Family Of Songbirds Research Articles

Punctuated evolution of bill morphology in the largest family of songbirds (Thraupidae)

Abstract We assessed correlations between speciation rate and bill morphology in an ecologically diverse and continental-scale songbird radiation, the tanagers (Thraupidae). Our analyses showed that bill size, shape, and their evolutionary rates are not correlated with speciation rate. However, we did find evidence that each axis of variation in bill morphology diversifies at speciation events interspersed with periods of gradual evolution, consistent with a punctuated equilibrium model of character change. To determine correlations, we incorporated a time-calibrated molecular phylogeny and high-resolution three-dimensional surface scans of bill structure from museum study skins. Overall, our findings suggest that bill size and shape diversify in association with the speciation process, but not through any effect on the rate of speciation. Previous studies have shown other traits, such as song, ecological niche, and plumage do influence speciation and, ultimately, species richness in tanagers.

The earliest record of bowerbirds (Passeriformes, Ptilonorhynchidae) from the Oligo-Miocene of northern Australia

The bowerbirds (Passeriformes, Ptilonorhynchidae) are a family of Australo-Papuan songbirds that are renowned for their unique bower-building behaviour. Prior to this study, the fossil record of Ptilonorhynchidae was limited to late Quaternary remains from Victoria, Australia. A new genus and species of bowerbird is described here from the late Oligocene (ca 26–23 Ma) deposits of the Riversleigh World Heritage Area, in Waanyi Country, Queensland, Australia. This fossil bowerbird is smaller than most extant species of bowerbirds, and represents the earliest known evidence of Ptilonorhynchidae, although its intrafamilial affinities remain uncertain pending additional material. A second, larger ptilonorhynchid is identified from the early Miocene (ca 16 Ma) of Riversleigh. These fossils considerably extend the temporal range of Ptilonorhynchidae, and indicate the presence of two species of bowerbirds in the Oligo-Miocene of northern Australia. The ages of these fossils are consistent with molecular estimates of the divergence time between Ptilonorhynchidae and its sister group, Climacteridae (Australo-Papuan treecreepers). The new bowerbird is the ninth species of passerine to be described from the pre-Pleistocene of Australia, and highlights the importance of the Riversleigh fossil deposits in our understanding of the early evolutionary history of passerines.Jacqueline M.T. Nguyen [jacqueline.nguyen@flinders.edu.au], Australian Museum Research Institute, 1 William Street, Sydney NSW 2010 Australia; College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide SA 5001 Australia; and South Australian Museum, North Terrace, Adelaide SA 5000 Australia.

Widespread convergent morphological evolution within the largest family of songbirds.

Although convergence is a common evolutionary phenomenon, few studies have quantified its prevalence across a large, densely sampled clade. Large-scale phylogenies and the advent of novel computational methods facilitate more robust identification of convergent events and their statistical significance. The tanagers (Aves: Thraupidae), the largest family of songbirds, offer an excellent opportunity to study the extent of phenotypic convergence in response to similar ecological pressures on a continental scale. To investigate convergence in the group, we used the largest phylogenetic and multivariate morphological dataset to date for the clade. First, we used phylogenetic comparative analyses to show a correlation between diet and aspects of bill shape. We then investigated our dataset for the presence and magnitude of convergent events and assessed significance through simulations and modeling analyses. Overall, we found that around half (45.3%) of species and clades we tested have converged in morphological space more than would be expected by chance alone. Our study shows that across Thraupidae, various bill shapes have evolved convergently to fill multiple distinct sections of ecological niche space, reflecting a signal of ecological opportunity and structural constraints.

