Wing Patches Research Articles

Looks or personality: what drives damselfly male mating success in the wild?

Understanding the connection between personality and fitness is an important topic in both behavioural and evolutionary ecology. Most of our current knowledge stems from lab-studies despite that studies in natural populations for most parts generate more ecologically relevant information on behavioural variation and mating success. Here, we quantified Calopteryx splendens male mating success across two behavioural axes: courtship and boldness-aggression, testing personality and plasticity of behavioural traits in a natural population situated in the central-core of the species distribution. We also measured wing patch area and body size as these traits are important in damselfly sexual selection. The only behavioural trait that positively affected mating success was consistency in courtship effort. Among morphological traits, smaller wing patch size was associated with greater male mating success, while thorax size was a better predictor of male mating success than either personality or plasticity in boldness and activity. Our results demonstrate the importance of behavioural consistency over plasticity in a wild insect population and support prior studies showing the importance of body size for mating success.

Variability of a consistent trait: The size of the white wing patch in European Stonechats (Saxicola rubicola rubicola)

Numerous bird species exhibit striking white patches on their plumages that have been reported as signals of individual quality in the context of sexual selection. Whereas differences in white plumage traits between individuals have been well studied, phenotypic variation and the factors affecting their consistency within the individual have received less attention. Here, we studied the consistency in the size of the white wing patch and its components of variation in a Spanish population of European Stonechats Saxicola rubicola rubicola monitored over 6 years (2007–2012). The wing patch was larger in males than in females for all age‐classes, and first‐year individuals exhibited smaller wing patches than older birds, particularly males. This trait also varied within the plumage‐year at both population and individual level, with slight changes from the moulting period to the breeding season and a sharp decrease afterwards. In addition, patch size varied both between and within individuals across years. The daily mean temperature experienced in the month immediately prior to the moult (i.e. May) had a positive effect on male wing patch size. In females, however, no variable was found to explain wing patch variation satisfactorily. Despite being a dynamic trait throughout the moults, baseline and adjusted repeatabilities indicated a moderately high consistency for white wing patch size in both sexes. Therefore, the white wing patch in Stonechats is a dynamic trait that changes throughout individuals' lives, but is also a consistent trait at the individual level. These results indicate that this depigmented patch could convey information about both the long‐term quality and the current state of individuals, harmonizing the existence of intra‐individual changes in the size of sexual traits with its potential role as a genetic quality indicator.

Male aggressiveness during the female fertile phase in relation to extra-pair paternity, plumage ornaments and female traits

In many bird species, physical aggression between males become more frequent during the female’s fertile period, as female encounters with extra-pair males are more frequent and can entail paternity losses. Male aggressiveness during this stage has been proposed as crucial for ensuring male reproductive success. Thus, plumage ornaments could represent honest signals of individual quality that could reflect the aggressiveness of paired territorial males. Furthermore, male aggressiveness could be related to mate quality or defensive capacity. We quantified extra-pair paternity in the broods and investigated the association of male and female traits with the aggressive behaviour of territorial paired males in a Spanish population of Pied Flycatchers (Ficedula hypoleuca), where territorial intrusions were simulated during the female fertile period by placing a taxidermic male mount close to the nest. We predicted that (1) more aggressive males should better protect their mates from intruding males and thereby reduce their paternity losses, (2) males with larger white patches and higher UV reflectance of wing patches should respond more strongly to intrusions, and (3) that males should be more aggressive when mated with higher quality females. We found evidence that males that responded less intensely to a territorial intrusion suffered a higher paternity loss, which offers strong support to the basic tenet of the theory of territoriality as paternity defence. Moreover, both the level of male aggressiveness and control of the territory increased with male UV reflectance of wing patches. Finally, we found, contrary to our prediction, that males were less aggressive when mated with more ornamented females.

