Flight Feathers Research Articles

Using generalised additive models to visualise the annual cycle of primary feather moult patterns

Moult is a vital but energy-demanding event in a bird's phenological cycle. Primary moult is the shedding of old feathers and the regeneration of new flight feathers to maintain efficient functioning of these critical structures. Life history events, such as moult, breeding and migration, are typically separated from one another temporally because of the costs associated with moult Thus, extrapolation of other life-history events is possible from an understanding of the primary moult schedule in species for which data are easier to collect This study aimed to explore the primary moult patterns of nine nectarivorous species (seven Sunbirds and two Sugarbirds) using data extracted from the South African Bird Ringing Unit (SAFRING) database. Logistic generalised additive models (GAMs) were fitted to active/inactive moult observations to explore annual primary moult patterns. Breeding patterns based on the presence of brood patches in females were also analysed using GAMs for species with sufficient data. The GAMs illustrated the annual patterns well, with the probability of moult having clear peaks and troughs, allowing intuitive understanding of annual life-history patterns, such as the probability of breeding. Generally, GAMs hold potential to be used as a supplementary tool to study the timing of primary moult GAMs appear especially useful for species with no well-defined annual moult period.

Colony attendance and moult pattern of Cory's Shearwaters (Calonectris borealis) differing in breeding status and age

Migratory birds must fit three costly life‐history events within the annual cycle, reproduction, moult and migration, to minimize their overlap and maximize survival and breeding success. However, some seabirds, such as Cory's Shearwater Calonectris borealis, overlap body moult and breeding, with flight feather renewal occurring in late chick‐rearing. In contrast, the moult patterns of non‐breeding adult (sabbatical) and immature Cory's Shearwaters, which also attend the colony during the breeding season, remain poorly understood. Furthermore, the potential implications of life‐stage and breeding status trade‐offs on moult status and colony attendance in non‐breeders has rarely been investigated. Surveying different areas within one colony between June and September 2013 and 2014, we studied the age and breeding status composition of birds attending the breeding colony and scored moult of their body (breast and upper‐neck), wing and tail feathers. We found that in addition to breeders (n = 165), 57.6% of the birds (n = 389) attending the colony were 4‐ to 10‐year‐old immatures (n = 132) and adult sabbatical shearwaters (n = 92). Sabbaticals and 8‐ to 10‐year‐old immatures (n = 28) were present at the colony during incubation, whereas only three sabbatical birds and no 8‐ to 10‐year‐old immatures were captured in late chick‐rearing. Conversely, 4‐ to 7‐year‐old immatures arrived later in the season but were still present in late chick‐rearing. Sabbatical and 8‐ to 10‐year‐old immatures were moulting body feathers at the same time as adult breeders, whereas, among 4‐ to 7‐year‐old immatures, older birds moulted earlier than younger birds. A larger proportion of sabbatical birds were replacing tail feathers compared with adult breeders. However, there was no evidence that sabbaticals or 8‐ to 10‐year‐old immatures differed in wing moult from adult breeders until August. Overall, our study shows that colony attendance by non‐breeding adults and immatures is widespread in this population. The synchronous moult schedule of flight and body feathers across age groups at different life‐history stages may suggest that this aspect of moult is controlled by environmental conditions.

Heavy Metals in Wetland Ecosystem: Investigating Metal Contamination in Waterbirds via Primary Feathers and Its Effect on Population and Diversity

