Oscine Research Articles

Learning mimetic cuckoo call innovations from neighbors in a Chinese songbird

Some oscine passerines incorporate heterospecific sounds into their repertoires, including vocalizations of other bird species, sounds of other fauna, and even anthropogenic sounds, through vocal mimicry. However, few studies have investigated whether mimics learn heterospecific sounds from model species or from conspecific tutors. Here, we investigate mimicry acquisition using innovation in Cuculidae calls imitated by the Chinese blackbird (Turdus mandarinus). If the mimicry innovation arises and spreads among several neighbors and is not produced by model species, the mimicry must be acquired partially from conspecifics. We found that: (1) Cuculidae calls imitated by blackbirds were reasonably accurate, but with some differences between mimetic and real calls in acoustic structures. (2) We identified four unique mimetic units (mimicry innovation or copy errors), and these units only occurred at certain sites and were shared by several neighbors. In aggregate, frequency parameters (the first principal component) of unique mimetic units were higher than usual mimetic units (p < 0.001). Our findings provide further evidence that mimetic units can be partially learnt from conspecifics based on four cases of unique mimetic units. Our study and approach provide a reference and theoretical basis for the future understanding of social learning and development of vocal mimicry.

Passerine sister clade comparisons reveal variable macroevolutionary outcomes of interhemispheric dispersal.

Dispersal events offer a unique window into macroevolutionary processes, especially with respect to the effects of competition on diversification. Empirical studies testing alternative predictions of competitive effects are often limited in either geographic or phylogenetic scale. Here, we tested some of these hypotheses by comparing an assemblage of 16 oscine passerine clades, representing independent dispersal events into the Western Hemisphere, to their sister clades in the Eastern Hemisphere. We also compared the diversity of this assemblage of clades to an older, incumbent passerine clade in the Western Hemisphere, the suboscines. Specifically, we tested for ecological opportunity and incumbency-mediated constraints by analysis of clade-specific morphological disparities and rates of evolution relative to dispersal history. While there was no consistent outcome of oscine dispersal and macroevolution in the Western Hemisphere relative to their Eastern Hemisphere sister groups, most clades supported a role for ecological opportunity or incumbency effects, and such effects were better explained by differences in species accumulation than by differences in rates of trait evolution or colonization timing. This general pattern was not evident when comparing the entire oscine assemblage of the Western Hemisphere to the incumbent suboscine radiation; oscines and suboscines occupy comparable regions of functional trait diversity and, despite higher rates of trait evolution in oscines, these observations were consistent with simulated null expectations. This result suggests that oscine and suboscine assemblages may have evolved in relative isolation for a significant fraction of their history.

Song system neuroanatomy, and immediate early gene expression in a finch species with extensive male and female song.

Birdsong is a relatively well-studied behavior, both due to its importance as a model for vocal production learning and as an intriguing complex social behavior. Until the last few decades, work on birdsong focused almost exclusively on males. However, it is now widely accepted that female song not only exists, but is fairly common throughout the oscine passerines. Despite this, and the large number of researchers who have begun exploring female song in the field, researchers in the lab have been slow to adopt model species with female song. Studying female song in the lab is critical for our understanding of sex-specific factors in the physiology controlling this fascinating behavior. Additionally, as a model for vocal production learning in humans, understanding the mechanistic and neuroendocrine control of female song is clearly important. In this study, we examined the red-cheeked cordon bleu (RCCB), an Estrildid finch species with extensive female song. Specifically, we found that there were no significant sex differences in circulating levels of testosterone and progesterone, nor in song production rate. There were no significant differences in cell densities in the three nuclei of the song control system we examined. Additionally, the volume of the robust nucleus of the arcopallium was not significantly different and we report the smallest sex difference in HVC yet published in a songbird. Finally, we demonstrated similar levels of motor driven immediate early gene expression in both males and females after song production.

The dynamics behind diversity in suboscine songs.