Male plumage signal expression is related to feather corticosterone concentration in the Pied Flycatcher Ficedula hypoleuca

Male signals may express the capacity to sustain environmental challenges. In some migratory birds like the Pied Flycatcher Ficedula hypoleuca, plumage ornaments are molted in the winter quarters shortly before spring migration while most feathers are replaced shortly after the breeding season in the breeding areas. The concentration of corticosterone in feathers (CORTf) may relate to baseline CORT levels at the time of molt which could be expressed through plumage signals. Male Pied Flycatchers present white patches on forehead feathers and tertials which are molted before spring migration and on secondaries and primaries replaced after breeding. They also express a variable degree of melanisation of head and back feathers molted in the wintering areas. All these plumage traits have been previously shown to function in social contests and/or mate attraction. Here we have collected tertials on the two wings and two tail feathers, molted in wintering and breeding areas respectively, of males in a Spanish montane population and analysed CORTf in the laboratory with standard enzyme immunoassays. There is no correlation within individuals between CORTf in the two types of feathers, although levels are similar. The size of the forehead patch is negatively associated with CORTf in tail feathers, mainly in small males, while the blackness of head and back is negatively related to CORTf in tertials, mainly in large males. The size of the wing patch composed of patches on feathers molted both in wintering (tertials) and breeding areas (primaries and secondaries) is not related to CORTf in any type of feather. Different male plumage traits thus may reflect circulating CORT levels during molt processes occurring in the wintering respectively breeding range as expressed by CORTf in different types of feathers.

White plumage color as an honest indicator: feather macrostructure links reflectance with reproductive effort and success

The structural condition of feathers may generally have a decisive role in shaping the color properties of the plumage. However, the information content of structurally mediated color differences is poorly known. This makes it particularly hard to determine the meaning of color variation in pigment-free white plumage patches. The white wing patch of the collared flycatcher (Ficedula albicollis) is an important sexual trait, and changes in its reflectance are partly due to macrostructural condition. We used 2 years of macrostructural, reflectance, and breeding data from both sexes to examine whether wing patch macrostructure lends information content to actual reflectance in terms of reproductive effort and success. Macrostructure strongly predicted actual reflectance in males but only weakly in females. Furthermore, in males, feather vane width was related positively to current year reproductive effort, and negatively to previous year reproductive effort. This indicates that macrostructurally mediated reflectance attributes may inform the receiver not only of actual reproductive capacity but also of individual quality via reproductive costs.Significance statementColoration of animals takes a central place in their communication and in advertising reproductive abilities. Although white plumage is widespread among animals, usually we have little knowledge on how its structure is linked to reproduction. We investigated this link in a wild population of collared flycatchers. We demonstrated that white feather structure was related to coloration and with current year and previous year reproductive capabilities in males. Our results suggest that white feather structure has the potential to connect reproductive costs with coloration.

Resolving disputed subspecies distribution limits, and revealing intraspecific intergradation, in the Common Redstart Phoenicurus phoenicurus using citizen science and museum data

Contact zones with hybridization are documented for several Palearctic bird taxa. However, their extent is still poorly understood in many cases, including the Common Redstart Phoenicurus phoenicurus. Nominate P. p. phoenicurus breeds across most of the species’ range, whereas P. p. samamisicus is restricted to the south-eastern part. Their precise distributions are disputed as is the existence and prevalence of hybridization between them within potential contact zones in the Balkans, Turkey and the Caucasus region. Adult males differ by the presence (samamisicus) or absence (phoenicurus) of a white wing patch; however, there is variation and white is lacking in most second-calendar-year males of both subspecies. Further, male samamisicus is thought to be darker on the mantle. We map the occurrence of pre-defined states in these two characters during the breeding season across the species’ range based upon photos in online citizen science databases, subsequently complemented by an examination of museum specimens to refute or verify the pattern inferred from photos. We demonstrate that the extent of white in the wing varies throughout the range, but nevertheless is geographically structured. Adult breeders with a large white wing patch and black mantle occurred only in Greece, southern Bulgaria, Turkey, Crimea, and the Caucasus to Iran, which should be considered the breeding range of samamisicus. Earlier reports of intermediates and/or phoenicurus breeding there perhaps reflect confusion with second-year male samamisicus. Broad areas in the Balkans and north of the Black Sea were revealed as zones of intraspecific intergradation. Employing citizen science data enabled us to acquire a much larger sample than by using museum material alone. Although photographs from citizen science databases are unlikely to ever completely replace museum specimens, our approach of combining both types of data could prove a model for similar future research.