Wetlands are dynamic ecosystems that provide feeding and nesting grounds for diverse species of waterbirds. The quality of wetland habitat may have an impact on the density, diversity, and species richness of waterbirds. Toxic metal contamination is one of the most significant threats to wetland habitats. Feathers are a key indicator of heavy metal contamination in avian communities as a non-invasive method. We examined the levels of Arsenic (As), Cadmium (Cd), Cobalt (Co), Chromium (Cr), Copper (Cu), Lead (Pb), Nickel (Ni), and Zinc (Zn) using ICP-AAS and standards of digestion procedure from the primary feathers of 10 distinct species of waterbirds. The study was conducted at four wetlands, viz., Point Calimere Wildlife Sanctuary (Ramsar site); Pallikaranai Marshland (Ramsar site); Perunthottam freshwater lake (unprotected wetland), Tamil Nadu and the Pulicat Lake, Andhra Pradesh, (Ramsar site), India. The Large crested tern had higher concentrations of As, Co, Cr, and Ni. Cu was greater in the Indian pond heron, and Zn was higher in the Grey heron. The accumulation of metals differed among the waterbirds (p < 0.05), and the inter-correlation of metals found positive influences between the tested metals, i.e., Co was positively associated with As, Cr had a positive correlation with As and Co, and Ni was positively correlated with As, Co, Cr, and Cu. In contrast, Pb had a positive association with Cu and Ni. The Zn was associated with Co, Cr and Cu. The level of metals in waterbirds was Zn > Cu > Cr > Ni > Pb > Co > Cd > As. The results showed that metal levels in the primary feathers of waterbirds were greater than the other species of waterbirds examined across the world. Thus, the study emphasizes that managing wetlands and controlling pollution is crucial to saving waterbirds; otherwise, the population and diversity of waterbirds will decline and become a significant threat to waterbird communities.

Reduction of wing area affects estimated stress in the primary flight muscles of chickens.

In flying birds, the pectoralis (PECT) and supracoracoideus (SUPRA) generate most of the power required for flight, while the wing feathers create the aerodynamic forces. However, in domestic laying hens, little is known about the architectural properties of these muscles and the forces the wings produce. As housing space increases for commercial laying hens, understanding these properties is important for assuring safe locomotion. We tested the effects of wing area loss on mass, physiological cross-sectional area (PCSA), and estimated muscle stress (EMS) of the PECT and SUPRA in white-feathered laying hens. Treatments included Unclipped (N = 18), Half-Clipped with primaries removed (N = 18) and Fully-Clipped with the primaries and secondaries removed (N = 18). The mass and PCSA of the PECT and SUPRA did not vary significantly with treatment. Thus, laying hen muscle anatomy may be relatively resistant to changes in external wing morphology. We observed significant differences in EMS among treatments, as Unclipped birds exhibited the greatest EMS. This suggests that intact wings provide the greatest stimulus of external force for the primary flight muscles.

Pattern and intensity of moult in White-capped/Shy Albatrosses Thalassarche steadi/cauta

Albatrosses typically only replace a subset of flight feathers each annual moult cycle. We scored the moult of 662 White-capped/Shy Albatrosses Thalassarche steadi/cauta, using birds that had been killed by longline fisheries off South Africa. Most adults and immatures alternated replacing the outer primaries (phase 1) and inner primaries (phase 2), but there was considerable variation among adults, with 0–10 primaries replaced each moult cycle. Birds in phase 1 moult replaced fewer primaries than birds in phase 2, but the proportion by mass was similar. Adults replaced more primaries than immatures as there was a disproportionate number of adults in phase 2 moult (82%), which might indicate that most adults off South Africa are in their first year after a successful breeding attempt, but a similar bias occurred among beached birds from New Zealand and Australia. The outer primaries were usually replaced outwards from P8, but the replacement sequence was more variable among the inner primaries. Secondary moult overlapped with primary moult, but not all secondaries were moulted each year. Adults had more active moult centres and replaced more secondaries at once than immatures. Tail moult started after primary moult, with 1–11 feathers growing from 1–6 active centres. Some birds replaced their rectrices in pairs, with often 2 or 3 pairs moulting at once, but others replaced alternate feathers or almost all rectrices at once. A few birds exhibited intense wing moult, but the norm was to replace only 1 or 2 primaries and 1–6 secondaries at once. Age- and sex-related differences in moult intensity presumably result from different time constraints. Adult White-capped/Shy Albatrosses take a year off between successful breeding attempts, allowing time for a more protracted moult. However, we cannot explain the intense moult in some immatures. Our findings support recent studies showing that albatross flight feather moult patterns are more varied than previously reported.

