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Urbanization drives phenotypic variation in many animal species. This includes behavioral and physiological traits such as activity patterns, aggression, and hormone levels. A current challenge of urban evolutionary ecology is to understand the environmental drivers of phenotypic variation in cities. Moreover, do individuals develop tolerance to urban environmental factors, which underlie adaptative responses and contribute to the evolution of urban populations? Most available evidence comes from correlative studies and rare experiments where a single urban-related environmental factor has been manipulated in the field. Here we present the results of an experiment in which we tested for differences in the glucocorticoid (CORT) response of urban and rural blue tits nestlings (Cyanistes caeruleus) to artificial light at night (ALAN). ALAN has been suggested to alter CORT response in several animal species, but to date no study has investigated whether this effect of ALAN differs between urban and rural populations. Immediately after hatching, urban and forest broods were either exposed to 2 lux of ALAN (using an LED source mounted inside the nestbox) or received no treatment (dark control). The experiment lasted until the chicks fledged. When the chicks were 13 days old plasma samples were collected to measure baseline CORT concentrations, and feather samples to provide an integrative measure of CORT during growth. Forest birds had higher plasma CORT (pCORT) concentrations than their urban counterparts, irrespective of whether they were exposed to ALAN or not. Conversely, we found population-specific responses of feather CORT to ALAN. Specifically, urban birds that received ALAN had increased feather CORT compared with the urban dark controls, while the opposite was true for the forest birds. pCORT concentrations were negatively associated to fledging success, irrespective of population and treatment, while feather CORT was positively associated to fledging success in broods exposed to ALAN, but negatively in the dark control ones. Our results demonstrate that ALAN can play a role in determination of the glucocorticoid phenotype of wild animals, and may thus contribute to phenotypic differences between urban and rural animals.

Color is a phenotypic trait of utmost importance, particularly in birds, which are known for their diverse color signals and color-producing mechanisms including pigment-based colors, light scattering from nanostructured feather tissues and combinations thereof. Bright iridescent plumage colors of hummingbirds are caused by light scattering by an organized array of flattened, pigment organelles, containing air-filled vesicles, called melanosomes. These hollow platelets are organized in multilayer arrays that contain numerous sharp air/melanin refractive index interfaces, producing brilliant iridescent colors. Despite their ecological significance and potential for inspiration of new optical materials, how platelets form and spatially arrange in nanostructures in growing feathers remains unknown. Here, we tested the hypothesis that melanosome formation and organization occurs mostly through passive self-assembly processes by assembling a developmental time series of growing hummingbird feathers using optical and electron microscopy. We show that hummingbird platelets contain air bubbles or vesicles upon their formation in pigment-producing cells, melanocytes. When melanosomes are transferred to neighboring keratinocytes (the cells shaping barbule structure) they drastically expand in size; and variation in this enlargement appears to be driven by physical constraints caused by the placement of the melanosomes within the barbule plate and their proximity to other melanosomes. As the barbule elongates and narrows, polymerizing feather corneous beta-protein orients melanosomes unilaterally, forcing them into a stacked configuration. These results reveal potentially novel forces driving the self-assembly of the nanostructures producing some of the brightest colors in nature.

Synopsis Individuals undergo profound changes throughout their early life as they grow and transition between life-history stages. As a result, the conditions that individuals experience during development can have both immediate and lasting effects on their physiology, behavior, and, ultimately, fitness. In a population of Canada jays in Algonquin Provincial Park, Ontario, Canada, we characterized the diet composition and physiological profile of young jays at three key time points during development (nestling, pre-fledge, and pre-dispersal) by quantifying stable-carbon (δ13C) and -nitrogen (δ15N) isotopes and corticosterone concentrations in feathers. We then investigated the downstream effects of early-life diet composition, feather corticosterone, and environmental conditions on a juvenile’s social status, body condition, and probability of being observed in the fall following hatch. Across the three time points, the diet of Canada jay young was composed primarily of vertebrate tissue and human food with the proportion of these food items increasing as the jays neared dispersal. Feather corticosterone concentrations also shifted across the three time points, decreasing from nestling to pre-dispersal. Dominant juveniles had elevated corticosterone concentrations in their feathers grown pre-dispersal compared with subordinates. High body condition as nestlings was associated with high body condition as juveniles and an increased probability of being observed in the fall. Together, our results demonstrate that nestling physiology and body condition influence the social status and body condition once individuals are independent, with potential long-term consequences on survival and fitness.

This article contributes to the material turn. It shows how an inquiry into the social life of materiality, with distinctive methodologies such as reconstruction and object-led-approaches, changes our understanding of the past. It advances our thinking about the emergence and significance of cross-cultural objects in the context of cultural exchange. The article charts the spectacular rise in importance of feathers in dress during the Renaissance, its relation to collecting practices and relevance well into the seventeenth century. It argues that meanings of featherwork in Europe were influenced by encounters with the Americas, whose artistry sixteenth-century Europeans greatly admired. The dyeing of feathers in multiple colors for headwear and its crafting into intricate shapes turned into a major European fashion trend. Crafts and materials linked to embodied sensory perception and emotional responses. This revises accounts which present this age purely as one of conspicuous consumption designed to celebrate the prestige of rich patrons and instead enquires into how materials interacted with human perception and the mind. Male consumers decisively shaped taste communities. To understand this uncharted and surprising history we need to explore the first age of globalization.

Made available in DSpace on 2021-06-25T12:33:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-11-01 SELVA Society for the Study of Evolution American Ornithology Society Graduate Research Award Provost's Graduate Research Award from the University of Illinois at Chicago Field Museum's H. B. Conover Fund Society of Integrative and Comparative Biology Field Museum Armour Graduate Student Fellowship Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET-Argentina) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) University of Buenos Aires Sonations are sounds that animals produce with structures other than the vocal apparatus for communication. In birds, many sonations are usually produced with modified flight feathers through diverse kinematic mechanisms. For instance, aeroelastic fluttering of feathers produces tonal sound when airflow exceeds a threshold velocity and induces flight feathers to oscillate at a constant frequency. The Fork-tailed flycatcher (Tyrannus savana) is a Neotropical bird with both migratory and year-round resident subspecies that differ in the shape of the outer primary feathers of their wings. By integrating behavioral observations, audio recordings, and high-speed videos, we find that male Fork-tailed flycatchers produce sonations with their outer primary feathers P8-10, and possibly P7. These sounds are produced during different behavioral contexts including: the pre-dawn display, intraspecific territorial disputes, when attacking potential nest predators, and when escaping. By placing feathers in a wind tunnel, we elicited flutter at frequencies that matched the acoustic signature of sounds recorded in the wild, indicating that the kinematic mechanism responsible for sound production is aeroelastic flutter. Video of wild birds indicated that sonations were produced during the downstroke. Finally, the feathers of migratory (T.s.savana) and year-round resident (T.s.monachus) Fork-tailed flycatchers flutter in feather locations that differ in shape between the subspecies, and these shape differences between the subspecies result in sounds produced at different frequencies. Univ Illinois, Dept Biol Sci, 845 West Taylor St,MC066, Chicago, IL 60607 USA SELVA Invest Conservac Neotrop, Diagonal 42a 20-37, Bogota, Colombia Field Museum Nat Hist, Negaunee Integrat Res Ctr, 1400 South Lake Shore Dr, Chicago, IL 60605 USA Univ Buenos Aires, Dept Ecol Genet & Evoluc, Fac Ciencias Exactas & Nat, Inst IEGEBA CONICET UBA, Ciudad Univ,C1428EGA, RA-2160 Buenos Aires, DF, Argentina Univ Estadual Paulista, Inst Biociencias, Dept Zool, Ave 24a,1515, Rio Claro, SP, Brazil Univ Calif Riverside, Dept Evolut Ecol & Organismal Biol, Riverside, CA 92521 USA Univ Estadual Paulista, Inst Biociencias, Dept Zool, Ave 24a,1515, Rio Claro, SP, Brazil FAPESP: 2012/17225-2