Wing scale patterns of Hypolimnas bolina (Linnaeus, 1758) (Lepidoptera: Nymphalidae)

Hypolimnas bolina (L), exhibit a stunningly bright and lustrous colour wing patches. The present study is focused on the variety of pigmented scales that cover the wings of H. bolina. A total of 128 different types of scales (white, brown, blue as well as black scales) were investigated, which includes 63 morphologically different types of scales on the dorsal part and 65 scales from ventral side. For the analysis the scales are taken from the black and violet portion of dorsal part and brown and white colored patches in ventral region. Micrometry of scales on the dorsal side showed a length range of about 86.6 to 102.4? and width range of 63 to 78.8?. Dimension analysis of ventral region range from 86.6 to 106.3? in length and width of 66.8 to 86.6?. The shape and distribution of scale depends on their exact location on the wing which are responsible for boggling pattern and brilliant visual appearance.

Sexual dichromatism, size dimorphism, and microscale anatomy of white wing stripe in blue tits.

Achromatic patches are a common element of plumage patterns in many bird species and there is growing body of evidence that in many avian taxa they can play a signaling role in mate choice. Although the blue tit Cyanistes caeruleus is a well-established model species in the studies on coloration, its white wing patch has never been examined in the context of sex-specific trait expression. In this exploratory study, we examined sexual size dimorphism and dichromatism of greater covert’s dots creating white wing patch and analyzed its correlations with current body condition and crown coloration—a trait with established role in sexual selection. Further, we qualitatively analyzed microstructural barb morphology underlying covert’s coloration. We found significant sexual dimorphism in the dot size independent of covert size and sexual dichromatism in both white dot and blue outer covert’s vane spectral characteristics. Internal structure of covert barbs within the white dot was similar to the one found in barbs from the blue part that is, with a medullary area consisting of dead keratinocytes containing channel-type ß-keratin spongy nanostructure and centrally located air cavities. However, it lacked melanosomes which was the main observed difference. Importantly, UV chroma of covert’s blue vane was positively correlated with crown UV chroma and current condition (the latter only in males), which should be a premise for further research on the signal function of the wing stripe.

The extent of white plumage patches in female Pied Flycatchers Ficedula hypoleuca is negatively associated with corticosterone concentration in partly unpigmented feathers

Sexually and socially selected signals are predicated to express the present and past condition of individuals and thereby their capacity to cope with environmental challenges. The concentration of corticosterone in feathers (CORTf) has been validated as a marker of activation of the hypothalamic-pituitary axis in birds during feather development. Measurements of CORTf can thus express the physiological stress of migratory birds during non-breeding periods of the annual cycle when feathers moulted in the wintering range are analysed. Thus, negative trends of ornament expression with CORTf may be predicted. Unpigmented plumage patches may constitute signals of phenotypic quality and are used in many species in social interactions by both sexes. Pied Flycatchers of both sexes Ficedula hypoleuca show white forehead and wing patches during the breeding season, of which the forehead and part of the wing patch (tertials) are moulted on the wintering grounds before spring migration. These patches are used as signals in social and sexual interactions and their expression has been previously related to several indicators of physiological status. We collected tertials of females during nestling provisioning in a Spanish population and determined their CORTf in the laboratory. CORTf was thus measured in some of the prenuptially moulted feathers used as signals of social dominance by breeding females. According to AICc model selection, CORTf turned up in all the best models explaining forehead patch size and in most best models for wing patch size when controlling for age and size. Both forehead and wing patch sizes were negatively related to CORTf, although the trend for wing patch size was not significant. This indicates that breeding females expressing large unpigmented patches experienced low levels of stress during the prenuptial moult in their winter quarters, or that strongly signalling individuals present a lower level of activation of the HPA axis.

