Tail Ornaments Research Articles

Redescription and phylogenetic affinities of the Early Cretaceous enantiornithine Dapingfangornis sentisorhinus.

Dapingfangornis sentisorhinus, a small to medium-sized enantiornithine from the Lower Cretaceous Jiufotang Formation in Western Liaoning, China, stands as one of the earliest known enantiornithines with well-preserved ornamental tail feathers. However, the original holotype description was limited due to damage and matrix interference, which obscured crucial osteological details. Therefore, we provide an updated description of the holotype specimen of D. sentisorhinus with the aid of CT scanning to reveal new and revised osteological information. Furthermore, a phylogenetic analysis of newly acquired data situates Dapingfangornis within the Enantiornithes, closely aligned with Pterygornis and a few other taxa, which may represent a previously unrecognized clade of Early Cretaceous enantiornithines.

Extrapair mating opportunity explains the evolutionary transition between the presence and absence of tail ornamentation in swallows

Extrapair mating opportunity explains the evolutionary transition between the presence and absence of tail ornamentation in swallows

Subtle, pervasive genetic correlation between the sexes in the evolution of dimorphic hummingbird tail ornaments.

Male hummingbirds have repeatedly evolved sexually dimorphic tails that they use as ornaments during courtship. We examine how male ornament evolution is reflected in female morphology. Lande's two-step model of the evolution of dimorphism predicts that γ (the genetic correlation between the sexes) causes trait elaboration to first evolve quickly in both sexes, then dimorphism evolves more slowly. On the hummingbird phylogeny, tail length does not fit this two-step model; although hummingbirds repeatedly evolved ornamental, elongated tails, dimorphism evolves on the same phylogenetic branch as elongation, implying that γ quickly evolves to be low over phylogenetic timescales. Male "bee" hummingbirds have evolved diverse rectrix shapes that they use to produce sound. Female morphologies exhibit subtle, pervasive correlations with male morphology. No female-adaptive hypotheses explain these correlations, since females do not also make sounds with their tail. Subtle shape similarity has arisen through the genetic correlation with males, and is subject to intralocus sexual conflict. Intralocus sexual conflict may produce increased phenotypic variation of female ornaments. Other evolutionary constraints on tail morphology include a developmental correlation between neighboring tail-feathers, biasing tail elaboration to occur most often at the ends of the feather tract (rectrix 5 or 1) and not the middle.

Sexually dimorphic swallows have higher extinction risk.

The effect of sexual selection on extinction risk remains unclear. In theory, sexual selection can lead to both increase and decrease extinction probability depending on the ecology of the study system. Thus, combining different groups might obscure patterns that can be found in groups that share similar ecological features. Using phylogenetic comparative analysis, we studied sexual plumage dimorphism in relation to the perceived risk of extinction in hirundines (subfamily: Hirundininae), in which all species are socially monogamous aerial foragers. Among the 72 species studied, five species are facing a perceived threat of extinction. Species with sexually dimorphic plumage had a higher risk of extinction than did species with sexually monomorphic plumage. Likewise, when focusing solely on tail ornamentation, species that exhibit a sexual dimorphism in tail length had a higher risk of extinction than did other species. In Hirundininae, which are affected a great deal by severe weather, sexual selection and the resultant sexual dimorphism would increase extinction risk.

Negative interplay of tail and throat ornaments at pair formation in male barn swallows

Pair formation is indispensable for breeding in monogamous species, generating selection for male traits that increase the probability of pairing success. Male ornamentation is one such trait, and several empirical studies have shown the importance of each of multiple ornaments. Still, it remains unclear how multiple ornaments in combination affect the probability of pair formation. Using the Japanese barn swallow, Hirundo rustica gutturalis, we studied the interplay of two sexually selected male traits, tail length and throat coloration, during pair formation. Independent of other morphological, ornamental and abiotic variables, the probability of pair formation was predicted by the negative interplay between tail length and plumage colour saturation: males possessing more-colourful plumage with shorter tails or males possessing less-colourful plumage with longer tails had a higher probability of pair formation than others. The current findings may explain spatiotemporal variation in ornamentation and sexual selection in this model species.