Owls (Strigiformes) evolved specific adaptations to their nocturnal predatory lifestyle, such as asymmetrical ears, a facial disk, and a feather structure allowing silent flight. Owls also share some traits with diurnal raptors and other nocturnal birds, such as cryptic plumage patterns, reversed sexual size dimorphism, and acute vision and hearing. The genetic basis of some of these adaptations to a nocturnal predatory lifestyle has been studied by candidate gene approaches but rarely with genome-wide scans. Here, we used a genome-wide comparative analysis to test for selection in the early history of the owls. We estimated the substitution rates in the coding regions of 20 bird genomes, including 11 owls of which five were newly sequenced. Then, we tested for functional overrepresentation across the genes that showed signals of selection. In the ancestral branch of the owls, we found traces of positive selection in the evolution of genes functionally related to visual perception, especially to phototransduction, and to chromosome packaging. Several genes that have been previously linked to acoustic perception, circadian rhythm, and feather structure also showed signals of an accelerated evolution in the origin of the owls. We discuss the functions of the genes under positive selection and their putative association with the adaptation to the nocturnal predatory lifestyle of the owls.

Variation in rachis (central shaft) morphology in individual remiges (flight feathers) within and among species reflects adaptations to requirements imposed by aerodynamic forces, but the fine-scale variation of feather morphology across remiges is not well known. Here we describe how the shape of the rachis, expressed by the height/width ratio, changes along the longitudinal and lateral axis of the wing in four bird species with different flight styles: flapping-soaring (white storks), flapping-gliding (common buzzards), passerine-type (house sparrows) and continuous flapping (pygmy cormorants). Overall, in each wing feather, irrespective of species identity, rachis shape changed from circular to rectangular, from the base towards the feather tip. The ratio between the height and width of the calamus was similar across remiges in all species, whereas the ratio at the base, middle and tip of the rachis changed among flight feathers and species. In distal primaries of white storks and common buzzards, the ratio decreased along the feather shaft, indicating a depressed (wider than high) rachis cross section towards the feather tip, whereas the inner primaries and secondaries became compressed (higher than wide). In house sparrows, the rachis was compressed in each of the measurement points, except at the distal segment of the two outermost primary feathers. Finally, in pygmy cormorants, the width exceeds the height at each measurement point, except at the calamus. Our results may reflect the resistance of the rachis to in-plane and out-of-plane aerodynamic forces that vary across remiges and across study species. A link between rachis shape and resistance to bending from aerodynamic forces is further indicated by the change of the second moment of areas along the wing axes.

Synopsis Owls have specialized feather features hypothesized to reduce sound produced during flight. One of these features is the velvet, a structure composed of elongated filaments termed pennulae that project dorsally from the upper surface of wing and tail feathers. There are two hypotheses of how the velvet functions to reduce sound. According to the aerodynamic noise hypothesis, the velvet reduces sound produced by aerodynamic processes, such as turbulence development on the surface of the wing. Alternatively, under the structural noise hypothesis, the velvet reduces frictional noise produced when two feathers rub together. The aerodynamic noise hypothesis predicts impairing the velvet will increase aerodynamic flight sounds predominantly at low frequency, since turbulence formation predominantly generates low frequency sound; and that changes in sound levels will occur predominantly during the downstroke, when aerodynamic forces are greatest. Conversely, the frictional noise hypothesis predicts impairing the velvet will cause a broadband (i.e., across all frequencies) increase in flight sounds, since frictional sounds are broadband; and that changes in sound levels will occur during the upstroke, when the wing feathers rub against each other the most. Here, we tested these hypotheses by impairing with hairspray the velvet on inner wing feathers (P1-S4) of 13 live barn owls (Tyto alba) and measuring the sound produced between 0.1 and 16 kHz during flapping flight. Relative to control flights, impairing the velvet increased sound produced across the entire frequency range (i.e., the effect was broadband) and the upstroke increased more than the downstroke, such that the upstroke of manipulated birds was louder than the downstroke, supporting the frictional noise hypothesis. Our results suggest that a substantial amount of bird flight sound is produced by feathers rubbing against feathers during flapping flight.

Synopsis The shape of remiges (primary and secondary feathers) is constrained and stereotyped by the demands of flight, but members of the subfamily of New World ground doves (Peristerinae) possess many atypical remex shapes with which they produce sonations of alarm. Within the genus Columbina specifically, the seventh primary feathers (P7) have elongated barbs that create a protrusion on the trailing vane which varies in size and shape between species. These feathers are hypothesized to have been coopted to produce communicative sounds (i.e., sonations) during flight, but the mechanism of this sound production is unknown. We tested the sound-producing capabilities of spread wing specimens from three species of ground doves (C. inca, C. passerina, and C. talpacoti) in a wind tunnel. High speed video and audio analyses indicated that all wings of adult birds produced buzzing sounds in the orientation and flow velocity of mid-upstroke. These buzzing sounds were produced as the protrusion of elongated barbs fluttered and collided with adjacent P6 feathers at a fundamental frequency of 200 and 400 Hz, respectively. Wings from juvenile C. inca produced significantly quieter buzzes and most (three of four individuals) lacked the elongated barbs that are present in adults. Buzzing sounds produced in the wind tunnel were similar to those produced by wild birds indicating that these P7 feathers have been coopted to produce acoustic signals (sonations) during flight. The shape and mechanism of sound production described here in Columbina appear to be unique among birds.

Within the context of complex sexual signaling, most research has focused on exploring the associations between several signals and/or their relationships with different proxies of individual quality. However, very few studies have focused on checking whether the expression of one signal is conditioned by the expression of the others. Here, by experimentally shortening the throat feathers of male spotless starlings (Sturnus unicolor), we evaluated the influence of this trait on the color expression of the beak base. In addition, we tested the relationship between these two sexually dimorphic characters with traits indicating individual qualities, such as body condition and color reflectance at the wavelength related to carotenes in the tip of the beak. Our results show that the coloration of the beak base in males, but not in females, is positively related to body condition and to the length of ornamental throat feathers. Moreover, the experimental shortening of throat feathers in males had a negative effect on the blue chroma intensity of their beak base 1 year after manipulation. These results support for the first time a causal link between the expression of two sexually dimorphic characters, which is essential to understand their functionality in a multiple signaling framework.

The Jianchang duck is mainly distributed in Southwest China, and has the characteristics of fast growth rate and strong abilities in lipid deposition in the liver. In order to investigate the effects of domestication process on formation of the unique characteristics of Jianchang duck, the whole genome of sixteen individuals and three pooling of Jianchang duck were re-sequenced, and genome data of 70 mallards and 83 domestic ducks from thirteen different places in China were obtained from NCBI. The population stratification and evolution analysis showed gene exchanges existed between the Jianchang and other domestic duck populations, as well as Jianchang ducks and mallards. Genomic comparison between mallards and Jianchang ducks showed genes, including CNTN1, CHRNA9, and SHANK2, which is involved in brain and nerve development, experienced strong positive selection in the process of Jianchang duck domestication. The genomic comparison between Jianchang and domestic duck populations showed that HSD17B12 and ESM1, which affect lipid metabolism, experienced strong positive selection during the domestication process. FST analysis among populations of Jianchang duck with different plumage colors indicated that MITF was related to the phenotype of a white feather, while MC1R was related to the phenotype of hemp feather. Our results provided a base for the domestication process of Jianchang duck and the genomic genes for unique traits.