A NEST OF CLUB-WINGED MANAKIN MACHAEROPTERUS DELICIOSUS IN NORTHWEST ECUADOR

The Club-winged Manakin Machaeropterus deliciosus is an iconic Pipridae species due to its display behavior, including unique mechanical sounds produced by vibrating modified wing feathers. However, its nesting biology remains poorly known. We present a detailed description of one nest studied in northwest Ecuador in June–July 2021. We provide new information on incubation and maternal care. The nest was a low cup/fork sited on three forks, covered with moss, built 90 cm above the ground and at 50 m distance from a lekking site. The female had high nest attentiveness during the incubation period but decreased markedly in the first nine days post-hatching. The nest produced two juveniles that fledged 16 days after hatching. The breeding biology of this species remains poorly studied, so we recommend further research, including protracted monitoring of nests to understand important aspects of M. deliciosus breeding biology, including incubation period, attendance rates, and nesting success.

A non-invasive feather-based methodology for the detection of blood parasites (Haemosporida)

Blood parasite (haemosporidian) infections are conventionally detected using blood samples; this implies capturing and handling birds to obtain them, which induces stress and causes pain. Feathers have blood vessels, and some blood could be preserved in the feather’s shaft after moulting. We used feather DNA for detecting haemosporidians by PCR testing in diverse scenarios. First, haemosporidian DNA was detected in feathers from carcasses of infected birds, proving the feasibility of the approach. Storage temperature affected DNA recovery, with maximum retrieval and haemosporidian detection at the lowest temperature (− 20 °C). All feather types from infected birds kept at optimal conditions yielded haemosporidian DNA. Parasite detection by PCR was correlated with DNA yield, which was significantly higher in heavier birds, flight feathers, and more feathers per pool. Lastly, haemosporidians were detected employing feathers moulted from wild and captive birds to estimate infection prevalence. We show for the first time that using blood from feather shafts for haemosporidian detection can be an advantageous and less invasive alternative to blood sampling if feathers are optimally preserved. This method could contribute to uncovering haemosporidian infections in endangered and elusive birds, and it might facilitate routine screening in captive birds, thereby improving infection detection, prevention, and control.

Using banding data to estimate primary feather molt and hatch chronology of white‐winged doves in Texas

AbstractBanding data are commonly used to estimate vital rates for migratory game bird management. We used white‐winged dove (Zenaida asiatica) banding data to estimate molt and hatch chronology in Texas. We used Texas Parks and Wildlife Department's long‐term, state‐wide banding data (71,675 banded individuals) from 1 June to 15 August 2007–2016 to investigate primary feather molt and hatching in white‐winged doves in Texas. We estimated primary feather molt and used individual recapture data to determine reliability of models predicting primary feather molt rates. For hatching, we used primary feather molt scores of captured hatch‐year doves to backdate to an estimated hatch date. Our modeling predicted mean after‐hatch‐year primary feather molt rate of 13.21 ± 0.93 days. We predicted 95% of adult white‐winged doves began molting between 7 April to 8 July and completed molt between 17 August to 17 November. Across all years, white‐winged doves hatched as early as 6 January and as late as 27 July, with 95% of all hatching occurring between 22 March and 18 June and peaking on 4 May. Primary feather molt initiation peaked 16 days after the peak of hatching, suggesting that white‐winged doves delay the onset of primary molt until reproductive activity slows. Secondary data collected during banding operations on migratory game birds may be used to understand additional life processes without the requirement to initiate additional survey efforts.