Mate choice plasticity in a coral reef fish

Mate choice and intrasexual mating competition are the processes that drive sexual selection and can be interrelated in multiple ways. Female preference may be altered by exposure to male-male interactions. This could happen because of a reduced ability of females to evaluate males in the presence of male-male competition or because females use information from male interactions to form mating preferences. In this study, female preference for a male tail ornament was measured in the presence and absence of male-male competition in a coral reef fish, the damselfish Chrysiptera cyanea. Despite the striking colors of coral reef fishes, few studies have investigated the role of their coloration in the context of sexual selection. When male-male interactions were prevented, females showed a temporal change in preference with respect to male tail coloration, preferring brightly colored males early in the study period and dull males later on. Thus, females did not become less selective, but reversed their preference function within the breeding season. When males were allowed to interact, male-male agonistic interactions were extremely frequent and male courtship activity was strongly reduced. In this situation, females still displayeda sexual interest in males, but were indiscriminate with regard to male tail coloration.Taken together, these results provide compelling evidence for plasticity of female matingpreference, related to the social context and time in the breeding season.

A new Early Cretaceous enantiornithine (Aves, Ornithothoraces) from northwestern China with elaborate tail ornamentation

ABSTRACTWe provide a detailed description of a well-preserved enantiornithine specimen (GSGM-05-CM-004) from the Lower Cretaceous (Aptian) Xiagou Formation of northwestern Gansu Province, China, for which we erect the new taxon Feitianius paradisi, gen. et sp. nov. This specimen has a distinctive pelvic morphology and can be further distinguished from all other Mesozoic birds by a unique caudal plumage formed by multiple rectricial morphotypes. This newly documented tail morphology reveals a previously unrecognized level of complexity in the plumage of basal birds. This complex tail-feather morphology has a parallel in extant sexually dimorphic birds in which the males have the most altered tails; thus, we identify this specimen as male. Ornamental tail morphologies, such as the novel tail plumage described here, dominate Enantiornithes. This reinforces hypotheses that sexual selection was a major driving force in the evolution of basal bird plumage.http://zoobank.org/urn:lsid:zoobank.org:pub:8BEF4422-58C5-487B-B76A-51C5855CF87BSUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: O’Connor, J. K., D.-Q. Li, M. C. Lamanna, M. Wang, J. D. Harris, J. Atterholt, and H.-L. You. 2015. A new Early Cretaceous enantiornithine (Aves, Ornithothoraces) from northwestern China with elaborate tail ornamentation. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2015.1054035.

Hindlimb feathers in paravians: Primarily “wings” or ornaments?

Recently a specimen of Sapeornis was described with feathers around the ankle joint, the first basal bird with metatarsal feathers. The discovery of several groups of paravians with feathered distal hindlimbs has been used as evidence that flight in Aves evolved through a tetrapteryx stage. However, most specimens of Sapeornis do not preserve feathers around the feet, and these feathers are clearly absent in at least one exceptional specimen preserving skin and feather impressions. This suggests that the presence of ankle feathers in Sapeornis may alternatively be interpreted as ornamentation. Basal birds show more ornamental tail morphologies than aerodynamic ones suggesting that sexual selection played a dominant role in shaping tail plumage. Feathers on the forelimbs initially evolved for a purpose other than flight and we propose aerodynamics was not the driving force in hindlimb feather evolution. We suggest that feathers as a means of visual communication played a very important role in the evolution of paravian plumage.

Melanic coloration differentially predicts transfer of immune factors to eggs with daughters or sons

Maternal allocation shapes offspring phenotype by being tailored to parental phenotype and offspring sex. Because melanogenesis and immunity have partly common genetic control, maternal effects via egg immune factors and parental melanization may covary. Here, we tested whether barn swallows Hirundo rustica allocated antibodies against a novel antigen to their eggs according to embryo sex depending on maternal melanin-based coloration while controlling for paternal tail ornamentation. Egg antibody concentration increased with maternal plumage darkness in broods with relatively more females, whereas it decreased in broods with relatively more males. Thus, darker females allocated more antibodies to their eggs when offspring sex ratio was female biased, whereas paler females allocated more antibodies to the eggs when offspring sex ratio was male biased. These effects were independent of laying order. Our results are compatible with the hypotheses that maternal allocation to sons depends on their reproductive value as predicted by heritable melanin-based coloration and with the hypothesis of differential susceptibility of pheomelanic daughters to parasitism. These effects may depend on pleiotropy of the genes that control melanogenesis and immunity, which may differentially act on investment in self-maintenance and maternal effects. This study is the first study in vertebrates of the association between maternal effects on either sex via egg quality and parental melanization. The links between the genetic control of melanogenesis and of major fitness traits like immunity and the role of maternal effects in reproductive strategies prompt for more studies of the covariation between parental coloration and maternal sex-dependent allocation via egg quality.