The authors introduce emotional ability similarity to explain consumer satisfaction in interactions with frontline sales and service employees and other consumers beyond the effects of traditional relational variables in the similarity–attraction paradigm. Four studies examine how and why similar abilities for using emotional information between two people promote relational success in marketplace exchanges. We find that, when interacting with others, consumers who exchange nonverbal information with their partners experience (dis)similarity in their emotional ability (EA). Similar dyads who rely on expressive (high–high EA pairs) or inexpressive (low–low EA pairs) emotion norms experience significantly greater satisfaction in their interactions than consumers with dissimilar norms (high–low EA pairs). Together, these findings advance the understanding of consumer relationships and satisfaction by establishing EA similarity as a new avenue for consumer research.

Most studies on the processes driving evolutionary diversification highlight the importance of genetic drift in geographical isolation and natural selection across ecological gradients. Direct interactions among related species have received much less attention, but they can lead to character displacement, with recent research identifying patterns of displacement attributed to either ecological or reproductive processes. Together, these processes could explain complex, trait-specific patterns of diversification. Few studies, however, have examined the possible effects of these processes together or compared the divergence in multiple traits between interacting species among contact zones. Here, we show how traits of two Pogoniulus tinkerbird species vary among regions across sub-Saharan Africa. However, in addition to variation between regions consistent with divergence in refugial isolation, both song and morphology diverge between the species where they coexist. In West Africa, where the species are more similar in plumage, there is possible competitive or reproductive exclusion. In Central and East Africa, patterns of variation are consistent with agonistic character displacement. Molecular analyses support the hypothesis that differences in the age of interaction among regions can explain why species have evolved phenotypic differences and coexist in some regions but not others. Our findings suggest that competitive interactions between species and the time spent interacting, in addition to the time spent in refugial isolation, play important roles in explaining patterns of species diversification.

Closely related species often differ in coloration. Understanding the mechanistic bases of such differences can reveal whether evolutionary changes in colour are driven by single key mechanisms or changes in multiple pathways. Non-iridescent structural plumage colours in birds are a good model in which to test these questions. These colours result from light absorption by pigments, light scattering by the medullary spongy layer (a nanostructure found within barbs) and contributions from other structural elements. Fairy-wrens (Malurus spp.) are a small clade of closely related birds that display a large diversity of ornamental structural colours. Using spectrometry, electron microscopy and Fourier analysis, we show that 30 structural colours, varying from ultraviolet to blue and purple, share a similar barb morphology. Despite this similarity, we find that at the microscopic scale, variation across multiple structural elements, including the size and density of the keratin cortex, spongy layer and melanin, explains colour diversity. These independent axes of morphological variation together account for sizeable amounts of structural colour variability (R2 = 0.21–0.65). The coexistence of many independent, evolutionarily labile mechanisms that generate colour variation suggests that the diversity of structural colours in this clade could be mediated by many independent genetic and environmental factors.

Despite several high-profile cases of cooperation between sanctioned states, little is understood about how being sanctioned affects target states’ incentives to cooperate with one another and what forms that cooperation might take. I theorize that sanctioned states will tend to seek out sanctions-surviving assistance from nonsanctioned states in most cases. Being sanctioned constrains how much useful assistance that sanctioned states can provide to one another, as they suffer from similar trade constraints, levels of economic turmoil, and governmental resource limitations. I test my theory's predictions that sanctioned states are less likely to cooperate with one another via two different large-n tests involving cooperation via engaging in trade-based sanctions-busting and civil nuclear cooperation. Both of these distinct tests provide strong support for my theory. The final portion of the study conducts an exploratory analysis of why sanctioned states still sometimes cooperate with one another, finding that such cooperation may involve risky or taboo transactions, like arms sales, and that sanctioned parties have incentives to keep their cooperation a secret in such cases. These findings improve our understanding of the various cooperative strategies that states employ to survive sanctions.

Do birds detect and respond to forces acting on feathers through filoplumes, which appear to be unique mechanosensory feathers? If filoplumes function as sensors, their morphology should covary with the morphology of their companion feather to better detect feather movements and position. We explore covariation in filoplumes and primaries across 5 species of birds that vary in body size, molt strategy, and the functional life span of their primaries (Green-winged Teal [Anas crecca], Ring-billed Gull [Larus delawarensis], Turkey Vulture [Cathartes aura], Red-tailed Hawk [Buteo jamaicensis], and Red-winged Blackbird [Agelaius phoeniceus]). Filoplumes never extended beyond the coverts and inserted immediately adjacent to the base of their companion primaries, positioning them to detect subtle changes in feather vibration or movement. Far more variation in filoplume number and morphology was due to species differences than to individuals or position in the wing. Across species, filoplume length and number increased with calamus length of primaries. In the 2 species with growing primaries, the number and length of filoplumes were only weakly associated with molting primaries, suggesting that filoplumes were not replaced when their companion primary was replaced. Further, filoplumes associated with a growing primary were not replaced synchronously, leaving others to sense primary position and movement. Finally, filoplume number and length were greatest in Red-tailed Hawks, a species that carries individual feathers for multiple years, but links between filoplume morphology and molt strategy await broader comparative studies. Taken together, the morphology of filoplumes and their replacement schedule relative to their associated primary suggests that they are sensors, capable of detecting subtle differences in the position and movement of their companion feathers.LAY SUMMARYHow do birds detect and respond to forces acting on feathers, which have no nerves? One idea is through unique mechanosensory feathers called filoplumes.Filoplumes resemble hairs with downy tufts at their tips. They are found immediately adjacent to every contour and flight feather and are thought to transmit information about feather position and movements.We explore links between filoplume morphology and flight feathers in five species of birds. We find that, across species, filoplume morphology matches feather morphology as expected if they function as effective sensors. We also find that the replacement of filoplumes is staggered and not strongly tied to their companion feather, which would allow for the overall sensory function to be maintained.Our findings support the idea that filoplumes may function as sensors of feather position and condition. If these suppositions hold, we predict strong associations between flight ecology, molt strategy, and filoplume morphology.

The Crest mutation in chicken shows incomplete dominance and causes a spectacular phenotype in which the small feathers normally present on the head are replaced by much larger feathers normally present only in dorsal skin. Using whole-genome sequencing, we show that the crest phenotype is caused by a 195 bp duplication of an evolutionarily conserved sequence located in the intron of HOXC10 on chromosome 33. A diagnostic test showed that the duplication was present in all 54 crested chickens representing eight breeds and absent from all 433 non-crested chickens representing 214 populations. The mutation causes ectopic expression of at least five closely linked HOXC genes, including HOXC10, in cranial skin of crested chickens. The result is consistent with the interpretation that the crest feathers are caused by an altered body region identity. The upregulated HOXC gene expression is expanded to skull tissue of Polish chickens showing a large crest often associated with cerebral hernia, but not in Silkie chickens characterized by a small crest, both homozygous for the duplication. Thus, the 195 bp duplication is required for the development of a large crest and susceptibility to cerebral hernia because only crested chicken show this malformation. However, this mutation is not sufficient to cause herniation because this malformation is not present in breeds with a small crest, like Silkie chickens.