Loss of complex female song but not duetting in the ancestors of Carolina wrens

AbstractFemale singing and coordinated male–female duetting are often but not always found in the same species. Both behaviors are more common in tropical than temperate songbirds, but few studies have differentiated between the factors selecting for each. Here we investigate the evolution of female vocal complexity and male–female vocal coordination in Carolina wrens (Thryothorus ludovicianus), one of the few non‐tropical members of a songbird family (Troglodytidae) that is well known for producing coordinated male–female duets. Female Carolina wrens are not known to sing; rather, they produce relatively simple, sex‐specific chatters, often during territorial encounters. We analyzed field recordings to show that females coordinate these chatters with male songs at rates similar to those observed in some tropical duetting wren species. We then used phylogenetic comparative methods to show that the evolutionary ancestors of Carolina wrens had female songs that were more acoustically complex than the vocalizations of current females, suggesting past selection against female vocal complexity. Levels of vocal coordination with males, in contrast, have changed relatively little from those of tropical ancestors. Our results suggest that these two aspects of female behavior, acoustic complexity and vocal coordination with males, have evolved independently and have different functions in communication.

A near-complete and time-calibrated phylogeny of the Old World flycatchers, robins and chats (Aves, Muscicapidae)

The Old World flycatchers, robins and chats (Aves, Muscicapidae) are a diverse songbird family with over three hundred species. Despite continuous efforts over the past two decades, there is still no comprehensive and well-resolved species-level phylogeny for Muscicapidae. Here we present a supermatrix phylogeny that includes all 50 currently recognized genera and ca. 92% of all the species, built using data from up to 15 mitochondrial and 13 nuclear loci. In addition to assembling nucleotide sequences available in public databases, we also extracted sequences from the genome assemblies and raw sequencing reads from GenBank and included a few unpublished sequences. Our analyses resolved the phylogenetic position for several previously unsampled taxa, for example, the Grand Comoro Flycatcher Humblotia flavirostris, the Collared Palm Thrush Cichladusa arquata, and the Taiwan Whistling-Thrush Myophonus insularis, etc. We also provide taxonomic recommendations for genera that exhibit paraphyly or polyphyly. Our results suggest that Muscicapidae diverged from Turdidae (thrushes and allies) in the early Miocene, and the most recent common ancestors for the four subfamilies (Muscicapinae, Niltavinae, Cossyphinae and Saxicolinae) all arose around the middle Miocene.

Evolution of song and color in island birds

Island birds are often less colorful and sing different songs than their mainland counterparts. Given that trade-offs can occur in the expression of costly sexually selected traits, it is not clear whether island species with less colorful plumage than their mainland counterparts have compensated with increased complexity of song structure. To examine potential trade-offs in sexually selected traits in island birds, we examined concurrent patterns of coloration and song structure in island and mainland (sub)species across 3 widespread and speciose songbird families: Fringillidae, Meliphagidae, and Monarchidae. Phylogenetically controlled analyses revealed a shift away from white plumage and toward melanin-based plumage in island (sub)species but only in the Meliphagidae. Contrary to our predictions, we found no evidence that song structure in island birds differed from their mainland counterparts. Although a number of inverse correlations were identified between song structure and plumage coloration when all birds were considered, this pattern became weaker when only island populations were examined. Instead, we found island size affected song structure leading to a lower number of syllables and lower minimum frequency on smaller islands. Birds on smaller islands also had reduced carotenoid plumage but this pattern was only significant in the Fringillidae. These results indicate that island environments can influence the evolution of both song and color in some taxa, but that selection is tempered by island size, rather than through correlated evolution across signaling modalities.

Contingency and determinism in the evolution of bird song sound frequency

Sexual signals are archetypes of contingent evolution: hyper-diverse across species, often evolving fast and in unpredictable directions. It is unclear to which extent their evolutionary unpredictability weakens deterministic evolution, or takes place bounded by deterministic patterns of trait evolution. We compared the evolution of sound frequency in sexual signals (advertisement songs) and non-sexual social signals (calls) across > 500 genera of the crown songbird families. Contrary to the acoustic adaptation hypothesis, we found no evidence that forest species used lower sound frequencies in songs or calls. Consistent with contingent evolution in song, we found lower phylogenetic signal for the sound frequency of songs than calls, which suggests faster and less predictable evolution, and found unpredictable direction of evolution in lineages with longer songs, which presumably experience stronger sexual selection on song. Nonetheless, the most important deterministic pattern of sound frequency evolution—its negative association with body size—was stronger in songs than calls. This can be explained by songs being longer-range signals than most calls, and thus using sound frequencies that animals of a given size produce best at high amplitude. Results indicate that sexual selection can increase aspects of evolutionary contingency while strengthening, rather than weakening, deterministic patterns of evolution.