Population differences in density and resource allocation of ornamental tail feathers in the barn swallow

Many organisms show well-defined latitudinal clines in morphology, which appear to be caused by spatially varying natural selection, resulting in different optimal phenotypes in each location. Such spatial variability raises an interesting question, with different prospects for the action of sexual selection on characters that have a dual purpose, such as locomotion and sexual attraction. The outermost tail feathers of barn swallows (Hirundo rustica) represent one such character, and their evolution has been a classic model subject to intense debate. In the present study, we examined individuals from four European populations to analyze geographical variation in the length and mass of tail feathers in relation to body size and wing size. Tail feather length differed between sexes and populations, and such variation was a result of the effects of natural selection, acting through differences in body size and wing size, as well as the effects of sexual selection that favours longer tails. The extra enlargement of the tail promoted by sexual selection (i.e. beyond the natural selection optimum) could be achieved by increasing investment in ornaments, and by modifying feather structure to produce longer feathers of lower density. These two separate processes accounting for the production of longer and more costly tail feathers and less dense feathers, respectively, are consistent with the hypothesis that both Zahavian and Fisherian mechanisms may be involved in the evolution of the long tails of male barn swallows. We hypothesize that the strength of sexual selection increases with latitude because of the need for rapid mating as a result of the short duration of the breeding season at high latitudes. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 925–936.

Male barn swallows use different signalling rules to produce ornamental tail feathers

The evolution of secondary sexual characters is the subject of controversial debate between those defending their role as ‘viability indicators’ and those arguing that ornaments are purely ‘attractive traits’ selected by females. Recent theoretical studies suggest that these hypotheses are not mutually exclusive, as both viability and attractiveness can contribute to improve the reproductive success of progeny and could thus simultaneously underlie female choices. If that is the case, strategies of cheaper advertisement, allowing the expression of larger ornaments for the same cost, could proliferate even in species in which honest signalling of viability prevails. Under this scenario, different males could invest a different amount of resources per ornament unit of expression, thus using different signalling rules. We studied the relationship between tail feather length (a trait that is the subject of a female mate preference) and feather mass (a measure of investment in feather production) in a barn swallow Hirundo rustica population. Different males used different and consistent signalling rules when developing ornamental feathers. That is, to produce a feather of a given length, each male used a constant amount of resources across different years, but this amount varied between males. Although the amount of material invested in feathers (feather mass) is a condition-dependent trait, the organization of this material in ornamental feathers (i.e. the signalling rules) was not. Neither survival nor risk of feather breakage was related to the signalling rules. Thus, these results suggest that both ‘viability’ and ‘runaway’ mechanisms are independent determinants of the evolution of ornamental sexual feathers in the barn swallow. A preference for long tails will ensure that females either obtain a sire with high viability, or one transferring the capability to produce longer and more attractive tails at a lower cost of production to its offspring.

Brood overlap and male ornamentation in the double-brooded barn swallow

Brood overlap can be an optimal solution to the intraseasonal trade-off in the allocation of time between successive broods. In line with life-history theory, the extent of brood overlap should be adjusted according to the individual costs and benefits of the simultaneous investment into 2 broods. Phenotypic quality can affect these costs and benefits. In barn swallows (Hirundo rustica), male tail streamer length is a phenotypic quality trait, which is related to reproductive decisions, resulting in pairs with long-tailed males showing higher annual output than those with short-tailed males. We predict that the extent of brood overlap in barn swallows is positively associated with the male’s tail ornamentation. Using radiotelemetry, we assessed the duration of postfledging care and juvenile survival and quantified brood overlap with unprecedented accuracy. Broods of pairs with highly ornamented males overlapped to a larger extent than those of pairs with short-tailed males. Brood overlap depended on the reproductive value of the previous brood and on female phenotypic quality. Clutch initiation after a short interbrood interval was associated with a great brood overlap. Short duration of postfledging care but not brood overlap reduced fledgling survival in first broods, and earlier second broods were associated with enlarged clutches. Thus, pairs with long-tailed males managed to increase clutch size and survival of the second brood by an early onset without incurring survival costs in the first brood. This is in line with the hypothesis that brood overlap enforces differential annual reproductive output among individuals varying in phenotypic quality.