Preference for supernormal stimuli tends to override initially learned associations for conspicuous prey traits: implications from a laboratory study

How predators select on conspicuous prey traits is not well understood. We used a laboratory setup to investigate the role of learning in predator choice of conspicuous visual traits. We used a generalist predator, the great tit, and coloured wings of males of two species of damselflies as prey. Wing pigmentation differs between the species in colour (green vs. blue) and size (large vs. small). Wing pigmentation is a sexually selected trait that experiences negative selection by avian predators. Inexperienced great tits showed no preference for the colour or the size of wing pigmentation. Great tits were then repeatedly exposed to rewarded wings with either large or small wing patch size. When these experienced birds were exposed to both wing patch sizes for the first time, they tended to prefer the wings with the large patch, irrespective of their previous experience. Our results suggest that the choice of the predator was based on an initial association of the trait to a reward followed by a preference for a supernormal stimulus, probably due to a larger sensory stimulation. We discuss the implications of our laboratory results in the light of previous estimates of damselfly predation risk under field conditions.

Macroevolutionary bursts and constraints generate a rainbow in a clade of tropical birds

BackgroundBird plumage exhibits a diversity of colors that serve functional roles ranging from signaling to camouflage and thermoregulation. However, birds must maintain a balance between evolving colorful signals to attract mates, minimizing conspicuousness to predators, and optimizing adaptation to climate conditions. Examining plumage color macroevolution provides a framework for understanding this dynamic interplay over phylogenetic scales. Plumage evolution due to a single overarching process, such as selection, may generate the same macroevolutionary pattern of color variation across all body regions. In contrast, independent processes may partition plumage and produce region-specific patterns. To test these alternative scenarios, we collected color data from museum specimens of an ornate clade of birds, the Australasian lorikeets, using visible-light and UV-light photography, and comparative methods. We predicted that the diversification of homologous feather regions, i.e., patches, known to be involved in sexual signaling (e.g., face) would be less constrained than patches on the back and wings, where new color states may come at the cost of crypsis. Because environmental adaptation may drive evolution towards or away from color states, we tested whether climate more strongly covaried with plumage regions under greater or weaker macroevolutionary constraint.ResultsWe found that alternative macroevolutionary models and varying rates best describe color evolution, a pattern consistent with our prediction that different plumage regions evolved in response to independent processes. Modeling plumage regions independently, in functional groups, and all together showed that patches with similar macroevolutionary models clustered together into distinct regions (e.g., head, wing, belly), which suggests that plumage does not evolve as a single trait in this group. Wing patches, which were conserved on a macroevolutionary scale, covaried with climate more strongly than plumage regions (e.g., head), which diversified in a burst.ConclusionsOverall, our results support the hypothesis that the extraordinary color diversity in the lorikeets was generated by a mosaic of evolutionary processes acting on plumage region subsets. Partitioning of plumage regions in different parts of the body provides a mechanism that allows birds to evolve bright colors for signaling and remain hidden from predators or adapt to local climatic conditions.

An experimental increase in female mass during the fertile phase leads to higher levels of extra-pair paternity in pied flycatchers Ficedula hypoleuca

Female mass in most altricial birds reaches its maximum during breeding at egg laying, which coincides temporally with the fertile phase when extra-pair paternity (EPP) is determined. Higher mass at laying may have two different effects on EPP intensity. On the one hand, it would lead to increased wing loading (body mass/wing area), which may impair flight efficiency and thereby reduce female’s capacity to resist unwanted extra-pair male approaches (sexual conflict hypothesis). On the other hand, it would enhance female condition, favouring her capacity to evade mate guarding and to search for extra-pair mates (female choice hypothesis). In both cases, higher female mass at laying may lead to enhanced EPP. To test this prediction, we reduced nest building effort by adding a completely constructed nest in an experimental group of female pied flycatchers (Ficedula hypoleuca). Our treatment caused an increase in mass and thereby wing loading and this was translated into a significantly higher EPP in the manipulated group compared with the control group as expected. There was also a significant negative relationship between EPP and laying date and the extent of the white wing patch, an index of female dominance. More body reserves at laying mean not only a higher potential fecundity but a higher level of EPP as well. This interaction had not previously received due attention but should be considered in future studies of avian breeding strategies. While most research has been focused on determining possible criteria for extra-pair mate choice by females, less effort has been made on establishing if female traits are related to EPP and its intensity. One such trait is mass at laying which attains its highest level for breeding females of altricial birds. Our study indicates that a higher mass during the fertile phase not only has implications for female fecundity and predation risk but also for EPP in the resulting brood as more mass means a higher EPP.