Species diversification and ecomorphological evolution in the radiation of tanagers (Passeriformes: Thraupidae)

Abstract Ecological opportunity is hypothesized to cause an early burst of species diversification and trait evolution followed by a slowdown in diversification rates as niches are filled. Nonetheless, few studies have tested these predictions empirically with ecomorphological data at the large spatial scales relevant to most of biodiversity. Tanagers (Passeriformes: Thraupidae), the largest family of songbirds, show an early burst of species diversification and provide an excellent opportunity to test one of the hallmarks of adaptive radiation: rapid ecomorphological evolution. Here, we test for an early-burst pattern of a resource-exploiting trait (bill morphology) across the radiation of tanagers using a time-calibrated molecular phylogeny and high-resolution three-dimensional surface scans of bill structure from museum study skins. Using recently developed methods of multivariate trait evolution, we find evidence for a rapid burst of bill shape evolution early in the radiation of tanagers, followed by a subsequent decrease in rates toward the present. Likewise, we show that morphological disparity is distributed among (rather than within) subclades, indicating that most of the observed bill shape disparity evolved early in the radiation of tanagers and has slowed through time. The diversification dynamics of tanagers match patterns expected from adaptive radiation and the filling of ecomorphospace.

Bill size, bill shape, and body size constrain bird song evolution on a macroevolutionary scale

AbstractStudying macroevolutionary patterns of phenotypic variation and their driving forces in large radiations can shed light on how biodiversity is generated across broad spatiotemporal scales. In this study, we integrated song and morphological variation across more than 300 species representing the largest family of songbirds, the tanagers (Thraupidae), to uncover how morphological variables of the vocal tract combine to shape vocal evolution on a macroevolutionary scale. We found that body size correlated with multiple frequency parameters, concurring with past studies that show how body size constrains vocal evolution. Furthermore, bill size predicted multiple frequency and temporal song characters while bill shape was strongly associated with trill rates, suggesting that bill size and shape both constrain distinct elements of avian song independently of body size covariation. Our results demonstrate that the relationship between morphology and song exhibits modular variation when expanded to a macroevolutionary scale. Furthermore, our study emphasizes the need to consider multiple components of the avian vocal tract when exploring the macroevolutionary interplay of morphological traits and acoustic signals.

Breeding season length predicts duet coordination and consistency in Neotropical wrens (Troglodytidae).

Many animals produce coordinated signals, but few are more striking than the elaborate male-female vocal duets produced by some tropical songbirds. Yet, little is known about the factors driving the extreme levels of vocal coordination between mated pairs in these taxa. We examined evolutionary patterns of duet coordination and their potential evolutionary drivers in Neotropical wrens (Troglodytidae), a songbird family well known for highly coordinated duets. Across 23 wren species, we show that the degree of coordination and precision with which pairs combine their songs into duets varies by species. This includes some species that alternate their song phrases with exceptional coordination to produce rapidly alternating duets that are highly consistent across renditions. These highly coordinated, consistent duets evolved independently in multiple wren species. Duet coordination and consistency are greatest in species with especially long breeding seasons, but neither duet coordination nor consistency are correlated with clutch size, conspecific abundance or vegetation density. These results suggest that tightly coordinated duets play an important role in mediating breeding behaviour, possibly by signalling commitment or coalition of the pair to mates and other conspecifics.