Quill mites of the family Syringophilidae (Acariformes: Prostigmata) parasitising doves of the genus Turtur (Columbiformes: Columbidae)

Mites belonging to the Syringophilidae family are a cosmopolitan and taxonomically diverse group of obligate and permanent parasites. These mites inhabit and reproduce within the hollow quills (calamus) of the wing, tail, and contour feathers. This study presents the first field observations of quill mites parasitising doves of the Turtur genus distributed in sub-Saharan Africa. A total of 145 host individuals from all five Turtur species (i.e., T. abyssinicus, T. afer, T. brehmeri, T. chalcospilos, and T. tympanistria) were examined during ornithological surveys conducted in Ghana, Uganda, Mozambique, and Nigeria. All examined bird species were found to be parasitised by a single oligoxenous syringophilid species, Meitingsunes tympanistria Skoracki & Dabert. Previously, this mite species had only been recorded from T. chalcospilos and T. tympanistria and from Tanzania and Togo; thus, the remaining dove species and countries of origin represent new host and locality records for this quill mite species. In our study, 20 individuals (13.8%) of the Turtur genus were infested by quill mites, with prevalence ranging from 8.8% to 24.2%. Mites were found to inhabit only the quills of wing coverts. No relationship was observed between the host body condition of two analysed host species (T. tympanistria and T. chalcospilos) and infestation by M. tympanistria. The fact that M. tympanistria exploits all representatives of the genus Turtur suggests that this mite species invaded these birds before their radiation, dating back approximately 15 Mya (Middle Miocene).

Research Note: Injection of adenoviral CRISPR/Cas9 system targeting melanophilin gene into different sites of embryos induced regional feather color changes in posthatch quail

Poultry species is an important animal model in both avian research and the poultry industry. To advance our understanding of genetic factors and benefit both fields, a gene of interest can be genetically edited, and consequential phenotypic changes can be investigated. Injection of adenovirus containing the CRISPR/Cas9 system into avian blastoderm induced genome editing in blastodermal cells randomly, including primordial germ cells, which results in generation of whole-body knockout in the offspring of the virus-injected quail. However, to observe phenotypic and functional changes in whole-body, homozygous knockout of genes using this genome editing technology requires at least 2 generations of breeding of chimeric, and heterozygotes birds. In the current study, we developed a strategy to investigate the gene function in 1-generation by inducing regional genome editing around the injection sites with CRISPR/Cas9 adenovirus. The adenoviral CRISPR/Cas9 vector targeting the melanophilin (Mlph) gene, regulating feather pigmentation, was injected into 2 different regions of embryos, the cervical flexure of quail embryos at HH stage 13 to 15 and the tip of the upper limb bud of embryos at HH stage 22 to 24, to induce genome editing in those regions. Indel mutations in the target loci of the Mlph gene were detected by extracting genomic DNA from the embryonic tissues, and consequential phenotypes, feather color changes, were analyzed at 1 mo after hatch. Injection of the adenovirus into the cervical flexure and the tip of the upper limb bud of embryos resulted in 8 to 21% efficiency of indel mutation in the embryonic cells of the injected regions. In the posthatch quail, gray feathers were shown on their upper back and primary wing feathers, corresponding to the injection sites at embryos. Successful validation of this strategy for inducing genome editing in parts of tissues within 1-generation will accelerate studies on genetic functions with advantages of less time and cost, facilitating avian research and providing foundations for future application for the poultry industry.

The first ecological contamination study of avian mercury and lead in southeast Iran, Hamun International Wetlands.