Vocal behavior plays a crucial evolutionary role. In the case of birds, song is critically important in courtship, male-male competition and other key behaviors linked to reproduction. However, under natural conditions, a variety of avian species live in close proximity and share an 'acoustic landscape'. Therefore, they need to be able to differentiate their calls or songs from those of other species and also from those of other individuals of the same species. To do this efficiently, birds display a remarkable diversity of sounds. For example, in the case of vocal learners, such as oscine passerines (i.e. songbirds), complex sequences and subtle acoustic effects are produced through the generation of complex neuromuscular instructions driving the vocal organ, which is remarkably conserved across approximately 4000 oscine species. By contrast, the majority of the sister clade of oscines, the suboscine passerines, are thought not to be vocal learners. Despite this, different suboscine species can generate a rich variety of songs and quite subtle acoustic effects. In the last few years, different suboscine species have been shown to possess morphological adaptations that allow them to produce a diversity of acoustic characteristics. Here, we briefly review the mechanisms of sound production in birds, before considering three suboscine species in more detail. The examples discussed in this Review, integrating biological experiments and biomechanical modeling using non-linear dynamical systems, illustrate how a morphological adaptation can produce complex acoustic properties without the need for complex neuromuscular control.

Yellow Cardinal (Gubernatrix cristata) males respond more strongly to local than to foreign dialects

Bird song is a culturally transmitted behavioural trait strongly tied to territory defence and mate attraction in oscine passerines. Divergent song variations can appear in different populations of the same species as a consequence of multiple factors generating geographically distinct songs also termed dialects. Most studies show that males react more strongly towards local dialects, potentially as a by‐product of evolutionary divergence between populations, although other hypotheses have been suggested. In addition, females are hypothesized to show stronger responses to local songs as this may lead to greater reproductive success. In this context, song may become a prezygotic barrier for reproduction. The Yellow CardinalGubernatrix cristatais an endangered species of the South American thorny shrubland that has suffered from population fragmentation due to habitat destruction and its capture for the illegal wildlife trade. Genetically different groups that sing their own dialect have been studied in the context of a conservation programme that intends to restore and preserve natural populations by releasing individuals that are recovered from the illegal pet market back into their area of origin. Although dialects have been identified, it remains unknown whether there is vocal recognition between the populations. In this study, we performed playback experiments in two populations and found that male Yellow Cardinals reacted more strongly to the local dialect, although the foreign dialect was still recognized. This information is important as it is not always possible to genetically assign an individual to its geographical origin before release, which could contribute to a secondary contact scenario where dialects play a critical role for settlement and reproduction.

Oligo-Miocene radiation within South-west Pacific arc terranes underpinned repeated upstream continental dispersals in pigeons (Columbiformes)

AbstractUpstream colonizations from islands to continents have played an important role in two major global bird radiations: the oscine passerines and the pigeons. Here, we investigate insular diversification and upstream dispersal dynamics of pigeons (Columbiformes) within the Indo-Australian Archipelago using a supermatrix fossil-calibrated phylogeny and model-based biogeographical analyses. These analyses show that the islands of Melanesia, now centred on New Guinea and considered separately from Australia, have been a centre of pigeon diversification since the Eocene–Oligocene transition (~34 Mya). Geological reconstructions are concordant in suggesting that arc terranes and continental ribbon fragments that underpin the contemporary Melanesian region might have formed extensive archipelagos for much of the Oligocene and Miocene. These islands are also inferred to have functioned as a net source of pigeon lineages for Asia and especially Australia. Arboreal fruit-eating pigeons have colonized nearby continents on multiple occasions yet show little evidence of subsequent radiation. Insular terrestrial pigeons have been largely unable to colonize Asia, and a single Miocene colonization of Australia preceded an endemic radiation. Upstream dispersal may well be a frequent process in the history of the Indo-Australian Archipelago and surrounds, however ecological and environmental factors likely place strong constraints on its success and evolutionary outcomes.

