Song Duration Research Articles

The evolution of birdsong on islands

Islands are simplified, isolated ecosystems, providing an ideal set-up to study evolution. Among several traits that are expected to change on islands, an interesting but poorly understood example concerns signals used in animal communication. Islands are typified by reduced species diversity, increased population density, and reduced mate competition, all of which could affect communication signals. We used birdsong to investigate whether there are systematic changes in communication signals on islands, by undertaking a broad comparison based on pairs of closely related island-mainland species across the globe. We studied song traits related to complexity (number of different syllables, frequency bandwidth), to vocal performance (syllable delivery rate, song duration), and also three particular song elements (rattles, buzzes, and trills) generally implicated in aggressive communication. We also investigated whether song complexity was related to the number of similar sympatric species. We found that island species were less likely to produce broadband and likely aggressive song elements (rattles and buzzes). By contrast, various aspects of song complexity and performance did not differ between island and mainland species. Species with fewer same-family sympatric species used wider frequency bandwidths, as predicted by the character release hypothesis, both on continents and on islands. Our study supports the hypothesis of a reduction in aggressive behavior on islands and suggests that discrimination against closely related species is an important factor influencing birdsong evolution.

Differential allocation in relation to mate song quality in the Bengalese finch

Postmating sexual selection plays an important part in the evolution of secondary sexual characters. Based on differential allocation theory that predicts biased reproductive investment of females depending on the attractiveness of mates, a number of previous studies have shown that egg production is related in various ways to ornamental sexual traits of males, but evidence for behavioural sexual traits is less abundant. In this study we examine such maternal effects in relation to birdsong. Because the Bengalese finch is a monomorphic songbird, courtship song serves a key role in mate choice. To take into account individual female differences in egg production performance, we sequentially paired naïve, captive, female Bengalese finches to two different males, and investigated if their reproductive investment (clutch size, egg mass and hatchling sex ratio) was related to the song traits of their mates. We found that clutch size and egg mass were highly repeatable within individual females while sex ratio was not. Despite the inflexibility of egg mass within each female, egg mass increased when females were mated to males with longer songs. In addition, we found a non-significant weak tendency toward male-biased sex ratio in relation to longer song duration of mates. Our findings suggest that females mated to better mates adjusted their reproductive investment by producing heavier eggs and possibly offspring of the more costly sex.

Humpback whale song hierarchical structure: Historical context and discussion of current classification issues

AbstractConsistent and well‐defined criteria for the classification and measurement of humpback whale song features are essential for robust comparisons between investigators. Song structure terminology has been well‐established and used by many authors, though at times inconsistently. This review discusses the development of the nomenclature describing humpback song and explores the potential significance of the often‐overlooked variation in song patterns. Within the hierarchical definition of humpback song, the most problematic issues arise from the inconsistent delineation of phrase types, and the use of the metric of song duration without regards to variability in thematic sequence. With regards to the former, a set of guidelines is suggested to facilitate consistent delineation of phrases. With regards to the latter, current research demonstrates that the “song duration” metric has resulted in the disregard of variability at this level, which is more widespread than traditionally reported. An exemplar case is used to highlight the problem inherent in defining and measuring song duration. Humpback song is evaluated within the framework of avian songbird research, and a shift in analysis paradigm is recommended, towards phrase‐based analyses in which sequences of phrases are treated as a salient feature of song pattern.

Striatal dopamine modulates song spectral but not temporal features through D1 receptors

The activity of midbrain dopaminergic neurons and their projection to the basal ganglia (BG) are thought to play a critical role in the acquisition of motor skills through reinforcement learning, as well as in the expression of learned motor behaviors. The precise role of BG dopamine (DA) in mediating and modulating motor performance and learning, however, remains unclear. In songbirds, a specialized portion of the BG is responsible for song learning and plasticity. Previously we found that DA acts on D1 receptors in Area X to modulate the BG output signal and thereby trigger changes in song variability. Here, we investigate the effect of D1 receptor blockade in the BG on song behavior in the zebra finch. We report that this manipulation abolishes social context-dependent changes in variability not only in harmonic stacks, but also in other types of syllables. However, song timing seems not to be modulated by this BG DA signal. Indeed, injections of a D1 antagonist in the BG altered neither song duration nor the change of song duration with social context. Finally, D1 receptor activation in the BG was not necessary for the modulation of other features of song, such as the number of introductory notes or motif repetitions. Together, our results suggest that activation of D1 receptors in the BG is necessary for the modulation of fine acoustic features of song with social context, while it is not involved in the regulation of song timing and structure at a larger time scale.

Time estimation: Musical training and emotional content of stimuli

In this study we investigated the effect of musical training and emotional content of stimuli on time estimation. Eighty students aged 12 to 15 years were equally divided into two main groups (musicians, non-musicians) based on whether they had formal music education or not. The participants took part in a music listening task and were asked to estimate the duration of a happy or a sad song. The results showed that: musical training affects temporal perception by allowing individuals to make more accurate estimations of time durations; the emotional content of the song affects time estimation, especially in the case of non-musicians; non-musicians overestimate the duration of sad songs while they underestimate the duration in the case of happy songs. These results emphasize the close relationship between time estimation, musical training, and emotion.