Rapid high-intensity molt of flight feathers occurs in many bird species and can have several detrimental consequences, including reductions in flight capabilities, foraging performance, parental care, and plumage quality. Many migratory New World warblers (family Parulidae) are known to have intense remigial molt, and recent work has suggested that simultaneous replacement of the rectrices may be widespread in the family as well. However, the phylogenetic distribution of simultaneous rectrix molt, and high-intensity flight feather molt more generally, has not been systematically investigated in warblers. We addressed this issue by examining flight feather molt in 13 species, representing 7 different warbler genera, at Powdermill Avian Research Center in southwestern Pennsylvania, USA. All 13 species replaced their 12 rectrices simultaneously, with the onset of rectrix molt occurring in the early-middle stages of high-intensity primary molt. As expected, single-brooded early migrants molted earlier than double-brooded species whose nesting activities extend into late summer. However, our finding that late-molting species replaced their primaries more slowly and less intensively than early molting species was unexpected, as late-molting species are widely hypothesized to be under stronger migration-related time constraints. This surprising result appears to be at least partially explained by a positive association between the pace of molt and daylength; shorter late-summer days may mandate reduced daily food intake, lower molt intensity, and a slower pace of molt. In comparison to other passerines, flight feather molt in warblers of eastern North America is extraordinarily intense; at its peak, individuals are simultaneously replacing 50–67% of their 48 flight feathers (all 12 rectrices and 6–10 remiges on each wing) for 2–3 weeks or more. Because molt of this intensity is likely to present numerous challenges for flight, avoiding predators, foraging, and parental care, the period of flight feather molt for warblers constitutes a highly demanding phase of their annual cycle.

Bank Swallows (Riparia riparia) breed naturally in riparian habitats but also at inland human-made aggregate pits. Based on three endogenous markers used to track diet, we demonstrate that inland nesting results in nutritional consequences for young birds due to reduced provisioning of omega-3 fatty acids., The Bank Swallow (Riparia riparia), a threatened species in Canada, breeds primarily in banks at lakeshores and rivers and in artificial (typically inland) aggregate mining pits. Inland pits may be ecological traps for this species, but relative dietary trade-offs between these two nesting habitats have not been investigated. The availability of aquatic emergent insects at lakeshores may have associated nutritional benefits for growing nestlings due to increased omega-3 fatty acids (FAs) in prey. We compared the diets of juvenile swallows from lakeshore and inland pit sites using assays of stable isotope values (δ13C, δ15N, δ2H) of feathers, faecal DNA metabarcoding and blood plasma FAs. Colony proximity to Lake Erie influenced the use of aquatic versus terrestrial insects by Bank Swallow adults and juveniles. Feather δ2H was particularly useful as a tracer of aquatic emergent versus terrestrial prey, and inland juveniles had feathers enriched in 2H, reflective of diets composed of fewer aquatic emergent insects. DNA metabarcoding of juvenile and adult faecal material indicated that lakeshore birds consumed more aquatic-emergent chironomids than inland birds. Lakeshore juveniles had elevated plasma omega-3 eicosapentaenoic acid levels compared with inland pit-breeding birds. We discuss the need to consider ‘nutritional landscapes’ and the importance of this concept in conservation of declining species and populations.

The two most economically important poultry ectoparasites are the northern fowl mite, Ornithonyssus sylviarum (Canestrini and Fanzago), and the poultry red mite, Dermanyssus gallinae (De Geer). Both mites are obligate blood feeders but differ in where they reside. Sampling methods thus focus on-host, especially the vent feathers, for northern fowl mite and off-host, especially cracks and crevices near the nighttime roosting areas, for poultry red mite. Much remains unknown, however, about the basic biology and ecology of both mites. Here we discuss mite detection, quantification, and decision making and provide thoughts on future directions for research.

Birds exhibit remarkable variation in plumage patterns, both within individual feathers and among plumage patches. Differences in the size, shape, and location of pigments and structural colors comprise important visual signals involved in mate choice, social signaling, camouflage, and many other functions. While ornithologists have studied plumage patterns for centuries, recent technological advances in digital image acquisition and processing have transformed pattern quantification methods, enabling comprehensive, detailed datasets of pattern phenotypes that were heretofore inaccessible. In this review, we synthesize recent and classic studies of plumage patterns at different evolutionary and organismal scales and discuss the various roles that plumage patterns play in avian biology. We dissect the role of plumage patches as signals within and among species. We also consider the evolutionary history of plumage patterns, including phylogenetic comparative studies and evolutionary developmental research of the genetic architecture underlying plumage patterns. We also survey an expanding toolbox of new methods that characterize and quantify the size, shape, and distribution of plumage patches. Finally, we provide a worked example to illustrate a potential workflow with dorsal plumage patterns among subspecies of the Horned Lark (Eremophila alpestris) in western North America. Studies of plumage patterning and coloration have played a prominent role in ornithology thus far, and recent methodological and conceptual advances have opened new avenues of research on the ecological functions and evolutionary origins of plumage patterns in birds.LAY SUMMARYBirds have many different plumage patterns that arise from coloration motifs within feathers as well as differences in color among body regions.Plumage patterns play various roles in bird biology. They are involved in mate choice and territoriality, social interactions, camouflage from predators, and many other functions.There is a rich history of detailed study on plumage patterns, which we review and synthesize in this manuscript.Recent advances in photography and image processing algorithms have opened new avenues of research on plumage patterns. These open-source methods enable efficient, repeatable, and scalable analytical pipelines.We illustrate one possible pipeline with a worked example of geographic variation in dorsal plumage patterns among populations of Horned Lark (Eremophila alpestris) in the western United States.Looking ahead, enhanced capacity and scalability for digital photography analyses will reveal new discoveries regarding the ecology and evolution of avian plumage patterns.

Using the patterns of fault bars in their primaries, we studied the mode of primary replacement in non-molting Lesser Sandhill Cranes (Antigone c. canadensis) salvaged from hunters in southwestern Saskatchewan. About 80% of their primaries are used for 2 yr and 20% for 3 yr. Primaries are replaced during the breeding season and are lost in synchronous blocks representing about half the primaries, suggesting that most adults probably can fly weakly during flight feather replacement. Cranes are large, aggressive birds, and this interesting, and undescribed mode of flight feather replacement seems adapted to the ability of adult cranes to defend their precocial chicks from predators. Strikingly, juvenile Sandhill Cranes showed no fault marks in their primaries, suggesting that their parents' ability to protect them shields them from the fright of predator attacks, which, in most birds, causes fault bars to be more prevalent and strongly expressed in juveniles than adults. Adults show interesting variation in the number of primaries replaced annually, which seems likely related to whether or not they are caring for chicks. Further, single primaries may or may not be replaced preferentially, suggesting sensitivity to feather function. Evaluating these observations must await field studies of molting adults.LAY SUMMARYLesser Sandhill Cranes that breed in the far north replace about half of their primaries annually in a synchronous moltThis resolves 2 time period conflicts: the exponential increase with body size in the time required to molt, and the need to overlap primary molt with parental care.Using fault marks, feather growth rates, and feather wear, we deciphered this previously unknown mode of primary replacement from a sample of non-molting birds.Within adjacent blocks of same-age primaries, distance differences from feather tip to marker faults showed that feather pairs were usually lost within 24 hr of each other.Cranes are big, tough birds, and synchronous loss of about half of the primaries helps parents defend young from formidable predators.Synchronous replacement also reduces molt duration to the time required to grow the longest renewed primary, squeezing primary renewal of this far-northern breeder into the brief time window before their long southward migration.