Long tails matter in sugarbirds—positively for extrapair but negatively for within-pair fertilization success

Extrapair mating is known to occur in many animals and potentially has a significant influence on reproductive success. Female extrapair mate choice may explain the occurrence of exaggerated ornaments in socially monogamous species, but the influence of ornamentation on extrapair mating success has rarely been investigated experimentally. Cape sugarbirds (Promerops cafer) are socially monogamous, almost always lay 2 egg clutches and have long-term pair bonds often lasting several seasons. However, they also display sexually dimorphic extravagant ornamentation in the form of a long, graduated tail and have one of the highest rates (65% of young) of extrapair paternity recorded in birds. We provide a test of the hypothesis that the ornamented tail is used in mate choice for extrapair partners by conducting an experiment in which tail length was manipulated after social mating but before copulation. This experiment therefore allowed females to respond to the manipulation of male tail length when making a choice of copulation partner but not social mate. We show that the tail length of male sugarbirds has a significant effect on the success of males in gaining extrapair paternity, with long-tailed males obtaining significantly more extrapair young than shorttailed males. However, males with short tails sire a significantly greater proportion of the nestlings in their own nests than longtailed individuals. This result suggests that males may adopt alternative strategies dependent on their ornamentation. Key words: extrapair mating, mate choice, Pomerops cafer, sexual selection, sugarbird, tail ornamentation. [Behav Ecol]

Phylogeny and evolution of sexually selected tail ornamentation in widowbirds and bishops (Euplectesspp.)

Despite similar ecology, mating systems and female preferences for supernormal tails, the 17 species of African widowbirds and bishops (Euplectes spp.) show astonishing variation in male tail ornamentation. Whereas bishops retain their brown nonbreeding tails in nuptial plumage, widowbirds grow black nuptial tails, varying in length from a few centimetres in E. axillaris to the extreme half metre train of E. progne. Here, we phylogenetically reconstruct the evolution of the discrete trait, nuptial tail and the continuous trait, tail length, using a molecular phylogeny of 33 Euplectes subspecies. Unlike many recent findings of labile evolution of plumage ornaments, our results suggest that the nuptial tail of Euplectes is a derived and phylogenetically conserved ornamental trait that, once gained, shows directional evolution in its expression. Directionality is demonstrated in the trivial sense of a short-tailed ancestor, and by contingency and randomization tests suggesting that branches with increasing tail length are overrepresented. This supports an early origin and strong retention of directional female mate choice in widowbirds and bishops, as previously indicated by empirical and experimental results, and provides a less labile, yet rapid scenario of sexually selected diversification.

The allometric pattern of sexually size dimorphic feather ornaments and factors affecting allometry

The static allometry of secondary sexual characters is currently subject to debate. While some studies suggest an almost universal positive allometry for such traits, but isometry or negative allometry for nonornamental traits, other studies maintain that any kind of allometric pattern is possible. Therefore, we investigated the allometry of sexually size dimorphic feather ornaments in 67 species of birds. We also studied the allometry of female feathers homologous to male ornaments (female ornaments in the following) and ordinary nonsexual traits. Allometries were estimated as reduced major axis slopes of trait length on tarsus length. Ornamental feathers showed positive allometric slopes in both sexes, although that was not a peculiarity for ornamental feathers, because nonsexual tail feathers also showed positive allometry. Migration distance (in males) and relative size of the tail ornament (in females) tended to be negatively related to the allometric slope of tail feather ornaments, although these results were not conclusive. Finally, we found an association between mating system and allometry of tail feather ornaments, with species with more intense sexual selection showing a smaller degree of allometry of tail ornaments. This study is consistent with theoretical models that predict no specific kind of allometric pattern for sexual and nonsexual characters.

Fine morphology of experimental tail streamers and flight manoeuvrability in the house martinDelichon urbica

Summary 1. Recent studies suggest that long tail streamers (narrow outermost tail feathers) of the barn swallow Hirundo rustica , Linnaeus have initially evolved purely via natural selection for enhanced manoeuvrability. According to an alternative view, streamers have evolved initially solely via sexual selection for costly signalling, and their slender profile is merely an adaptation reducing the aerodynamic cost of a long tail ornament. 2. In order to distinguish between these alternative hypotheses we performed a standardized flightmaze experiment, in which we imitated the initial elongation of outermost tail feathers in a streamer-less hirundine, the house martin Delichon urbica , Linnaeus, contrasting the effects on flight manoeuvrability from adding either a broad or a narrow piece of feather. 3. ‘Narrow-feathered’ house martins (which had initial tail streamers modelled on a natural streamer of the barn swallow) manoeuvred better than ‘broad-feathered’ house martins (which had the natural shape of tips of experimentally elongated outermost tail feathers left unchanged), independent of elongation of the feather. 4. A small elongation of outermost tail feathers did not significantly improve manoeuvrability either in the case of ‘narrow-feathered’ or ‘broad-feathered’ birds. 5. These results suggest that it is the slender shape, but not elongation of streamers that is important for manoeuvrability, and thus streamer elongation is better explained by the sexual-selection than the improved-manoeuvrability hypothesis. We discuss hypothetical scenarios for evolution of hirundine tail streamers.