Local and range-wide distribution of song types suggest Ovenbirds (Seiurus aurocapilla) have song neighborhoods but not macro-dialects

The song systems of oscine passerines (songbirds) are complex and diverse. Because songs are used for both mate attraction and territory defense and are therefore important signals for survival and reproduction, comprehensive knowledge of within and among species song structure and distribution is informative for understanding the evolution of song repertoires and vocal behaviour. In this study, we explored variation in the song structure of the Ovenbird (Seiurus aurocapilla), a widespread warbler (Family Parulidae) found in North American forests. We analyzed recordings from the 2021 breeding season to assess song type variation at a local (n ​= ​158 birds; Sault Ste. Marie, ON) and breeding range scale (n ​= ​512 birds; eBird). We characterized the local song types and tested whether Ovenbirds share song types with their neighbors more often than expected by chance. We then characterized song types of Ovenbirds across the breeding range to determine whether any geographic pattern of song clustering exists (i.e., macro-dialects). We found 10 distinct song types and some evidence for song type clustering at the local study site (i.e., song neighborhoods). We found 7 of those 10 song types throughout the breeding range and identified an additional 24 types that were not recorded in our local population. We found no evidence for song dialects across the Ovenbird breeding range. This study contributes to our understanding of Ovenbird song while simultaneously adding to our understanding of geographic structuring of warbler repertoires. Our work contributes to delineating a more comprehensive understanding of factors affecting dialect development for this diverse group of songbirds.

Estimating heritability of song considering within-individual variance in a wild songbird: The collared flycatcher

Heritable genetic variation is a prerequisite for adaptive evolution; however, our knowledge about the heritability of plastic traits, such as behaviors, is scarce, especially in wild populations. In this study, we investigated the heritability of song traits in the collared flycatcher (Ficedula albicollis), a small oscine passerine with complex songs involved in sexual selection. We recorded the songs of 81 males in a natural population and obtained various measures describing the frequency, temporal organization, and complexity of each song. As we had multiple songs from each individual, we were able to statistically account for the first time for the effect of within-individual variance on the heritability of song. Heritability was calculated from the variance estimates of animal models relying on a genetic similarity matrix based on Single Nucleotide Polymorphism screening. Overall, we found small additive genetic variance and heritability values in all song traits, highlighting the role of environmental factors in shaping bird song.

A rallid ballad: Communal signaling is correlated with year-round territoriality in the most duet-rich family of birds (Gruiformes: Rallidae)

Abstract Duetting, in which 2 or more individuals call in coordinated unison, is common in birds, yet most research investigating the function of avian duets has focused only on oscine passerines. However, we have discovered that duetting occurs in 61 species (59%) in the family Rallidae (rails), one of the highest known rates in any bird clade, and that rail duets are also significantly associated with year-round territoriality and habitat type. We applied a comparative approach to study the occurrence of duetting relative to socio-ecological traits and call properties in 103 rail species, with the prediction that duetting rails produce low-frequency calls that spread well over short distances in densely vegetated habitats. Using a model correcting for phylogenetic signal, we found that duetting is the ancestral state in Rallidae, and that duetting rails show a trending effect for being sedentary and nonmigratory. Contrary to our predictions, there was no significant correlation between rail duetting and social bond length, breeding system, breeding latitude from the equator, or sexual dimorphism, as year-round territoriality and forest or heterogeneous habitats were the strongest predictors of duets. Despite the prevalence of duetting in Rallidae, few studies have tested duet functions such as territory defense in this family, and our comparative phylogenetic study lays the groundwork for future research, as little remains known about the behavioral ecology and vocal interactions of many rails.