Like all animals, the red fox uses chemical signals for social communication. The supracaudal or tail gland smells of violets, attributed to the presence of carotenoid degradation products, or apocarotenoids, which commonly occur as aromatics in flowers. We have more fully characterized the scent chemistry of the fox tail gland. Volatile chemicals were analyzed by gas chromatography-mass spectrometry (GC-MS) and identified from their electron ionization mass spectra and Kovats retention indices. The 3 previously reported apocarotenoids were confirmed, and many additional compounds found. These include the apocarotenoids β-cyclocitral, β-homocitral, β-ionone, cyclic β-ionone, β-ionone-5,6-epoxide, α-ionene, α-ionone, 2,6,6-trimethylcyclohexanone (IUPAC 2,2,6-), 2,6,6-trimethyl-2-cyclohexen-1-one, 6-methyl-5-hepten-2-one (sulcatone), and geranyl acetone. Notably, sulcatone is a semiochemical in several species. 3,3-Dimethyl-2,7-octanedione was identified as a probable apocarotenoid which is likely to be a significant fox scent chemical. The γ-lactone of 4-hydroxyhexadecanoic acid (hexadecan-4-olide) was also found, one of a group of known mammalian signaling compounds. This rich mixture of volatile apocarotenoids implies an adequate consumption of plant carotenoids, which are known to be necessary for optimal health. Dietary carotenoids color the skin and feathers of some birds, used as a visual signal to conspecifics, and the floral aroma of the fox tail gland may provide an olfactory signal to other foxes.

Gloger's rule is a classic ecogeographical principle that, in its simplest version, predicts animals should be darker in warmer and wetter climates. In a rarely tested more complex version, it also predicts animals should be more rufous in warmer and drier climates. The Variable Antshrike (Thamnophilus caerulescens) is a widely distributed South American passerine that presents an impressive amount of plumage color variation and occupies a wide variety of climatic conditions. Moreover, genetic and vocal evidence indicate ongoing hybridization in south-central Bolivia among 3 populations with very distinct plumages. We collected color data from 232 specimens from throughout this species' distribution to test the predictions of Gloger's rule. We found a negative correlation between brightness and precipitation, consistent with the simple version of Gloger's rule. In contrast, we found that birds were darker in cooler climates, contrary to the simple version of Gloger's rule, but consistent with recent findings in other taxa. We found support for both predictions of the complex Gloger's rule and suggest it might be driven by background matching. We conclude by concurring with a recent suggestion that the simple version of Gloger's rule should be reformulated exclusively in terms of humidity.LAY SUMMARYAlmost 200 years ago, the German naturalist Constantin Gloger predicted that birds that live in warm and rainy areas tend to be darker than those that in live in cool and dry areas. He also predicted that birds tend to be browner when they live in dry areas. This pattern has come to be known as Gloger's rule.South America has the world's greatest bird diversity, but Gloger's rule has almost never been studied in South American birds. This is an important question to address because it can help us learn about how species evolve respond to their environments. It becomes even more important in our era of human-induced climatic changes.We studied Gloger's rule in the aptly named Variable Antshrike. This small South American bird species varies geographically in color from almost all black to almost all white. We used a technique called reflectance spectrophotometry, which allows us to precisely quantify the colors of feathers. We measured over 200 specimens kept in natural history collections. The majority of those specimens were collected by one of us (Brumfield) in Bolivia in the early 2000s. This is the largest sample size ever used to study Gloger's rule in a tropical bird.As predicted by Gloger, we found that the Variable Antshrike tends to be darker in rainier areas, and it tends to be browner in drier and warmer areas. But contrary to Gloger's ideas, we found that it tends to be darker in cooler, not warmer, areas. We suggest that this might be because being dark in cooler places helps birds maintain warm body temperatures. We also suggest that being brown in dry areas helps the birds camouflage amidst sparse vegetation.

The selection pressures that drive flight feather morphology are poorly understood. Using a phylogenetic comparative approach and data from 178 species of birds, we investigated whether both position along the wing length and flight feather length affected vane structure. We found that barb density was lower on distal primaries than on proximal primaries of the leading feather vane. In contrast, on the trailing vane only mid-point barb density differed and, here, it showed denser barbs on the distal primaries. This difference was greater at the feather base than at the tip. Barb angle was higher along the full length of the leading edge vane on the proximal primaries than on the distal primaries. Overall, barb density decreased from base to tip on both trailing and leading vanes on both the proximal and the distal primaries. In general, barb angle was less acute at the feather base than at the tip. Barbs were in general denser in continuous flapping fliers than in soarers and the angle of barbs on both the proximal and the distal primaries was affected by flight type. However, we did not identify consistent differences in the pattern of barb angle change among flight style groups. These findings add new perspectives to our understanding of the functional morphology of the flight feather vane, although we still have limited knowledge on how aerodynamic forces, particularly during take-off and landing, affect the morphology of the feather vane. (Less)

The pace of life history events varies with latitude in many taxa. In birds, especially, life history events tend to be protracted in the tropics. This pattern is likely the result of reduced seasonality in resources and changes in trade-offs associated with risk of mortality. In general, animals invest more in reproduction per attempt and less in adult survival at higher latitudes. Feather growth is a major investment that birds make in their own survival, but geographic patterns of feather growth have received very little study. Evidence from separate studies of molt timing in individual species suggests that high-latitude species complete molt faster than tropical birds. Within species, feathers that are grown more quickly tend to show lower structural integrity than feathers grown more slowly, but seasonality of resources may place temporal constraints on the pace of feather growth. I hypothesized that increased seasonality of resources or decreased investment in adult survival in relation to...

Feather diversity is striking in many aspects. Although the development of feather has been studied for decades, genetic and genomic studies of feather diversity have begun only recently. Many questions remain to be answered by multidisciplinary approaches. In this review, we discuss three levels of feather diversity: Feather morphotypes, intraspecific variations, and interspecific variations. We summarize recent studies of feather evolution in terms of genetics, genomics, and developmental biology and provide perspectives for future research. Specifically, this review includes the following topics: 1) Diversity of feather morphotype; 2) feather diversity among different breeds of domesticated birds, including variations in pigmentation pattern, in feather length or regional identity, in feather orientation, in feather distribution, and in feather structure; and 3) diversity of feathers among avian species, including plumage color and morph differences between species and the regulatory differences in downy feather development between altricial and precocial birds. Finally, we discussed future research directions.

To achieve greater understanding of the full annual cycles of birds, it is critical to describe the spatial nature of little-understood phases. One of the least understood aspects of avian annual cycles is the ecology of molt: the periodic replacement of feathers. While work on the spatial nature of molt in migratory passerines has increasingly found incidences of species and populations completing molt during migration, this work has been limited entirely to prebasic flight feather molt. We examined the prevalence and progression of contour feather molt in a migratory songbird, the Rusty Blackbird (Euphagus carolinus), during spring stopover. We found that 98% of birds exhibited a partial prealternate molt during stopover, primarily in the head region. Furthermore, molt intensity peaked in the middle of the migration period and was negatively associated with fat score. This is the first evidence in the passerine literature of an obligate prealternate molt completed during migration, which is in many ways similar to the molt strategy of a variety of shorebirds (Families Charadriidae and Scolopacidae). These findings could prove crucial to understanding the constraints on spring migration in this declining species. Furthermore, we argue that molt schedules such as those of the Rusty Blackbird and shorebirds should be referred to as “prealternate molt-migration,” broadening the traditional definition of molt-migration beyond prebasic flight feather molt.

Penguins exhibit an array of derived feather features and color-producing mechanisms, including distinct melanosome morphologies and beta-keratin nanofibers that produce blue structural color. Several morphologies have been proposed to have hydrodynamic or insulatory functions. An understanding of the distribution of these morphologies over the body of a single penguin species may elucidate their evolution and function. We investigated feather microstructure and color production mechanisms in blue, black, and white barbs of feathers of the Gentoo Penguin (Pygoscelis papua). Light and scanning electron microscopy revealed that all feathers, regardless of color, are semi-lunate in cross section and lack, or show greatly reduced, air-filled compartments (central vacuoles) in feather barbs. Keratin nanofibers are present in all sampled feathers (including those of 8 other penguin species) but are surrounded by melanin in black barbs and disorganized in white barbs. Reduction of the air-filled central...