A Dynamic Optical Signal in a Nocturnal Moth.

The wings of butterflies and moths generate some of the most spectacular visual displays observed in nature [1-3]. Particularly striking effects are seen when light interferes with nanostructure materials in the wing scales, generating bright, directional colors that often serve as dynamic visual signals [4]. Structural coloration is not known in night-flying Lepidoptera, yet here we show a highly unusual form of wing coloration in a nocturnal, sexually dimorphic moth, Eudocima materna (Noctuidae). Males feature three dark wing patches on the dorsal forewings, and the apparent size of these patches strongly varies depending on the angle of the wing to the viewer. These optical special effects are generated using specialized wing scales that are tilted on the wing and behave like mirrors. At near-normal incidence of light, these "mirror scales" act as thin-film reflectors to produce a sparkly effect, but when light is incident at ∼20°-30° from normal, the reflectance spectrum is dominated by the diffuse scattering of the underlying, black melanin-containing scales, causing a shape-shifting effect. The strong sexual dimorphism in the arrangement and architecture of the scale nanostructures suggests that these patterns might function for sexual signaling. Flickering of the male's wings would yield a flashing, supernormal visual stimulus [5] to a viewer located 20°-30° away from the vertical, while being invisible to a viewer directly above the animal. Our findings reveal a novel use of structural coloration in nature that yields a dynamic, time-dependent achromatic optical signal that may be optimized for visual signaling in dim light.

Ornaments and condition: plumage patch sizes, nutritional reserve state, reserve accumulation, and reserve depletion

Condition-dependence is considered as a dominant mechanism ensuring the fitness benefits of continued mate choice for heritable sexual signal traits, but crucial questions remain concerning the underlying physiological pathways. For example, it is unclear whether condition-dependence is mediated by the different amount of resource obtained, some uncheatable functional link with nutritional status, or the adverse effect of nutritional stress experienced by some individuals. Furthermore, the pattern of change in nutritional reserves in relation to ornamental traits has recently been proposed as a critical pillar of the condition-dependence concept, but this pattern is virtually unknown in natural populations. We quantified separate measures for actual body condition, lipid reserve accumulation rate, and lipid reserve depletion, and applied these measures to two white plumage ornaments of male collared flycatchers during courtship, during nestling rearing, and before the summer moult. Neither actual condition nor reserve accumulation rate before moult predicted the subsequent change of ornament sizes, but reserve depletion was accompanied by the reduction of forehead patch size to the following year. Wing patch size, a trait important in territoriality, was negatively related to both reserve accumulation and reserve depletion in the courtship period, but not related to current condition. Finally, irrespective of breeding phase, measures of current condition, and recent nutritional reserve depletion were negatively correlated, but both were unrelated to resource accumulation rate. These results indicate that measuring nutritional reserve trajectories in addition to actual condition may reveal functionally important processes underlying signal-condition correlations.Significance statementOrnamental signal characters are known to convey honest information to signal receivers through their dependence on nutritional condition. Here, we show that such signals can also indicate the temporal trends of condition. We examine plumage patch sizes and separate measures of actual condition, nutritional reserve accumulation, and nutritional reserve depletion in three contexts: during courtship, during nestling rearing, and before the summer moult. The results suggest nutritional stress effects on signal expression, and predictable reserve dynamics in relation to signal expression, thereby highlighting the usefulness of dynamic nutritional measures in clarifying the fundamental concept of condition-dependent signalling.

