions are based on a small sample, we have established a freely available methodological framework for future investigation of the molt patterns of this and other seabird species.

Where was WAIR in avian flight evolution?

Abstract The popular hypothesis that the flapping flight of birds evolved through the stage of wing-assisted incline running (WAIR) is tested through calculations of external forces acting on the wings in the downstroke and upstroke during WAIR activity of an adult chukar partridge (Alectoris chukar). Contrary to previous studies of WAIR, it is found that the total vertical impulse provided by the wings is negative (i.e. downward directed). Thus, the wings cancel out about half of the positive (upward-directed) impulse provided by the legs. The function of the wings in WAIR is not to lift the body, but to push it towards the steep slope. It is like a wing, or aerofoil, of a race car, which is tilted at a negative angle of attack to press the car to the ground for greater friction and adhesion of the wheels and to prevent the race car from becoming airborne. The calculated force pattern suggests that the dominant external forces acting on the wings in the sagittal plane during WAIR are not the virtual forces of inertia but the aerodynamic forces. More specifically, it is only the aerodynamic lift that can be responsible for the wing force component acting at right angles to the wingbeat plane in both the downstroke and the upstroke during WAIR. The lift towards the slope during the WAIR upstroke is ensured by separation of the primary flight feathers and their setting at a negative angle of attack. Analysis of the force pattern in the anatomical coordinate space of a bird’s body shows that the main wing muscles in the WAIR downstroke are the humeral retractor muscles and in the WAIR upstroke the humeral elevator muscles. The humeral protractor muscles are not required at all during WAIR. Therefore, the morphologically necessary protractor state of the supracoracoideus muscle in a ‘semi-flying’ ancestor, which is logically explained by the classical hypothesis of a gliding ancestor, does not fit the WAIR hypothesis of flapping flight origin. Wing-assisted incline running should be regarded as a crown locomotor specialization of birds and is not an appropriate model for locomotion in avian ancestors.

Microscopy imaging and modeling study on the mechanical properties of the primary flight feather shaft of the bean goose, Anser fabalis.

Avian flight feathers have the unique advantages of lightweight and high strength, which play a key role in their flight capacity. In this article, the rachis of the bean goose's primary flight feather was used as the research object. Its compressive properties were analyzed and the 3D microscale was observed by 3D microscope system with a super wide depth of field. The distribution of mechanical properties, section variation of fiber and internal microstructure of rachis were obtained by micro-CT technique. Based on these results, a 3D reconstructed model was established for structure mechanical simulation. The simulation results were close basically to the compressive strength of the actual sample. These results show that the synergistic effect of cortex and medulla can improve mechanical resistance of the rachis. Therefore, the best position (N3) of the primary flight feather shaft can be applied to the bionic design of thin wall structures for energy absorption. This research can provide some guidance for the application of lightweight structural design. RESEARCH HIGHLIGHTS: The internal structure of bean goose feather shaft was observed by micro-CT. The experimental method has a deeper understanding of the compressive properties of rachis fiber orientation. Under the synergistic effect of cortex and medulla, the compressive performance of rachis is better.

Effects of clipping of flight feathers on resource use in Gallus gallus domesticus.

Ground-dwelling species of birds, such as domestic chickens (Gallus gallus domesticus), experience difficulties sustaining flight due to high wing loading. This limited flight ability may be exacerbated by loss of flight feathers that is prevalent among egg-laying chickens. Despite this, chickens housed in aviary style systems need to use flight to access essential resources stacked in vertical tiers. To understand the impact of flight feather loss on chickens' ability to access elevated resources, we clipped primary and secondary flight feathers for two hen strains (brown-feathered and white-feathered, n = 120), and recorded the time hens spent at elevated resources (feeders, nest-boxes). Results showed that flight feather clipping significantly reduced the percentage of time that hens spent at elevated resources compared to ground resources. When clipping both primary and secondary flight feathers, all hens exhibited greater than or equal to 38% reduction in time spent at elevated resources. When clipping only primary flight feathers, brown-feathered hens saw a greater than 50% reduction in time spent at elevated nest-boxes. Additionally, brown-feathered hens scarcely used the elevated feeder regardless of treatment. Clipping of flight feathers altered the amount of time hens spent at elevated resources, highlighting that distribution and accessibility of resources is an important consideration in commercial housing.

Exceptional Preservation of Feather Micro-Structures in Amber from the Middle-Cretaceous of Myanmar

Feathers are under-represented in the fossil record because soft tissues do not usually preserve well in sedimentary sequences. Fossil feathers are nevertheless extremely important in resolving pattern and process related to the origin of dinosaur flight. In recent years, a number of feathers have been discovered which have been mummified in amber; these feathers are preserved in three dimensions with remarkable sub-microscopic details and are especially important for our understanding of the early development of feathers. In this paper, we describe a diverse assemblage of mid-Cretaceous feathers contained within seven pieces of amber that have been recovered from northern Myanmar (Burma). These pieces include pennaceous primary feathers, contour feathers, and rachis-dominated feathers, and also a plumulaceous (downy) feather. Subcomponents of these feathers, such as barbs, barbules, and nodes are immediately recognizable. One extraordinary piece contains the distal remains of the first four primary flight feathers and a small number of possible hooklets. These pieces are discussed in terms of evolutionary development and comments are made on flight ability where appropriate. These feather-types are classified and compared with similar structures seen in Mesozoic and extant birds. We consider that integumentary feathers and ‘feather-like’ structures fall within two major structural categories (‘shafted’ and ‘non-shafted’).