Precise locations for the complete feather molt of North American landbirds, relative to their breeding territories, remain undocumented for most species. We analyzed >760,000 records of 140 species at 936 bird-capture stations to assess probabilities of recording both molting landbirds at their breeding sites and breeding birds at molting sites, and to investigate latitudinal, longitudinal, and elevational shifts from breeding to molting grounds. We demonstrate widespread evidence for molt-migrations among a variety of North American landbirds, including many migratory species previously thought to molt on “breeding grounds.” Geospatial differences between breeding and molting grounds were detected in all 4 compass directions as well as both upslope and downslope in elevation, while individuals of some species appeared to disperse to specific molting locations not discriminated by spatial direction or elevation from breeding territories. Although western North American species and populations ar...

Almost all birds use their fight feathers as a means of escaping predators, and their specific design is adapted to their individual circumstances. For example, Galliform birds use a fast, explosive, noisy take-off to startle a predator. Their legs, wings and feathers must work together to create a strong propulsive force and loud, rhythmic sound. Partridges in a group initiate escape simultaneously, even though individuals in the flock differ in size and experience, as well as in age and sex resulting in feathers that differ in length and shape. In a long-term study, we measured 13 814 wild red-legged partridges (Alectoris rufa) to understand how variation in feather proportions and morphometrics between the age-sex classes relate to their escape abilities. We devised two new indexes to quantify the aerodynamic differences between age-sex classes. Our approach synthesizes the understanding of bird take-flight mechanics, feather proportions and the aerodynamic properties of wing tips to show how differences in feather length and tip shape characterize age-sex classes. Our findings suggest that the density, stiffness, permeability, size and shape of the distal primary feathers and wing tips can explain aerodynamic differences between individuals and the efficiency of groups in escape situations., A.M. was supported by a Ramón y Cajal research contract by the Ministry of Economy and Competitiveness (RYC-2012-11867).

The origin of feathers is an important question in Evo-Devo studies, with the eventual evolution of vaned feathers which are aerodynamic, allowing feathered dinosaurs and early birds to fly and venture into new ecological niches. Studying how feathers and scales are developmentally specified provides insight into how a new organ may evolve. We identified feather-associated genes using genomic analyses. The candidate genes were tested by expressing them in chicken and alligator scale forming regions. Ectopic expression of these genes induced intermediate morphotypes between scales and feathers which revealed several major morphogenetic events along this path: Localized growth zone formation, follicle invagination, epithelial branching, feather keratin differentiation, and dermal papilla formation. In addition to molecules known to induce feathers on scales (retinoic acid, β-catenin), we identified novel scale-feather converters (Sox2, Zic1, Grem1, Spry2, Sox18) which induce one or more regulatory modules guiding these morphogenetic events. Some morphotypes resemble filamentous appendages found in feathered dinosaur fossils, whereas others exhibit characteristics of modern avian feathers. We propose these morpho-regulatory modules were used to diversify archosaur scales and to initiate feather evolution. The regulatory combination and hierarchical integration may have led to the formation of extant feather forms. Our study highlights the importance of integrating discoveries between developmental biology and paleontology.

In birds, the preen gland produces a waxy secretion that protects the plumage from environmental conditions and ectoparasites and is, therefore, important for feather maintenance, individual quality, and health. Several studies have demonstrated that the size of the preen gland and the composition of its secretion change throughout the course of reproduction, thus indicating an increased requirement for preen gland secretion during the breeding season. However, the exact timing of the gland's size increase is unknown. To get information about this temporal pattern, we repeatedly measured the preen glands in 22 breeding pairs of adult domesticated Zebra Finches (Taeniopygia guttata) during the course of reproduction (prior to the breeding season, on the day the first egg was laid, on the day the first chick hatched, on the day the first chick fledged, and after the chicks became independent). Zebra Finches have biparental care, in which both sexes are involved in incubation and food provisioning. ...

The expression of elaborated displays provides reliable information to conspecifics about the quality of the signaler. Competition for breeding resources or mates is predicted to affect the expression of signals in both males and females; however, the literature has been typically focused on male behaviors. The spotless starling is an interesting example where both sexes decorate the nest to signal their condition and social status: males add green plants at the beginning of the breeding period, and females place foreign feathers during the incubation period. In this study, we investigate nest decoration by males and females in relation to the intensity of conspecific competition during the breeding period. We distributed nest boxes at either a high (HD) or a low density (LD) and recorded the amount of green plant material added before laying, the number of feathers at hatching, and the breeding productivity under these different density treatments. The amount of green plant material and the number of feathers at hatching were higher in HD than in LD nests. Furthermore, nest boxes at higher density had lower breeding productivity. Our results suggest that manipulating the density of nest boxes increased competition for breeding resources. The aggregation of males competing for territories and mates may stimulate them to add greater amounts of plants, and competition over those males or other resources for reproduction may induce females to add feathers. This study shows that social environment has the potential to influence the expression of signaling behaviors in both males and females., This work was supported the Spanish Ministry of Economy and Competitiveness (project number CGL2014-59670-P). J.G.R. and D.F. were both supported by PhD grants by the Spanish Government.

Effective conservation of migratory bird populations depends on advancements in our understanding of processes throughout the life cycle. Fundamental information about wintering ecology (e.g., habitat use and diet composition) remains limited, which limits assessment of threats to populations during winter. Bobolink (Dolichonyx oryzivorus) is a year-round grassland obligate and Nearctic-Neotropical migrant that undergoes 2 complete molts each year, including a complete prealternate molt on the South American wintering grounds. This unusual winter molt provides a rare opportunity to examine, using stable isotope analysis, the timing and contribution of foraging resources in the Bobolink diet prior to northbound migration from disparate breeding populations. We compared winter diet composition among 3 breeding populations of Bobolinks and during 3 stages of winter molt using stable carbon isotope ratios. We used mixing models to compare the ratio of carbon-12 to carbon-13 isotope (δ13C value) in fe...

SYNOPSIS Flight is the defining characteristic of birds, yet the mechanisms through which flight ability develops are only beginning to be understood. Wing-assisted incline running (WAIR) and controlled flapping descent (CFD) are behaviors that may offer significant adaptive benefits to developing birds. Recent research into these forms of locomotion has focused on species with precocial development, with a particularly rich data set from chukar partridge (Alectoris chukar). Here we briefly review the kinematics and aerodynamics of flight development in this species. We then present novel measurements of the development of pectoralis contractile behavior during the ontogenetic transition toward powered flight. To obtain these new empirical data, we used indwelling electromyography (EMG) and sonomicrometry and tested WAIR and CFD in seven age classes of chukar (n = 2-4 birds per age) from 5 days post hatching (dph) to adult (300+ dph). For each age class, we measured muscle activity during maximal performance, which was WAIR at 65° in birds 5 dph, CFD in birds 9 dph, WAIR at 80° in birds 14 dph, level flight in birds 25-61 dph, and ascending flight in adults. We also measured muscle activity during sub-maximal performance in all age classes. Flapping chukar chicks use near-continuous activation of their pectoralis at relatively low electromyography amplitudes for the first 8 days and progress to stereotypic higher-amplitude activation bursts by Day 12. The pectoralis undergoes increasing strain at higher strain rates with age, and length trajectory becomes more asymmetrical with greater variation in contractile velocity within the shortening phase of individual contractions. At 20-25 days (12-15% adult chukar mass), pectoralis activity and locomotor performance approaches that of adults, although strain rate exhibits a temporary decrease at 61 dph concurrent with using newly-replaced primary feathers. To better understand how these patterns relate to the evolution of life-history strategy and locomotion, we encourage future efforts to explore these behaviors in altricial and semi-altricial bird species.