Ravens parallel great apes in physical and social cognitive skills

Human children show unique cognitive skills for dealing with the social world but their cognitive performance is paralleled by great apes in many tasks dealing with the physical world. Recent studies suggested that members of a songbird family—corvids—also evolved complex cognitive skills but a detailed understanding of the full scope of their cognition was, until now, not existent. Furthermore, relatively little is known about their cognitive development. Here, we conducted the first systematic, quantitative large-scale assessment of physical and social cognitive performance of common ravens with a special focus on development. To do so, we fine-tuned one of the most comprehensive experimental test-batteries, the Primate Cognition Test Battery (PCTB), to raven features enabling also a direct, quantitative comparison with the cognitive performance of two great ape species. Full-blown cognitive skills were already present at the age of four months with subadult ravens’ cognitive performance appearing very similar to that of adult apes in tasks of physical (quantities, and causality) and social cognition (social learning, communication, and theory of mind). These unprecedented findings strengthen recent assessments of ravens’ general intelligence, and aid to the growing evidence that the lack of a specific cortical architecture does not hinder advanced cognitive skills. Difficulties in certain cognitive scales further emphasize the quest to develop comparative test batteries that tap into true species rather than human specific cognitive skills, and suggest that socialization of test individuals may play a crucial role. We conclude to pay more attention to the impact of personality on cognitive output, and a currently neglected topic in Animal Cognition—the linkage between ontogeny and cognitive performance.

Speciation rates are correlated with changes in plumage color complexity in the largest family of songbirds.

Although evolutionary theory predicts an association between the evolution of elaborate ornamentation and speciation, empirical evidence for links between speciation and ornament evolution has been mixed. In birds, the evolution of increasingly complex and colorful plumage may promote speciation by introducing prezygotic mating barriers. However, overall changes in color complexity, including both increases and decreases, may also promote speciation by altering the sexual signals that mediate reproductive choices. Here, we examine the relationship between complex plumage and speciation rates in the largest family of songbirds, the tanagers (Thraupidae). First, we test whether species with more complex plumage coloration are associated with higher speciation rates and find no correlation. We then test whether rates of male or female plumage color complexity evolution are correlated with speciation rates. We find that elevated rates of plumage complexity evolution are associated with higher speciation rates, regardless of sex and whether species are evolving more complex or less complex ornamentation. These results extend to whole-plumage color complexity and regions important in signaling (crown and throat) but not nonsignaling regions (back and wingtip). Our results suggest that the extent of change in plumage traits, rather than overall values of plumage complexity, may play a role in speciation.

Whole-genome analysis across 10 songbird families within Sylvioidea reveals a novel autosome-sex chromosome fusion.

Sex chromosomes in birds have long been considered to be extremely stable. However, this notion has lately been challenged by findings of independent autosome-sex chromosome fusions within songbirds, several of which occur within a single clade, the superfamily Sylvioidea. To understand what ecological and evolutionary processes drive changes in sex chromosome systems, we need complete descriptions of sex chromosome diversity across taxonomic groups. Here, we characterize the sex chromosome systems across Sylvioidea using whole-genome data of species representatives of 10 different families, including two published and eight new genomes. We describe a novel fusion in the family Cisticolidae (represented by Cisticola juncidis) involving a part of chromosome 4. We also confirm the previously identified fusion between chromosome Z and a part of chromosome 4A in all 10 families and show that fusions involving parts of chromosomes 3 and 5 are not found outside the families where they were first discovered (Alaudidae and Panuridae). These findings add to the complexity of the sex chromosome system in Sylvioidea, where four independent autosome-sex chromosome fusions have now been identified.

Asymmetries in reproductive anatomy: insights from promiscuous songbirds

Abstract Directional asymmetry in gonad size is commonly observed in vertebrates and is particularly pronounced in birds, where the left testis is frequently larger than the right. The adaptive significance of directional asymmetry in testis size is poorly understood, and whether it extends beyond the testes (i.e. side-correspondent asymmetry along the reproductive tract) has rarely been considered. Using the Maluridae, a songbird family exhibiting variation in levels of sperm competition and directional testis asymmetry, yet similar in ecology and life history, we investigated the relative roles of side-correspondence and sperm competition on male reproductive tract asymmetry at both inter- and intraspecific levels. We found some evidence for side-correspondent asymmetry. Additionally, sperm competition influenced directional asymmetry at each end of the reproductive tract: species experiencing higher levels of sperm competition had a relatively larger right testis and relatively more sperm in the right seminal glomerus. Within red-backed fairy-wrens (Malurus melanocephalus), auxiliary males had relatively more sperm in the left seminal glomerus, in contrast to a right-bias asymmetry throughout the reproductive tract in breeding males. Given that the number of sperm is important for competitive fertilization success, our results suggest that sperm competition shapes reproductive asymmetries beyond testis size, with likely functional consequences for male reproductive success.