Notes on the Natural History of Pseudocerastes urarachnoides (Squamata: Viperidae)

An Iranian viper, Pseudocerastes urarachnoides , was collected alive during fieldwork in April 2008. The viper was transferred to the lab where many observations were made of its biology, behavior, feeding, habitat and distribution. During this survey we verified the previous speculation that its tail ornament (knob-like structure) is used as a lure to attract prey. Distribution was extended from Kermanshah Province to Khuzestan Province.

Male barn swallows use different resource allocation rules to produce ornamental tail feathers

Sexual ornaments compete for resources with other functional traits. Such resource allocation trade-offs should ensure the honesty of sexual ornaments according to the Zahavi’s handicap principle. However, the existence of costly signals could not be enough to guarantee honesty if different individuals invest different proportions of their limited resources in ornaments. Then, a certain level of sexual signaling would correspond to several levels of individual condition. Here, we explore whether there are different resource allocation rules in tail feather ornaments between males within a barn swallow (Hirundo rustica) population and whether these different rules confer different viability to males. We assessed the proportion of resources invested in ornamental feathers compared with other functional feathers moulted and growing during the same period at expenses of the same resources. We found that 1) different males allocate a different proportion of resources to ornamental feathers in relation to functional feathers and this proportion is repeatable between years and 2) male survival likelihood decreased as the proportion of resources allocated to ornamental feathers increased. Survival costs associated with increased investments in ornaments can maintain the sexual signaling system honest at population level but do not preclude the existence of an array of different allocation rules between males. Thus, males with different viability can produce ornamental feathers of the same length. These results show that the relationship between male viability and ornament expression can be less straightforward than considered previously. Key words: barn swallow, honesty, resource allocation, sexual ornaments, tail feathers, tradeoff. [Behav Ecol]

Morphological characteristics of Cape sugarbirds (Promerops cafer) from Helderberg Nature Reserve

Cape sugarbirds (Promerops cafer) are the largest nectarivores in the Western Cape and feed almost exclusively on protea nectar and associated arthropods. Helderberg Nature Reserve, Western Cape, South Africa, has a large diversity of Protea and supports breeding sugarbirds. As part of a larger study, we captured sugarbirds using mist-nets during the breeding and non-breeding season at several sites in the Helderberg Nature Reserve, Western Cape, South Africa, from 1996 to 2000. From these data (n =283 males, 272 females), we found that in both sexes, individuals with longer tails have longer wings. Males were significantly larger in mass, culmen, head, tarsus, wing and tail length than females. Males with larger mass were larger in all morphometric measurements than those with smaller mass. Mate choice and territory defence may be based on wing and tail ornament displays of male sugarbirds, thus larger males with larger ornaments could benefit through greater breeding success than smaller males.

Patterns of morphological variation in two sexually dimorphic bird species with different tail shapes

Many studies have focused on tail ornamentation in birds, but not all tail shapes have been studied in depth. Graduated and pin tails have received less attention than forked tails, despite being more likely, in terms of aerodynamic theory, to be honest signals. We report morphological variation in live specimens of two sexually dimorphic passerines from the same site with different tail shapes: graduated (Cape sugarbird Promerops cafer) and pin (orange-breasted sunbird Antobaphes violacea). Coefficients of variation (CVs) were calculated for all morphological traits, both non-ornamental (range 1.91–5.72) and ornamental (range 5.83–21.71). Males and females did not differ in CV for any non-ornamental trait. Ornamental traits in males of both species were significantly more variable than all non-ornamental traits. Cape sugarbird ornamental traits were significantly more variable than those of orange-breasted sunbirds. The high levels of variation in graduated tails relative to pintails suggest that these traits have been driven mainly by sexual selection. In contrast, both constraining natural and multiple ornament selection could be responsible for the relatively low levels of variation in pintails. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 437–443.