Selective alarm call mimicry in the sexual display of the male superb lyrebird (Menura novaehollandiae)

Despite much research on mimicry, little is known about the ecology of dynamic mimetic signals involving mimicry of multiple species. Some of the most conspicuous examples of phenotypically plastic mimicry are produced by oscine passerines, where vocal production learning enables some species to mimic multiple models and flexibly adjust what they mimic and when. While singing from a perch, male superb lyrebirds (Menura novaehollandiae) accurately imitate multiple songs and calls of over 20 species of bird. However, at key moments within their multimodal displays performed on display arenas on the forest floor, males mimic a small number of mobbing-alarm calls creating the acoustic illusion of a mixed-species mobbing flock (‘D-song’). Using observations from camera footage and a field-based playback experiment, we tested six hypotheses for alarm call model selection within D-song. Mimicked species were remarkably invariant, with 79% of D-song made up of imitations of just three different bird species. Males did not mimic the most common species in their general environment, but neither did they mimic rare species. Instead, males imitated the mobbing-alarm calls of heterospecific birds that foraged on or near the forest floor. Indeed, males primarily mimicked the alarm calls of heterospecific species that foraged alongside lyrebirds and were likely to appear together in experimentally-induced, terrestrial mobbing flocks. These findings support the hypothesis that males mimic a cue of a terrestrial predatory threat to lyrebirds, most likely to exploit the antipredator behaviour of female lyrebirds. Our study illustrates the importance of investigating the drivers of model selection in dynamic multi-model mimicry.

Male superb lyrebirds mimic functionally distinct heterospecific vocalizations during different modes of sexual display

Mimicry has long been a focus of research, but little is known about how and why many species of bird incorporate imitations of heterospecific sounds into their vocal displays. Crucial to understanding mimetic song is determining what sounds are mimicked and in what contexts such mimicry is produced. The superb lyrebird, Menura novaehollandiae, is a large oscine passerine with a lek-like mating system. Both sexes are accurate and versatile vocal mimics of the vocalizations of other species, but little is known about how males deploy their repertoire of mimicked sounds across contexts. Using extended focal watches, we recorded adult males displaying during the breeding season. We found that males mimicked heterospecific songs and nonalarm calls during ‘recital’ displays usually performed while they were perched and visually inconspicuous. In contrast, during visually conspicuous ‘dance’ displays, commonly performed on display mounds, males only mimicked heterospecific alarm calls. While much rarer than recital displays, dance displays were associated with the final stages of mate choice preceding copulation. These results provide the first evidence of any species varying its repertoire of mimicked sounds with different sexual contexts. Previous work suggests that mimicry in dance displays functions deceptively to manipulate the antipredator responses of females during the final stages of courtship. However, the structure and context of recital mimicry closely resembles the sexual advertisement song performed by nonmimicking songbirds. Given the importance of mimicry in the acoustic ecology of lyrebirds, our results suggest that with recital song males advertise the quality of their mimicry as it likely benefits both male and female offspring. Our finding that male superb lyrebirds mimic functionally distinct heterospecific vocalizations during different modes of courtship suggests that the evolution and maintenance of avian vocal displays are more complex than previously thought.

Like Father Like Son: Cultural and Genetic Contributions to Song Inheritance in an Estrildid Finch.

Social learning of vocalizations is integral to song inheritance in oscine passerines. However, other factors, such as genetic inheritance and the developmental environment, can also influence song phenotype. The relative contributions of these factors can have a strong influence on song evolution and may affect important evolutionary processes such as speciation. However, relative contributions are well-described only for a few species and are likely to vary with taxonomy. Using archived song data, we examined patterns of song inheritance in a domestic population of Java sparrows (Lonchura oryzivora), some of which had been cross-fostered. Six-hundred and seventy-six songs from 73 birds were segmented and classified into notes and note subtypes (N = 22,972), for which a range of acoustic features were measured. Overall, we found strong evidence for cultural inheritance of song structure and of the acoustic characteristics of notes; sons’ song syntax and note composition were similar to that of their social fathers and were not influenced by genetic relatedness. For vocal consistency of note subtypes, a measure of vocal performance, there was no apparent evidence of social or genetic inheritance, but both age and developmental environment influenced consistency. These findings suggest that high learning fidelity of song material, i.e., song structure and note characteristics, could allow novel variants to be preserved and accumulate over generations, with implications for evolution and conservation. However, differences in vocal performance do not show strong links to cultural inheritance, instead potentially serving as condition dependent signals.