Identification of a unique barb from the dorsal body contour feathers of the Indian Pitta Pitta brachyura (Aves: Passeriformes: Pittidae)

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.

Identification of a unique barb from the dorsal body contour feathers of the Indian Pitta Pitta brachyura (Aves: Passeriformes: Pittidae)

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.

Threshold models improve estimates of molt parameters in datasets with small sample sizes

Abstract The timing of events in birds’ annual cycles is important to understanding life history evolution and response to global climate change. Molt timing is often measured as an index of the sum of grown feather proportion or mass within the primary flight feathers. The distribution of these molt data over time has proven difficult to model with standard linear models. The parameters of interest are at change points in model fit over time, and so least-squares regression models that assume molt is linear violate the assumption of even variance. This has led to the introduction of other nonparametric models to estimate molt parameters. Hinge models directly estimate changes in model fit and have been used in many systems to find change points in data distributions. Here, we apply a hinge model to molt timing, through the introduction of a double-hinge (DH) threshold model. We then examine its performance in comparison to current models using simulated and empirical data. Our results suggest that the Underhill–Zucchini (UZ) and Pimm models perform well under many circumstances and appear to outperform the DH model in datasets with high variance. The DH model outperforms the UZ model at low sample sizes of birds in active molt and shorter molt durations and provides more realistic confidence intervals at smaller sample sizes. The DH model provides a novel addition to the toolkit for estimating molt phenology, expanding the conditions under which molt can accurately be estimated.

Integrity of and damage to wings, feather vanes and serrations in barn owls

The silent flight of owls is well known. It has served as role model for the designs of new airplane wings and ventilators. One of the structural features that underlies silent flight is the serrated leading edge of the wing that is mainly formed by the tenth primary flight feather (P10). We examined here how much the wings, the P10 feather and the serrations in different populations of barn owls reflect the intact situation. First, when the P10 feather molts, no or fewer serrations are present. Furthermore, damage to feathers and serrations may occur. Damage may be due to several factors like broken feather tips, lost rami, barbules, or broken tips of serrations. The latter may cause a narrowing of the outer vane of the P10 feather. We quantitatively assessed damage by counting the number of wings with missing or broken primary feathers, the number of wings with a narrowed outer vane of the P10 feather, and the number of serrations with reduced length. Considerable damage occurred on wings and feathers on both the macroscopic and microscopic levels. The observed damage most likely influences flight performance. More damage occurred in Galapagos barn owls than in North American and European barn owls. The Galapagos population may be more vulnerable than the other populations because it may at least temporarily be in a bad nutritional state and, thus, postpone molt.

Feathers accurately reflect blood mercury at time of feather growth in a songbird

Methylmercury (MeHg) is a globally distributed pollutant that can negatively affect wildlife. Bird feathers are often used as a monitoring tool of contaminant exposure, but variability in total mercury (THg) content in flight feathers has raised concerns over their utility. The objective of this study was to quantify blood and feather THg depuration through the progression of primary feather molt in order to clarify the relationship between blood and feather mercury concentration, and test the reliability of feather THg measurements as a monitoring tool in wild songbirds. Song sparrows (Melospiza melodia) were experimentally exposed to dietary MeHg and their blood and primary feather THg concentrations were measured during exposure and post-exposure periods of three months each. A rapid decrease in feather and blood THg concentration through molt progression was observed. Primary feather THg content was higher in feathers grown during the MeHg exposure period compared to those grown during the post-exposure period. Primary feather THg concentration was highly correlated with blood THg measured at the time of feather growth (R = 0.98), indicating that, although THg concentration is variable among flight feathers, this reflects temporally sequential molting patterns and declining blood concentration during depuration. Primary flight feathers thus provide an accurate and useful tool for estimating the mercury burden of birds at the time a chosen feather was grown, and have the potential to be an effective and reliable biomonitoring tool for species with well-characterized molt patterns.