A Morphological Integration Perspective on the Evolution of Dimorphism among Sexes and Social Insect Castes.

Many species have evolved alternate phenotypes, thus enabling individuals to conditionally produce phenotypes that are favorable for reproductive success. Examples of this phenomenon include sexual dimorphism, alternative reproductive strategies, and social insect castes. While the evolutionary functions and developmental mechanisms of dimorphic phenotypes have been studied extensively, little attention has focused on the evolutionary covariance between each phenotype. We extend the conceptual framework and methods of morphological integration to hypothesize that dimorphic traits tend to be less integrated between sexes or social castes. In the case of social insects, we describe results from our recent study of an ant genus in which workers have major and minor worker castes that perform different behavioral repertoires in and around the nest. In the case of birds, we describe a new analysis of a family of songbirds that exhibits plumage coloration that can differ greatly between males and females, with apparently independent changes in each sex. Ant head shape, which is highly specialized in each worker caste, was weakly integrated between worker castes, whereas thorax shape, which is more monomorphic, was tightly integrated. Similarly, in birds, we found a negative association between dimorphism and the degree of integration between sexes. We also found that integration decreased in fairy wrens (Malurus) for many feather patches that evolved greater dichromatism. Together, this suggests that the process of evolving increased dimorphism results in a decrease in integration between sexes and social castes. We speculate that once a mechanism for dimorphism evolves, that mechanism can create independent variation in one sex or caste upon which selection may act.

Rufous‐capped Warblers Basileuterus rufifrons show seasonal, temporal and annual variation in song use

In the majority of songbird species, males have repertoires of multiple song types used for mate attraction and territory defence. The wood‐warblers (family Parulidae) are a diverse family of songbirds in which males of many migratory species use different song types or patterns of song delivery (known as ‘singing modes’) depending on context. The vocal behaviour of most tropical resident warblers remains undescribed, although these species differ ecologically and behaviourally from migratory species, and may therefore differ in their vocal behaviour. We test whether male Rufous‐capped Warblers Basileuterus rufifrons use distinct singing modes by examining song structure and context‐dependent variation in their songs. We recorded multiple song bouts from 50 male Warblers in a Costa Rican population over 3 years to describe seasonal, diel and annual variation in song structure and vocal behaviour. We found that Rufous‐capped Warbler songs are complex, with many syllable types shared both within and between males’ repertoires. Males varied their song output depending on context: they sang long songs at a high rate at dawn and during the breeding season, and shortened songs in the presence of a vocalizing female mate. Unlike many migratory species, Rufous‐capped Warblers do not appear to have different singing modes; they did not change the song variants used or the pattern of song delivery according to time of day, season or female vocal activity. Our research provides the first detailed vocal analysis of any Basileuterus warbler species, and enhances our understanding of the evolution of repertoire specialization in tropical resident songbirds.

Contrasting impacts of competition on ecological and social trait evolution in songbirds.

Competition between closely related species has long been viewed as a powerful selective force that drives trait diversification, thereby generating phenotypic diversity over macroevolutionary timescales. However, although the impact of interspecific competition has been documented in a handful of iconic insular radiations, most previous studies have focused on traits involved in resource use, and few have examined the role of competition across large, continental radiations. Thus, the extent to which broad-scale patterns of phenotypic diversity are shaped by competition remain largely unclear, particularly for social traits. Here, we estimate the effect of competition between interacting lineages by applying new phylogenetic models that account for such interactions to an exceptionally complete dataset of resource-use traits and social signaling traits for the entire radiation of tanagers (Aves, Thraupidae), the largest family of songbirds. We find that interspecific competition strongly influences the evolution of traits involved in resource use, with a weaker effect on plumage signals, and very little effect on song. Our results provide compelling evidence that interspecific exploitative competition contributes to ecological trait diversification among coexisting species, even in a large continental radiation. In comparison, signal traits mediating mate choice and social competition seem to diversify under different evolutionary models, including rapid diversification in the allopatric stage of speciation.