The concentrations of mercury (Hg) and lead (Pb) in feather samples of nine bird's species (n = 65) were determined from southeastern areas of Iran, Hamun International Wetlands. Hg concentrations were ranged from 0.40 to 3.00 mg/kg dry wt and from 0.38 to 1.76 mg/kg for primary and secondary feathers, respectively. Furthermore, Pb concentrations were ranged from 1.43 to 4.10 mg/kg and from 1.28 to 3.65 mg/kg for primary and secondary feathers, respectively. Deposition of metals varied significantly among the primary and secondary feathers of systematic category (families) for Hg and Pb (p < 0.001). It was found that there is a significant difference in feather Hg and Pb concentrations across species (p < 0.001) with highest concentrations in saker falcon (Falconidae) (Hg = 3.00 mg/kg and Pb = 4.10 mg/kg, primary feather) followed by little owl (Strigidae). Grey francolin (Phasianidae) contained the least amount of Hg (0.40 mg/kg) and Pb (1.43 mg/kg) in primary feather. The results showed that the highest concentrations of heavy metals were related to carnivores. Fish predators, omnivores, and insectivores were examined at the next level of metal concentration, with herbivores having the lowest concentrations of lead (1.43 mg/kg) and mercury (0.40 mg/kg). Birds with an open grasslands feeding strategy had the highest mercury and lead concentration. The average value for Pb was on the border of harmful effects (4 mg/kg). The results of this study indicate that mercury levels are lower than the threshold level for reproductive and behavioral harm (5 mg/kg).

The Defeathering Effect by Scalding in Chickens Follows Their Intrinsic Dermal Histologies.

This study aimed to delineate the fundamental skin histology and its association with feathers in broilers and native Red-Feather (RF) chickens and further elucidate their thermal alterations in respect to the defeathering effect by scalding. Comparisons of skin thickness between fresh samples and those after dehydration and fixation, as well as their collagen contents and histological differences, suggested that RF chickens had a thicker dermal layer with more collagen deposition and compact architecture, particularly in the neck and abdominal skin, but a thinner hypodermal layer in the back, chest, and abdomen skin. Despite an adolescent age, RF chickens showed a shorter calamus depth of tail feathers but a larger calamus diameter of wing feathers. Within the feather follicle punch, a very intense follicle sheath layer with compact collagenous matrixes to fulfill the space next to the inner feather root sheath was observed in RF chickens. Under both soft and hard scalding, RF chickens showed a lower degree of denaturation on hip skins and were more resistant to structural disintegration, primarily within the epidermal and dermal layer. Accordingly, a much narrower gap space between the feather sheath and surrounding follicle sheath was observed, and the gap expansion was also resistant to thermal changes. These results suggest that the defeathering effect by scalding follows the intrinsic skin histologies in chickens of various breeds and ages, primarily depending on the interaction of the feather calamus with the surrounding follicle sheath and neighboring cutaneous tissues, reflecting their resistance to thermal denaturation, but is irrelevant to the feathers per se.

PHEROMONE COMMUNICATION IN FEATHER-FEEDING WING LICE (INSECTA: PHTHIRAPTERA).

Pheromone communication is central to the life history of insect parasites. Determining how pheromones affect parasite behavior can provide insights into host-parasite interactions and suggest novel avenues for parasite control. Lice infest thousands of bird and mammal species and feed on the host's feathers or blood. Despite the pervasiveness of lice in wild populations and the costs they exact on livestock and poultry industries, little is known about pheromone communication in this diverse group. Here, we test for pheromone communication in the wing lice (Columbicola columbae) of Rock Doves (Columba livia). Wing lice spend the majority of their lives on bird flight feathers where they hide from host preening by inserting their bodies between coarse feather barbs. To feed, wing lice must migrate to bird body regions where they consume the insulating barbs of contour feathers. We first show that wing lice readily form aggregations on flight feathers. Next, using a Y-tube olfactometer, we demonstrate that wing lice use pheromone communication to move toward groups of nearby conspecifics. This pheromone is likely an aggregation pheromone, as wing lice only produce the pheromone when placed on flight feathers. Finally, we found that when forced to choose between groups of male and female lice, male lice move toward male groups and females toward female groups, suggesting the use of multiple pheromones. Ongoing work aims to determine the chemical identity and function of these pheromones.