Avian vocalisations: the female perspective.

Research on avian vocalisations has traditionally focused on male song produced by oscine passerines. However, accumulating evidence indicates that complex vocalisations can readily evolve outside the traditional contexts of mate attraction and territory defence by male birds, and yet the previous bias towards male song has shaped - and continues to shape - our understanding of avian communication as a whole. Accordingly, in this review we seek to address this imbalance by synthesising studies on female vocalisations from across signalling contexts throughout the Aves, and discuss the implications of recent empirical advances for our understanding of vocalisations in both sexes. This review reveals great structural and functional diversity among female vocalisations and highlights the important roles that vocalisations can play in mediating female-specific behaviours. However, fundamental gaps remain. While there are now several case studies that identify the function of female vocalisations, few quantify the associated fitness benefits. Additionally, very little is known about the role of vocal learning in the development of female vocalisations. Thus, there remains a pressing need to examine the function and development of all forms of vocalisations in female birds. In the light of what we now know about the functions and mechanisms of female vocalisations, we suggest that conventional male-biased definitions of songs and calls are inadequate for furthering our understanding of avian vocal communication more generally. Therefore, we propose two simple alternatives, both emancipated from the sex of the singer. The first distinguishes song from calls functionally as a sexually selected vocal signal, whilst the second distinguishes them mechanistically in terms of their underlying neurological processes. It is clear that more investigations are needed into the ultimate and proximate causes of female vocalisations; however, these are essential if we are to develop a holistic epistemology of avian vocal communication in both sexes, across ecological contexts and taxonomic divides.

New feather mites of the Nycteridocaulus generic group (Acariformes: Proctophyllodidae) from passerines (Passeriformes) in Panama.

Three new feather mite species of the Nycteridocaulus generic group (Proctophyllodidae: Proctophyllodinae) are described from passerines in Panama: Atrichophyllodes myrmotherulae sp. n. from the Slaty Antwren, Myrmotherula schisticolor (Lawrence) (Thamnophilidae), Nycteridocaulus apanaskevichi sp. n. from the Grey-breasted Wood Wren, Henicorhina leucophrys (Tschudi) (Troglodytidae), and N. empidonicus sp. n. from the Yellowish Flycatcher Empidonax flavescens Lawrence (Tyrannidae). Nycteridocaulus apanaskevichi, presenting the second record of the genus from a host of oscine passerines, differs from N. guaratubensis Hernandes, 2014 in having the anterolateral extensions of the prodorsal shield rounded and the hysteronotal shield lacking any ornamentation. Males of N. empidonicus differ from N. myiobius Mironov, 2017 in having the supranal concavity open posteriorly and tarsus IV with rounded apical process; and females are distinguished by macrosetae h2 having long filiform apices. Males of A. myrmotherulae most clearly differ from A. mentalis Hernandes et al. 2007 in having the terminal lamellae rectangular and tarsus IV with triangular ventral process, and females are distinguished in having a noticeably longer idiosoma, 400-430 μm long. Comments on systematics and host associations of the genera Atrichophyllodes and Nycteridocaulus are provided.

Use of simple graded signals in the long-distance vocal communication of a forest thrush (Catharus fuscescens)

ABSTRACT I investigated the use of simple graded structures (i.e. ‘calls’) in long-distance vocal communication among territorial forest-dwelling Catharus fuscescens – an oscine passerine that also possesses a complex song. Two experiments were conducted: (1) Nests were threatened in three different contexts to test the effect of increasing motivation on three response variables (call form, rate, amplitude), and (2) a playback study was undertaken to quantify the accomplishments of graded call structures on territory-holders. Results from the two experiments showed that long-distance communication in the focal species is dependent on two concurrent aspects of communication: (1) Acoustic cues to signaller motivation via call rate, (2) spectral cues that reveal directivity – either precisely or imprecisely – that complement the perception of signaller location via distance assessment (ranging). Simultaneously, amplitude and bandwidth are adjusted to beam signals across various distance intervals. Therefore, to affect conspecific behaviour, a signaller can alter vocal cues to manipulate an assessor’s perception of signaller location while revealing motivation. This study reveals the foundational components of short and long-distance communication with the use of simple graded calls by a forest-dwelling oscine passerine. It is similar to long-distance communication networks documented in some parrots, marine mammals, and primates.