Understanding the catchment areas of key stopover sites for migratory birds is important for their management and conservation. The Saskatchewan River Delta (SRD) in central Canada is North America's largest inland delta and an important spring and fall stopover site for migratory waterfowl, but there is little information on the origins of waterfowl that use the SRD. We used stable isotope analyses of hydrogen (δ2H) and sulfur (δ34S) in feathers of hunter-killed waterfowl on the SRD to infer natal or molt origins of 5 duck species, using spatially explicit assignment to a δ2H feather isoscape developed for waterfowl in North America. Initial classification with δ2H estimated that 50% were migrants from the north and 10% were assigned to regions south of the SRD, leaving only 39% of the sample with origins in the SRD. Using thresholds in feather δ34S values associated with prairie and forest biomes, we further reassigned 64% of SRD birds as having originated from nearby agricultural and forested ...

Many animals use coloration to signal dominance and fighting ability. In birds, plumage coloration is often linked to individual quality, but less research has investigated coloration in unfeathered traits (i.e. ‘bare parts'), despite theoretical expectations that they might be more reliable signals. Here, we investigate the relationship between multiple ornaments and social dominance in a wild population of the cooperatively breeding Australian Swamphen (known locally as and hereafter referred to as Pūkeko; Porphyrio melanotus melanotus) to test the hypothesis that bare-part ornaments should be more strongly correlated with dominance than plumage coloration. We show that the size and color of the pūkeko's frontal shield (a bare-part ornament), as well as the brightness and chroma of the blue-UV breast plumage, are correlated with social dominance in adult birds. However, the correlation between frontal shield size and dominance was much higher than that between plumage color and dominance, and w...

Feathers serve numerous functions, from flight to interspecific and intraspecific communication. Melanin has been shown to protect feathers from microbial degradation that might, for example, hinder flight or mate attraction. Most studies have focused on the physical resistance to degradation that melanin provides. However, it has yet to be addressed whether melanin alters bacterial colonization and attachment patterns before degradation. We used the common keratinolytic bacterium Bacillus licheniformis to test for preferential attachment and colonization on feathers with black (melanized) and white (unmelanized) stripes. Using experimental inoculation of Eurasian Three-toed Woodpecker (Picoides tridactylus) feathers in vitro and scanning electron microscopy, we show that B. licheniformis preferentially colonizes white feather stripes nearly twice as often as black feather stripes. These data suggest that melanin, in addition to strengthening feathers, may inhibit colonization of keratinolytic ba...

Grooming by birds is thought to serve essential anti-parasite functions. While preening has been well studied, little is known about the function of scratching in birds. We conducted a series of experiments to determine the effectiveness of scratching for controlling feather lice (Columbicola columbae) on Rock Pigeons (Columba livia). First, we used a hobbling technique to impair scratching. After 6 mo, hobbled birds had significantly more lice than controls that could scratch. In addition, lice on hobbled birds were concentrated on the birds’ heads and necks (i.e. the regions that birds scratch). Secondly, we tested the role the claw plays in scratching by declawing nestlings. Once mature, declawed pigeons had significantly more lice than control birds with claws. Moreover, lice on declawed birds were concentrated on the head and neck. Next, we tested whether the flange found on the middle claw of many bird species enhances scratching. We experimentally manipulated the flange; however, the number and location of lice on birds without flanges was not significantly different than that on control birds with intact flanges. Finally, we tested whether scratching removes parasites directly or indirectly by “flushing” them onto body regions where they can be preened. When we impaired scratching (with hobbles) and preening (with “bits”) we found that scratching no longer reduced the number of lice on birds. Our results indicated that scratching and preening work synergistically; scratching reduces parasite load by flushing lice onto regions of the body where they can be eliminated by preening.

Mercury (Hg) is a toxic heavy metal that, when methylated to form methylmercury (MeHg), bioaccumulates in exposed animals and biomagnifies through food webs. The purpose of this study was to assess Hg concentrations in raptors migrating through the upper midwestern USA. From 2009 to 2012, 966 raptors of 11 species were captured at Hawk Ridge, Duluth, Minnesota, USA. Breast feathers were sampled to determine the concentration of total Hg. Mean Hg concentrations ranged from 0.11 to 3.46 μg g−1 fresh weight across species and were generally higher in raptors that feed on birds in comparison with those that feed on mammals. To evaluate the effect of dietary sources on Hg biomagnification, carbon and nitrogen stable isotope ratios were measured in feathers of the 2 species with the highest Hg concentrations, Merlin (Falco columbarius) and Sharp-shinned Hawk (Accipiter striatus). Measured δ 13C values were similar in both species and indicated a primarily terrestrial-derived diet, whereas δ 15N values suggested that individual Merlin and Sharp-shinned Hawk feeding at higher trophic levels accumulated higher concentrations of Hg. The risk to birds associated with measured levels of feather Hg was evaluated by calculating blood-equivalent values using an established algorithm. Predicted blood values were then compared to heuristic risk categories synthesized across avian orders. This analysis suggested that while some Merlin and Sharp-shinned Hawk were at moderate risk to adverse effects of MeHg, most of the sampled birds were at negligible or low risk.

In all animals, susceptibility to parasites can differ among individuals. Young, nest-bound birds are exposed to a diversity of nest-dwelling ectoparasites that typically feed on their blood. Within broods, hatching asynchrony creates size hierarchies that result in morphological and physiological variation among nest mates, and susceptibility to parasites also may vary predictably with this size hierarchy. Our objective was to use a broad-spectrum, anti-parasite drug, ivermectin (IVM), to treat individual nestling Tree Swallows (Tachycineta bicolor) and assess how nestling susceptibility to parasites varied both within and among broods. Broods were either assigned to an IVM group, where half of the nestlings in a brood received IVM injections and half received control injections of pure sesame oil, or to a control group, where all nestlings received oil injections. We found that the IVM treatment reduced parasite loads for broods as a whole, thereby benefiting all nestlings in IVM broods and suggesting our treatment resulted in herd immunity. Specifically, nestlings from IVM broods had higher hemoglobin concentrations, regardless of whether they received injections with IVM or oil, and greater fledging success, than nestlings from control broods. On the contrary, IVM treatment did not strongly affect nestling morphology, with only marginal effects on the growth rate of ninth primary feathers, and the effects of the treatment on 2 other morphological traits depending on temporal factors. Variation in size within broods, however, influenced the chance of an individual fledging, which increased with relative size within a brood, but only under lower parasite loads (i.e. IVM broods). By experimentally manipulating nestling susceptibility to parasites, we have demonstrated variation in nestling response to an anti-parasite treatment both within and among broods, and future studies should investigate the underlying mechanism for why certain nestlings along the brood size hierarchy are more susceptible to parasites.