Numerical investigation of non-planarity and relative motion for bionic slotted wings

Bird wings have split primary feathers that extend out from the wing surface. This structure is called the wingtip slot, which is recognized as a product of bird evolution to improve flight performance. In this paper, numerical simulations based on RANS (Reynolds-averaged Navier–Stokes) equations are conducted to examine and understand the influence of wingtip slots on six wings at Re = 100 000. The overlapping grid method, driven by an in-house UDF (User Defined Function), is used to model the motion of the bionic slotted wings. The motion law of the winglets is improved based on the law extracted from a level-flying bald eagle. Then the aerodynamic force, pressure distribution, vorticity contours, wake stream, and other flow structures of the slotted wings with different layouts were compared and analyzed. The results show a significant increase in aerodynamic force when the slotted wingtips are employed. The maximum lift-to-drag ratio is also improved in our designed wing model with a non-planar wingtip by a maximum of 34% from the base wing. Each winglet works as a single wing due to the existence of slots, with a chordwise pressure distribution similar to that of the main wing. The vortex structures of slotted wings show expressive changes in the tip vortex as compared with the base wing. Additionally, an innovative bionic slotted wing is proposed with a dynamic wingtip that forms varying gaps between winglets. Due to the collective mechanism of aerodynamic interaction among multiple winglets for the innovative wing, it acquires the optimal time-averaged force during a flapping period. As expected, the slotted wingtip reduces the main wingtip vortex intensity and creates weaker vortices. The non-planarity and relative motion of the wingtip strengthen its weakening effect on the wingtip vortex and wake.

Identification of the Greater Spotted Eagle Clanga clanga, Lesser Spotted Eagle Clanga pomarina and interspecific hybrids using the morphology of shed flight feathers

ABSTRACT Capsule Shed feathers can be used for the field identification of the Greater Spotted Eagle Clanga clanga and Lesser Spotted Eagle Clanga pomarina, but identification of hybrids is problematic. Aims To provide an easy method for distinguishing the shed flight feathers of the Greater Spotted Eagle, Lesser Spotted Eagle, and their hybrids. Methods We examined seven morphological characteristics and developed multinomial logistic regression models to aid in identification of feathers. Results The most informative feature was the relative feather length. Barring improved the identification of tail feathers, secondaries, and proximal primaries. Feathers of Lesser Spotted Eagles were significantly shorter and more barred than those of Greater Spotted Eagles. Feathers of hybrids were also highly barred but had an intermediate length. The length from the tip to notch, width of the notch, and specific colouration patterns were also included in the best models for specific feather types. The combination of these characteristics resulted in identification accuracies of 89–97% for Lesser Spotted Eagle feathers and 80–100% for Greater Spotted Eagle feathers. However, all F1-hybrids were incorrectly identified as Greater Spotted or Lesser Spotted Eagles. Conclusion Shed feathers could have potential for the non-invasive field identification of spotted eagle species at nest sites. However, the identification of hybrids based on feathers is difficult due to substantial morphological variation and overlap with parent species.

Covert-inspired flaps: an experimental study to understand the interactions between upperwing and underwing covert feathers

Birds are agile flyers that can maintain flight at high angles of attack (AoA). Such maneuverability is partially enabled by the articulation of wing feathers. Coverts are one of the feather systems that has been observed to deploy simultaneously on both the upper and lower wing sides during flight. This study uses a feather-inspired flap system to investigate the effect of upper and lower side coverts on the aerodynamic forces and moments, as well as examine the interactions between both types of flaps. Results from wind tunnel experiments show that the covert-inspired flaps can modulate lift, drag, and pitching moment. Moreover, simultaneously deflecting covert-inspired flaps on the upper and lower sides of the airfoil exhibit larger force and moment modulation ranges compared to a single-sided flap alone. Data-driven models indicate significant interactions between the upper and lower side flaps, especially during the pre-stall regime for the lift and drag response. The findings from this study are also biologically relevant to the observations of covert feathers deployment during bird flight. Thus, the methods and results summarized here can be used to formulate new hypotheses about the coverts role in bird flight and develop a framework to design covert-inspired flow and flight control devices for engineered vehicles.