Body Mass and Primary Molt Patterns of Greater Sage-Grouse in Colorado

Patterns in body mass and molt provide useful information about how birds interact with their environment and act as potential explanatory variables in behavioral and demographic differences among sex and age classes. We collected population data for Greater Sage-Grouse (Centrocercus urophasianus) in Jackson and Moffat counties, Colorado, from 1973 to 1993 prior to consideration of federal listing of the species under the Endangered Species Act. Using spotlights and long-handled nets, we located and captured Greater Sage-Grouse while they roosted (primarily at night). Each captured bird was banded and released near the site of capture. We recorded the molt status of the primary flight feathers (1–10) and measured body mass. Most birds were captured prior to and during breeding (March–May) and during the brood-rearing period (July–September). Replacement of primary (P) flight feathers was initiated in May, starting with the first primary (P1), and was completed at the last primary (P10) by late September for adult (ASY) and subadult (SY) males, and by October for hatch-year males (young of the year, HY). Adult and subadult females did not replace primary flight feathers until after nesting was completed, starting in June. Primaries 1–3 were replaced within a week of the hen leaving the nest site, with or without chicks. Primary replacement then was similar to that of adult and subadult males and was completed before early October. A few late-nesting hens retained P10 and P9 into early October. Young of the year rarely replaced juvenal P9 and P10 in the year of hatching. Body mass of males peaked (x = 3000 g for adults, and 2200 g for yearlings) in March–April when birds were primarily feeding on sagebrush and then decreased to late May and reached seasonal lows (x = 2200 g) in July–August. Mass of females peaked in April (x = 1640 g) and decreased to 1250 g in August.

An unusually large bird wing in mid-Cretaceous Burmese amber

All of the bird specimens previously recovered from Burmese amber have belonged to either immature specimens, or small-bodied taxa belonging to Enantiornithes. This has led to questions about whether the size bias inherent to preservation in amber has limited inclusions to smaller individuals or species, or if the avifauna of the amber-producing forest had a stronger representation of small-bodied taxa than other Cretaceous assemblages. A newly discovered inclusion of a fragmentary bird wing is described here: specimen LV-0321 likely belonged to an individual that was in excess of 10 cm long (snout to vent length). The new specimen also displays more prominent light-and-dark banding patterns among the primary flight feathers than any of the wings previously described from the deposit. In addition to increasing the known size range for enantiornithines within the assemblage, the new specimen sheds further light on the appearance of the plumage in these Cretaceous birds.

The Dynamics of the Replacement of Primary Flight Feathers in Passerine Birds and Possible Synchronization Factors

Abstract—A study was made to investigate the dynamics of the replacement of primary flight feathers in several passerine bird species in natural and laboratory conditions. Birds were kept at different photoperiods or early postbreeding molting was induced in winter by moving birds to a chamber with a 15-h photoperiod, which is efficient for gonadal development. Observations of birds were performed over 5 years for all photoperiods under study; a biorhythm with an approximately 3-day period was detected for the beginning of new flight feather development during molting in passerine birds. A time interval that was a multiple of approximately 3 days was observed between the replacements of adjacent primary flight features under various light–dark schedules (hours): 20 light (L) : 4 dark (D), 17L : 7D, 14L : 10D, and 12L : 12D. The phases of the 3-day biorhythm were compared with the dynamics of external atmospheric and heliogeophysical processes, and the most significant relationship was observed with extremes of changes in the speed of the Earth’s rotation around its axis. The external factors that are influenced by extremes of changes in the Earth’s rotational speed were assumed to act as synchronizers of the biorhythm.

Flight, symmetry and barb angle evolution in the feathers of birds and other dinosaurs.

There has been much discussion over whether basal birds (e.g. Archaeopteryx and Confuciusornis) exhibited active flight. A recent study of barb angles has suggested they likely could not but instead may have exhibited a gliding phase. Pennaceous primary flight feathers were proposed to show significant shifts in barb angle values of relevance to the inference of flight in these extinct taxa. However, evolutionary trends in the evolution of these barb angle traits in extant volant taxa were not analysed in a phylogenetic frame. Neither the ancestral crown avian condition nor the condition in outgroup dinosaurs with symmetrical feathers were assessed. Here, we expand the fossil sample and reanalyse these data in a phylogenetic frame. We show that extant taxa, including strong flyers (e.g. some songbirds), show convergence on trailing barb angles and barb angle asymmetry observed in Mesozoic taxa that were proposed not to be active fliers. Trailing barb angles in these Mesozoic taxa are similar to symmetrical feathers in outgroup dinosaurs, indicating that selective regimes acted to modify primarily the leading-edge barb angles. These trends inform dynamics in feather shape evolution and challenge the notion that barb angle and barb angle ratios in extant birds directly inform the reconstruction of function in extinct stem taxa.

Plumage development and moult in captive Black-bellied Sandgrouse Pterocles orientalis: age and sex variations

The sandgrouse, family Pteroclididae, are a group of birds adapted to open, arid habitats and powerful fliers but information on their plumage development and moult is scarce. In this study, the annual cycle of body plumage development, sequence and duration of primary flight feathers moult were investigated in Black-bellied Sandgrouse Pterocles orientalis, from hatching to the adult stage. Body plumage differed among juvenile, immature and subadult birds before their first breeding season. Yearling Black-bellied Sandgrouse showed three annual moults with only the pre-breeding one being complete. Juvenal body plumage was acquired shortly before the first attempts to fly at 5–6 weeks of age. The acquisition of definitive adult body plumage took place after the breeding season in late August, when birds were about 10–12 months old. The species typically replaced all primaries annually with a gradual descendent moult at a slow rate, taking 10–11 months for their completion, from December to September, including the breeding period. This study provides the first detailed analysis of flight feather development and moulting in the Black-bellied Sandgrouse, which provides useful ageing criteria based on the patterns of both primary growth and moult.