Differential geographic patterns in song components of male Albert's lyrebirds.

Geographic variation in bird song has received much attention in evolutionary studies, yet few consider components within songs that may be subject to different constraints and follow different evolutionary trajectories. Here, we quantify patterns of geographic variation in the socially transmitted “whistle” song of Albert's lyrebirds (Menura alberti), an oscine passerine renowned for its remarkable vocal abilities. Albert's lyrebirds are confined to narrow stretches of suitable habitat in Australia, allowing us to map likely paths of cultural transmission using a species distribution model and least cost paths. We use quantitative methods to divide the songs into three components present in all study populations: the introductory elements, the song body, and the final element. We compare geographic separation between populations with variation in these components as well as the full song. All populations were distinguishable by song, and songs varied according to the geographic distance between populations. However, within songs, only the introductory elements and song body could be used to distinguish among populations. The song body and final element changed with distance, but the introductory elements varied independently of geographic separation. These differing geographic patterns of within‐song variation are unexpected, given that the whistle song components are always produced in the same sequence and may be perceived as a temporally discrete unit. Knowledge of such spatial patterns of within‐song variation enables further work to determine possible selective pressures and constraints acting on each song component and provides spatially explicit targets for preserving cultural diversity. As such, our study highlights the importance for science and conservation of investigating spatial patterns within seemingly discrete behavioral traits at multiple levels of organization.

Development syndromes in New World temperate and tropical songbirds.

We studied avian development in 49 to 153 species of temperate and tropical New World passerine birds to determine how growth rates, and incubation and nestling periods, varied in relation to other life-history traits. We collected growth data and generated unbiased mass and tarsus growth rate estimates (mass n = 92 species, tarsus n = 49 species), and measured incubation period (n = 151) and nestling period (n = 153), which we analyzed with respect to region, egg mass, adult mass, clutch size, parental care type, nest type, daily nest predation rate (DMR), and nest height. We investigated covariation of life-history and natural-history attributes with the four development traits after controlling for phylogeny. Species in our lowland tropical sample grew 20% (incubation period), 25% (mass growth rate), and 26% (tarsus growth rate) more slowly than in our temperate sample. Nestling period did not vary with respect to latitude, which suggests that tropical songbirds fledge in a less well-developed state than temperate species. Suboscine species typically exhibited slower embryonic and post-embryonic growth than oscine passerines regardless of their breeding region. This pattern of slow development in tropical species could reflect phylogenetic effects based on unknown physiological attributes. Time-dependent nest mortality was unrelated to nestling mass growth rate, tarsus growth rate, and incubation period, but was significantly associated with nestling period. This suggests that nest predation, the predominant cause of nest loss in songbirds, does not exert strong selection on physiologically constrained traits, such as embryonic and post-embryonic growth, among our samples of temperate and lowland tropical songbird species. Nestling period, which is evolutionarily more labile than growth rate, was significantly shorter in birds exposed to higher rates of nest loss and nesting at lower heights, among other traits. Differences in life-history variation across latitudes provide insight into how unique ecological characteristics of each region influence physiological processes of passerines, and thus, how they can shape the evolution of life histories. While development traits clearly vary with respect to latitude, trait distributions overlap broadly. Life-history and natural history associations differ for each development trait, which suggests that unique selective pressures or constraints influence the evolution of each trait.