Metal Contents in Feathers from Birds (Rhynchopsitta terrisi, and Columba livia) with Different Ecological Niches.

The metal contaminants can be utilized as an ecological tool to analyze niche partition in birds. As environmental contamination biological indicators, essential (Zn, Cu, and Cr) and non-essential (Pb and Cd) metals in the flight feathers of the Maroon-fronted Parrot and Pigeon with different ecological niches were assessed. The feathers of the parrot were gathered at a national park (Parque Nacional Cumbres de Monterrey) and the feathers of pigeons were collected at an urban site, that is, the city of Monterrey, Mexico. An atomic absorption spectrophotometer was used to establish the concentration of metals in the feathers. Zn, Cu, Cr, Pb, and Cd were detected in the two studied samples. The results obtained in this study exhibited an increase in metal concentrations in pigeon feathers with respect to parrot feathers. In conclusion, employing parrot and pigeon feathers comprises an important tool to track trace-metal occurrence in the environment and metal accumulation in birds. This information is crucial to possess in order to minimize exposure to essential metals in species of wild birds with different ecological niches.

EFFECTS OF MYCOPLASMA GALLISEPTICUM INFECTION ON PREENING BEHAVIORS AND FEATHER QUALITY IN HOUSE FINCHES (HAEMORHOUS MEXICANUS).

Infections can have far-reaching sublethal effects on wildlife, including reduced maintenance of external structures. For many wildlife taxa, daily maintenance of external structures (termed preening in birds) is critical to fitness, but few studies have examined how infections alter such maintenance. Mycoplasma gallisepticum is a common pathogen in free-living House Finches (Haemorhous mexicanus), where it causes mycoplasmal conjunctivitis. Despite documented behavioral changes associated with M. gallisepticum infections in finches, no studies have examined how preening behavior may change with infection and how potential differences in preening may affect feather quality. To test this, we experimentally inoculated captive House Finches with M. gallisepticum or a control treatment, and we collected behavioral and feather quality data to detect potential changes in feather maintenance due to infection. We found that finches infected with M. gallisepticum preened significantly less often, and within the infected treatment, birds with the highest conjunctivitis severity preened the least often. However, there was no difference in the quality scores for secondary flight feathers collected from control versus infected birds. We also assayed feather water retention and found that the degree of water retention correlated with our feather quality scores, such that feathers with poor scores retained more water. However, as with quality scores, feather water retention did not differ with infection; this may be due to the controlled environment that the birds experienced while in captivity. Our data suggest that, in addition to sickness behaviors previously observed in finches, M. gallisepticum infection decreases other behaviors critical to survival, such as preening. While the consequences of reduced preening on feather maintenance were not apparent in captive conditions, further work is needed to determine whether House Finches in the wild that are infected with M. gallisepticum experience a fitness cost, such as increases in ectoparasite loads, due to this reduced feather maintenance.

Morphometrics as a Tool for the Species Identification of North American Bald and Golden Eagle Primary Feathers

ABSTRACT Eagle feathers are among the most commonly trafficked items in the illegal wildlife trade in the United States. Although the tail and secondary wing feathers of Bald Eagles (Haliaeetus leucocephalus) and Golden Eagles (Aquila chrysaetos) generally exhibit identifiable patterns by which the species of origin can be determined, there is a lack of data allowing for the morphological identification of the commonly encountered, unpatterned outer primary wing feathers. To test if the shape of the primary feathers differed between the two species, I measured the notch and emargination heights of the outer five primaries (P10–P6) from specimens at the National Fish and Wildlife Forensic Laboratory collection and the National Eagle Repository. Although there was some overlap in lengths of the feather emargination and notch heights of both species, the results demonstrate that measurements of the outermost primaries do allow for the identification of many loose feathers. Overall, Golden Eagle feathers exhibit longer emarginations and notch heights than those of the Bald Eagle. These results will be valuable for law enforcement officials, ornithologists, and anthropologists studying the remains of North American eagles.

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.