Feather corticosterone is a popular conservation physiology technique to assess stress in wild populations. We show that it does not correlate with habitat (human disturbance, urbanization, predation, density) or individual (body condition) level stressors in the Hawaiian gallinule, an endangered waterbird that experiences a robust ‘stressor gradient’ across its range., Physiological metrics are becoming popular tools for assessing individual condition and population health to inform wildlife management and conservation decisions. Corticosterone assays can provide information on how animals cope with individual and habitat-level stressors, and the recent development of feather assays is an exciting innovation that could yield important insights for conservation of wild birds. Due to the widespread enthusiasm for feather corticosterone as a potential bioindicator, studies are needed to assess the ability of this technique to detect meaningful differences in physiological stress across a variety of stressor types and intensities. We examined feather corticosterone from 144 individuals among the 13 known breeding populations of Hawaiian gallinule (Gallinula galeata sandvicensis), an endangered waterbird, on the island of O‘ahu. These ecologically independent subpopulations are known to have low genetic connectivity and movement rates and differ largely across a number of important conditions, including level of predator management, human disturbance, proximity to urban development and conspecific population density. This system is well suited for assessing the performance of feather corticosterone as a bioindicator of different known habitat-level threats common to this and many other conservation-reliant species. We found no statistically significant relationship between feather corticosterone and level of predator control, level of human disturbance, gallinule population density, percent urban cover or body condition across all sites despite the substantial difference in stressor magnitude in our dataset. We did find that gallinules in habitats with larger population densities were in worse body condition. These findings suggest that feather corticosterone is not a consistent indicator of anthropogenic impacts on populations. Furthermore, they suggest that feather corticosterone may be a poor bioindicator of known habitat-level threats for Hawaiian gallinules and that it should be used with caution in other avian taxa of conservation concern.

Hippoboscidae (Samouelle 1819) is a family of blood feeding Diptera, which can be phoretic vectors for parasitic feather lice (Philopteridae Burmeister 1838). Hippoboscid flies are understood to provide opportunities for increased instances of dispersal and host-switching for feather lice. This intimate relationship between hippoboscid fly and feather louse may have hypothetically existed since the origin of avian-specialized Hippoboscidae. Thus, phoretic dispersal may have affected patterns of diversification in feather lice over millions of years. To test this, a dating analysis of a previously published Hippoboscoidea data set was performed using known fossil calibrations. The results of the dating analysis suggest Hippoboscoidea diversified shortly after the K-Pg boundary, similar to their modern vertebrate hosts. A maximum age of the avian feeding Ornithomyini is estimated to have occurred around the origin of parasitic feather lice. This maximum divergence date suggest this phoretic relationship could have existed for much of the diversification of avian feather lice and had the potential to influence patterns of diversification due to dispersal and host-switching among avian hosts.

Plumage ornamentation is often considered a signal of fitness, condition, sex, or social status. This theory holds for species with structural UV color, which is influenced by a variety of factors such as environmental pressures during molt or heritability. However, little is known about the consistency of ornamentation and signaling across time in individuals with structural color. We compared juvenile and adult feathers in free-living Florida Scrub-Jays (Aphelocoma coerulescens) to measure UV color change within individuals across molts and to assess possible sources of change. We used multiple imputation to estimate missing data and a combination of pooled estimates and model averaging to infer which parameters explain observed variation in UV color. We also tested whether adult color or relative color change from juvenile to adult plumage predicted acquisition of breeding space. UV color was not consistent across annual molts, as adult feathers reflected significantly less light but greater proportions of UV light than juvenile feathers. Juvenile color was most affected by quality of natal environment and maternal effects whereas adult color was influenced by condition and juvenile color. Adults dosed with corticosterone produced feathers with less UV ornamentation compared to control adults. Feather color did not predict acquisition of breeding space in adults, but females that experienced reductions in UV color across molts were more likely to obtain breeding space, which may reflect sex-specific differences in reproductive strategies in Florida Scrub-Jays. Our evidence suggests that structural color acts as a signal of sex, age, and condition; but ornamentation is only weakly related to acquisition of breeding space and thus unlikely to be under strong sexual selection. Ornamentation may just be one factor among many, such as personality, social dominance, or position in social networks, that determine how jays interact and compete for breeding space.

We report on an exceptional specimen of Eoconfuciusornis preserving rare soft-tissue traces of the ovary and wing. Ovarian follicles preserve a greater hierarchy than observed in Jeholornis and enantiornithines, suggesting confuciusornithiforms evolved higher rates of yolk deposition in parallel with the neornithine lineage. The preserved soft tissues of the wing indicate the presence of a propatagium and postpatagium, whereas an alular patagium is absent. Preserved remnants of the internal support network of the propatagium bear remarkable similarity to that of living birds. Soft tissue suggests the confuciusornithiform propatagium could maintain a cambered profile and generate lift. The feathers of the wing preserve remnants of their original patterning; however, this is not strongly reflected by observable differences under scanning electron microscopy (SEM). The tail plumage lacks elongate rectrices, suggesting that the earliest known confuciusornithiforms were sexually dimorphic in their plumage.

In many avian species, a male's colorful feather ornaments are known to signal individual quality and can serve as the basis for mate choice. Fewer studies have assessed whether this is true for females, who also can display plumage ornaments. We investigated whether breast and crown plumage reflectance in female Prothonotary Warblers (Protonotaria citrea) was correlated with annual reproductive success and nestling provisioning rate. We collected 160 feather samples from 112 nesting female warblers across 5 breeding seasons (2010–2014) in eastern Virginia, USA, and measured their reflectance. Because these data were from a population that was part of a long-term study, we knew the exact age and annual reproductive success of most individuals in all study years. We found a significant positive relationship between crown feather carotenoid content and the number of young fledged, after accounting for the effects of nest initiation date and female age, both of which are known to significantly influ...

Yellow-shafted Flickers (Colaptes auratus auratus subspecies group of the Northern Flicker) occasionally have orange to red flight feathers in eastern North America far from the hybrid zone with the Red-shafted Flicker (C. a. cafer subspecies group). Blocks of feathers of anomalous color tend to show bilateral symmetry and may differ from one year to the next in the same bird. It has been suggested that hybridization with cafer must be the source of the red color and that selection for that color could explain the high incidence of red or orange shafts in eastern flickers in some localities. Complex, though largely unproven, physiological mechanisms have been hypothesized to explain the variegated look. We evaluated a simpler, dietary explanation for the variation: that the pigment rhodoxanthin acquired exogenously at the time of feather molt comes to rest alongside the carotenoids normally present in these feathers. An exogenous source of rhodoxanthin exists in the berries of nonnative bush hone...

Vaquero-Alba and colleagues published a study in The Auk: Ornithological Advances comparing objective color measurements of plumage taken in the field directly on a bird's body to those taken in the lab on collected feathers arranged to emulate the appearance of a bird's natural plumage. Although the field measures of plumage color were less repeatable than lab measures, the authors concluded that measurements taken in the field were more representative of a bird's “true color.” Accordingly, they recommend that researchers should bring spectrophotometers into the field to measure color on live birds. We question the assumption that their field measurements represent true color and highlight concerns regarding their experimental design and methodology. Because they did not measure color of live birds in the lab or the color of plucked feathers in the field, they cannot directly test whether the assessment of color in the field on a live bird is superior. Also, rather than assume field measures are...

The study of feather-degrading microorganisms in avian plumage is steadily growing, but it is still a poorly understood field. Feather-degrading microorganisms were first isolated from chicken feathers in 1992, and their presence in wild birds was first described in 1997. The bulk of research in this area has focused on the possible selection pressures generated by these organisms. Yet we still lack detailed knowledge about the pattern of distribution among species of birds, ecological associations of the birds and feather-degrading microbes, and the effects of these bacteria and fungi on live wild birds. We sampled 3,548 birds representing 154 species for a group of 3 closely related bacilli that are well known to degrade feathers. We found these bacilli to be widespread among birds, occurring in the plumage of 39% of sampled individuals. Furthermore, these bacteria occur in most, if not all, avian taxa at similar frequencies, though variation exists. We found that ground-foraging species had a ...