The role of sexual and natural selection in shaping patterns of sexual dichromatism in the largest family of songbirds (Aves: Thraupidae).

Males and females can be under different evolutionary pressures if sexual and natural selection is differentially operating in each sex. As a result, many species have evolved sexual dichromatism, or differences in coloration between sexes. Although sexual dichromatism is often used as an index of the magnitude of sexual selection, sexual dichromatism is a composite trait. Here, we examine the evolution of sexual dichromatism in one of the largest and most ecologically diverse families of birds, the tanagers, using the avian visual perspective and a species-level phylogeny. Our results demonstrate that the evolutionary decreases of sexual dichromatism are more often associated with larger and more frequent changes in male plumage coloration, and evolutionary increases are not more often associated with larger changes in either sex. Furthermore, we show that the crown and ventral plumage regions are correlated with sexual dichromatism in males, and that only male plumage complexity is positively correlated with sexual dichromatism. Finally, we demonstrate that light environment is important in shaping both plumage brilliance and complexity. By conducting a multilevel analysis of plumage evolution in males and females, we show that sexual dichromatism evolves via a mosaic of sexual and natural selection in both sexes.

A genus-level classification of the family Thraupidae (Class Aves: Order Passeriformes).

The tanagers (Thraupidae) are a major component of the Neotropical avifauna,and vary in plumage colors, behaviors, morphologies, and ecologies.Globally, they represent nearly 4% of all avian species and are the largest family of songbirds. However, many currently used tanager genera are not monophyletic, based on analyses of molecular data that have accumulated over the past 25 years. Current genus-level classifications of tanagers have not been revised according to newly documented relationships of tanagers for various reasons: 1) the lack of a comprehensive phylogeny, 2) reluctance to lump existing genera into larger groups, and 3) the lack of available names for newly defined smaller groups. Here, we present two alternative classifications based on a newly published comprehensive phylogeny of tanagers. One of these classifications uses existing generic names, but defines them broadly. The other, which we advocate and follow here, provides new generic names for more narrowly defined groups. Under the latter, we propose eleven new genera (Asemospiza, Islerothraupis, Maschalethraupis, Chrysocorypha, Kleinothraupis, Castanozoster, Ephippiospingus, Chionodacryon, Pseudosaltator, Poecilostreptus, Stilpnia), and resurrect several generic names to form monophyletic taxa. Either of these classifications would allow taxonomic authorities to reconcile classification with current understanding of tanager phylogenetic relationships. Having a more phylogenetically accurate classification for tanagers will facilitate the study and conservation of this important Neotropical radiation of songbirds.

SONGBIRD – AN INNOVATIVE UAS COMBINING THE ADVANTAGES OF FIXED WING AND MULTI ROTOR UAS

Abstract. This paper describes a family of innovative fixed wing UAS with can vertical take off and land – the SONGBIRD family. With nominal payloads starting from 0.5 kg they can take off and land safely like a multi-rotor UAV, removing the need for an airstrip for the critical phases of operation. A specially designed flight controller allows stable flight at every point of the transition phase between VTOL and fixed wing mode. Because of this smooth process with a all time stable flight, very expensive payload like hyperspectral sensors or advanced optical cameras can be used. Due to their design all airplanes of the SONGBIRD family have excellent horizontal flight properties, a maximum speed of over 110 km/h, good gliding properties and long flight times of up to 1 h. Missions were flown in wind speeds up to 18 m/s. At every time of the flight it is possible to interrupt the mission and hover over a point of interest for detail investigations. The complete flight, including take-off and landing can be performed by autopilot. Designed for daily use in professional environments, SONGBIRDs are built out of glass-fibre and carbon composites for a long service life. For safe operations comprehensive security features are implemented, for example redundant flight controllers and sensors, advanced power management system and mature fail safe procedures. The aircraft can be dismantled into small parts for transportation. SONGBIRDS are available for different pay loads, from 500 g to 2 kg. The SONGBIRD family are interesting tools combining the advantages of multi-copter and fixed wing UAS.