Wing-Flashing by Northern Mockingbirds While Foraging and in Response to a Predator Model

Some insectivorous avian species may improve foraging success by flashing conspicuously colored wing patches or tail spots to startle potential prey and elicit escape behavior. While some studies of Mimus polyglottos (Northern Mockingbird) suggest that wing-flashing (WF) behavior may enhance strike rate and/or foraging success, other studies are equivocal or suggest a negative relationship. Anecdotal observations suggest that WF in mockingbirds may serve an additional role, as this behavior has been documented in response to a potential predator. The biological roles of WF remain unclear in Northern Mockingbirds; thus, we sought to systematically study: (1) the seasonal use of WF while foraging, and (2) the behavioral response of mockingbirds when presented with 2 model organisms—a nest predator and a neutral avian species. We found that foraging bouts during the reproductive period were more likely to include WF than those during the non-reproductive period, but that there was no significant relationship between WF rate and either strike rate or foraging-success rate. When exposed to models, mockingbirds only employed WF during the reproductive period, and then, only to the predator model. Our results suggest that WF is confined primarily to the reproductive period of the annual cycle, and that this behavior is utilized while foraging and in response to the presence of a potential predator. However, the biological role WF plays in both of these circumstances bears further examination.

Phenotypic plasticity in breeding plumage signals in both sexes of a migratory bird: responses to breeding conditions

Adaptive phenotypic plasticity may respond to present ambient conditions. Sexual and social signals in both sexes may express phenotype performance. Plumage signals that change discontinuously allow relating discrete variation to previous performance. Both sexes of the pied flycatcher Ficedula hypoleuca present white patches on the wings and on the forehead, which constitute sexual and social signals. Forehead patches are moulted together with body plumage in Africa, while wing patches are partly moulted in Africa and partly in the breeding area soon after breeding. We studied individual inter‐year changes (corrected for regression to the mean) in the size of forehead and wing patches of both sexes in seven years for females or six years for males in two nearby study areas in central Spain. We found that initial signal extent strongly delimits the possible subsequent changes negatively. There is a negative association of male age with forehead patch changes. Cold and rainy springs are associated in females with decreases in both patch areas and vice versa, while no association with climate is observed in male wing patch changes. Cold pre‐breeding conditions predict positive changes in female wing and male forehead patches. Breeding success is positively associated with forehead patch changes in females. Late‐breeding males experience more positive changes in forehead patch size than early‐breeding males. Some of these trends can be explained by variable costs of breeding in certain conditions for subsequent signal production and/or maintenance, while absence of trends in some cases may be explained by sex differences in costs of breeding and interactions with phenotypic quality of breeders.

Uropygial gland size: a marker of phenotypic quality that shows no senescence in a long-lived seabird.

Studies of senescence in the wild have traditionally focused on traits like survival or fecundity. Although efforts to measure other salient phenotypic traits and markers of relevant physiological processes are rapidly increasing, traits related to self-maintenance remain understudied in the context of aging. Uropygial or preen gland is a holocrine gland, exclusive to birds, directly linked to self-maintenance of the quality of plumage. We measured the size of uropygial glands of common gulls (Larus canus) in a cross sectional manner in order to test whether it shows the similar age-related decline as reproductive traits previously recorded in this species. Gulls with larger glands started breeding earlier in the season, indicating that gland size is a marker of individual phenotypic quality. We found a senescent decline in the onset of breeding and the size of white wing patches, a sexually dimorphic ornamental trait, while in contrast, preen gland increased with advancing age. This finding supports the view of life-history theory that in long-lived species whose lifetime reproductive success depends heavily on lifespan, self-maintenance is prioritized over reproduction. Altogether our results support the concept that senescence in the wild can be asynchronous for traits related to maintenance versus reproduction.

Ecological crossovers of sexual signaling in a migratory bird.