Ontogeny of vocal learning in a hummingbird

Hummingbirds have evolved to learn song from conspecifics independently of other bird clades that show this behaviour, such as parrots and oscine passerines. Little is known about how vocal learning occurs in hummingbirds. To determine the conditions necessary and sufficient for learning, we raised young Costa's hummingbirds, Calypte costae, in isolation in two experiments. The first experiment tested whether three pairs of males, raised either in silence or with only acoustic exposure to song, would produce wild-type song. They did not: each pair instead produced ‘isolate’ songs dissimilar to wild-type song. Each pair produced a unique isolate song with subtle differences from other pairs. Thus, exposure to song alone is insufficient to trigger learning. The second experiment tested whether individually housed males would learn songs when exposed to a live male model plus playback of song (1 h/day, 3 days/week, for 3 months). Seven of eight birds that heard Costa's-like songs learned to sing their tutor song. Each individual produced song that matched idiosyncratic features of the individual songs played to them, demonstrating attention to, and learning of the exact acoustic stimuli received. Two control birds exposed to acoustically dissimilar Anna's hummingbird, Calypte anna, song developed isolate song. Thus, exposure to species-specific song with a conspecific male is sufficient to trigger learning. The sensory phase began after fledging, around 23 days posthatch, and the sensorimotor phase began around 50 days posthatch, when singing also began. Song crystallization occurred approximately 125 days posthatch. Costa's also appear to be statistical learners; they learn to sing the songs they hear most often. Hummingbird song ontogeny appears to be similar to song ontogeny in passerines, despite its convergent origin.

Response of Male Hawaii Elepaio Chasiempis sandwichensis to Conspecific Songs: A Small-Scale Playback Study

Las aves paseriformes aprenden sus cantos principalmente a traves de la transmision cultural. Sin embargo, la fragmentacion del habitat puede provocar una variacion cultural en el aprendizaje de cantos dando lugar a restricciones en la transmision de informacion cultural, incluyendo interacciones acusticas. En este estudio, nuestro objetivo es evaluar la respuesta individual a vocalizaciones de la misma especie dentro de dos poblaciones diferentes, asi como entre ambas poblaciones. Para ello, utilizamos reproducciones de cantos del monarca elepaio Chasiempis sandwichensis en un paisaje fragmentado que se encuentra en la ladera noreste del volcan Mauna loa (Isla de Hawai, EE.UU.). Evaluamos la respuesta de los machos de monarca elepaio a los cantos grabados en su misma poblacion, asi como en una poblacion diferente. Tambien comparamos vocalizaciones entre ambas poblaciones para evaluar diferenciacion acustica. Nuestros resultados indican divergencias comportamentales en la respuesta al canto de esta especie a pequena escala, asi como diferencias significativas en rasgos acusticos. Sin embargo, contrariamente a lo que se esperaba, los individuos de monarca elepaio de ambas poblaciones no variaron en su patron de respuesta a los cantos en funcion de su origen. Esto sugiere que la diferenciacion acustica puede no ser lo suficientemente fuerte como para dar lugar a una divergencia comportamental en la respuesta de los individuos de monarca elepaio, a pesar de la existencia de diferencias entre los rasgos acusticos de ambas poblaciones.

Song sharing in the pied bush chat (Saxicola caprata)

In most oscine passerine bird species, male song is composed of different song types of which some are shared with other males. Our aim for this study was to investigate whether song sharing occurs in the pied bush chat (a tropical species with multiple song types), and if so, whether neighbouring males share significantly more song types than non-neighbouring males and whether song sharing declines with increasing distance between males. A standard song sharing index was used to compare all song types of each male with all song types of all other males. Males had a mean repertoire of 22.8±4.4 song types ranging from 17 to 30 song types. Results revealed that neighbouring males shared significantly more song types than did non-neighbouring males. Nevertheless, no two males shared all song types in their repertoires. Furthermore, we observed a significant decline in the proportion of song repertoire shared with increasing distance between males. Results confirm the presence of song sharing in the pied bush chat, which may help neighbouring males to mediate social relationships.