Environmental shifts may induce sudden reversals in the relative quality or sexual attractiveness of mates (ecological crossovers) leading to non-directional sexual selection. Studies on such ecological crossovers induced by environmental shifts during the nonbreeding season are particularly rare. We studied the interactive effects between nonbreeding conditions and a male white wing patch on the breeding success of breeding pairs and the local survival of females in a migratory passerine population over a 32-year period. After dry winters, females paired with large-patched males were more likely to survive than those paired with small-patched males, and vice versa after moist winters. Moreover, after dry winters, large-patched males succeeded in attracting females that laid large clutches, while small-patched males bred with females that laid small clutches, and vice versa after moist winters. This phenomenon led to a difference in fledgling numbers only during years with dry winters and high precipitation during the breeding season. The selection on this male trait and its signaling value to females thus depended on a complex interaction between conditions both at the nonbreeding and breeding grounds. We show that it is important to consider conditions during the nonbreeding season when examining the effects of sexual ornaments on fitness.

Female incubation attendance and nest vigilance reflect social signaling capacity: a field experiment

Due to the reduced conspicuousness of female signals, their evolution has traditionally been interpreted as a by-product of sexual or natural selection in males. Recent studies have argued that they may be the result of sexual or social selection acting on females. Here, we explored the role of the white wing patch during the incubation period in female-female competition contests in a migratory cavity-nesting songbird, the pied flycatcher Ficedula hypoleuca. At this stage, female investment is crucial for offspring survival, while competition among females for nest cavities is still operating. We experimentally performed an extreme reduction of signaling capacity by covering the wing patch with dark paint in a group of females and compared their incubation attendance and social interaction patterns (vigilance and aggression at the nest as defense variables) during simulated territorial intrusion tests with female decoys, with those of an unmanipulated group of females. Tests were performed both before and after the manipulation. We hypothesized that these patches constitute signals of social dominance in female-female interactions that allow them to maintain high levels of incubation attendance by reducing the need for vigilance. We found a marked decrease in incubation attendance in experimental females after manipulation, a change that was not found in the control group. Moreover, vigilance decreased in the control group after the manipulation, a change not detected in manipulated females. No effects on aggressive nest defense were found. Female wing ornamental traits would act as a badge of status in social interactions allowing more intense incubation and reduced vigilance. Implications of social interactions on incubation patterns should be incorporated in future studies. Animals can transmit information to the others through different traits. Ornamental signals have been proposed as status indicators in social interactions in birds in many studies. Although some of them concern their function and evolution in females, only a few have been focused on their role during incubation. Our experimental study suggests that the female’s white wing patch in pied flycatchers acts as a badge of dominance status in social encounters. Thus, dominant females may enforce respect from competitors through signaling, thereby being able to reduce vigilance at the nest with positive effects on incubation efficiency. Implications of social status for incubation patterns should be considered in future studies as an additional factor modulating this crucial parental activity.

Longwing (Heliconius) butterflies combine a restricted set of pigmentary and structural coloration mechanisms

BackgroundLongwing butterflies, Heliconius sp., also called heliconians, are striking examples of diversity and mimicry in butterflies. Heliconians feature strongly colored patterns on their wings, arising from wing scales colored by pigments and/or nanostructures, which serve as an aposematic signal.ResultsHere, we investigate the coloration mechanisms among several species of Heliconius by applying scanning electron microscopy, (micro)spectrophotometry, and imaging scatterometry. We identify seven kinds of colored scales within Heliconius whose coloration is derived from pigments, nanostructures or both. In yellow-, orange- and red-colored wing patches, both cover and ground scales contain wavelength-selective absorbing pigments, 3-OH-kynurenine, xanthommatin and/or dihydroxanthommatin. In blue wing patches, the cover scales are blue either due to interference of light in the thin-film lower lamina (e.g., H. doris) or in the multilayered lamellae in the scale ridges (so-called ridge reflectors, e.g., H. sara and H. erato); the underlying ground scales are black. In the white wing patches, both cover and ground scales are blue due to their thin-film lower lamina, but because they are stacked upon each other and at the wing substrate, a faint bluish to white color results. Lastly, green wing patches (H. doris) have cover scales with blue-reflecting thin films and short-wavelength absorbing 3-OH-kynurenine, together causing a green color.ConclusionsThe pigmentary and structural traits are discussed in relation to their phylogenetic distribution and the evolution of vision in this highly interesting clade of butterflies.