Melatonin affects the temporal pattern of vocal signatures in birds

In humans and other animals, melatonin is involved in the control of circadian biological rhythms. Here, we show that melatonin affects the temporal pattern of behavioral sequences in a noncircadian manner. The zebra finch (Taeniopygia guttata) song and the crow of the Japanese quail (Coturnix japonica) are courtship vocalizations composed of a stereotyped sequence of syllables. The zebra finch song is learned from conspecifics during infancy, whereas the Japanese quail crow develops normally without auditory input. We recorded and analyzed the complete vocal activity of adult birds of both species kept in social isolation for several weeks. In both species, we observed a shortening of signal duration following the transfer from a light-dark (LD) cycle to constant light (LL), a condition known to abolish melatonin production and to disrupt circadian rhythmicity. This effect was reversible because signal duration increased when the photoperiod was returned to the previous LD schedule. We then tested whether this effect was directly related to melatonin by removal of the pineal gland, which is the main production site of circulating melatonin. A shortening of the song duration was observed following pinealectomy in LD. Likewise, melatonin treatment induced changes in the temporal structure of the song. In a song learning experiment, young pinealectomized finches and young finches raised in LL failed to copy the temporal pattern of their tutor's song. Taken together, these results suggest that melatonin is involved in the control of motor timing of noncircadian behavioral sequences through an evolutionary conserved neuroendocrine pathway.

Undirected (Solitary) Birdsong in Female and Male Blue-Capped Cordon-Bleus (Uraeginthus cyanocephalus) and Its Endocrine Correlates

BackgroundBirdsong is a popular model system in research areas such as vocal communication, neuroethology or neuroendocrinology of behaviour. As most research has been conducted on species with male-only song production, the hormone-dependency of male song is well established. However, female singing and its mechanisms are poorly understood.Methodology/Principal FindingsWe characterised the song and its endocrine correlates of blue-capped cordon-bleus (Uraeginthus cyanocephalus), a species in which both sexes sing. Like other estrildids, they produce directed song during courtship and undirected (or solitary) song in isolation, i.e. when the mate is not visible or absent. We compare solitary song of blue-capped cordon-bleus to published descriptions of the song of its relative, the zebra finch (Taeniopygia guttata). Solitary song of cordon-bleus shared some overall song features with that of zebra finches but differed in spectro-temporal song features, sequential stereotypy and sequential organisation. The song of cordon-bleus was dimorphic with respect to the larger size of syllable repertoires, the higher song duration and the lower variability of pitch goodness (measuring the pureness of harmonic sounds) in males. However, in both sexes the overall plasma testosterone concentrations were low (ca. 300 pg/ml) and did not correlate with the sexually dimorphic song motor pattern. Despite such low concentrations, the increase in the rate of solitary song coincided with an increase in the level of testosterone. Furthermore, the latency to start singing after the separation from the mate was related to hormone levels.Conclusions/SignificanceOur findings suggest that the occurrence of solitary song but not its motor pattern might be under the control of testosterone in female and male cordon-bleus.

Does age matter in song bird vocal interactions? Results from interactive playback experiments.

The song of oscines provides an extensively studied model of age-dependent behaviour changes. Male and female receivers might use song characteristics to obtain information about the age of a signaller, which is often related to its quality. Whereas most of the age-dependent song changes have been studied in solo singing, the role of age in vocal interactions is less well understood. We addressed this issue in a playback study with common nightingales (Luscinia megarhynchos). Previous studies showed that male nightingales had smaller repertoires in their first year than older males and males adjusted their repertoire towards the most common songs in the breeding population. We now compared vocal interaction patterns in a playback study in 12 one year old and 12 older nightingales (cross-sectional approach). Five of these males were tested both in their first and second breeding season (longitudinal approach). Song duration and latency to respond did not differ between males of different ages in either approach. In the cross-sectional approach, one year old nightingales matched song types twice as often as did older birds. Similarly, in the longitudinal approach all except one bird reduced the number of song type matches in their second season. Individuals tended to overlap songs at higher rates in their second breeding season than in their first. The higher levels of song type matches in the first year and song overlapping by birds in their second year suggest that these are communicative strategies to establish relationships with competing males and/or choosy females.

Male–male vocal interactions in a territorial neotropical quail: which song characteristics predict a territorial male's response?

AbstractMales singing within their territories can change their song characteristics in order to interact with conspecifics; males may respond to territorial intrusions by vocalizing, approaching the intruder and/or displaying. I studied male–male interactions by quantifying vocal and behavioural responses of male spot-bellied bobwhites (Colinus leucopogon) toward playback of conspecific male songs. Male responses toward playback song depended on the quality of the territorial male's song relative to the playback stimulus. In this species males who sang songs with higher peak and low frequency, longer song duration, and lower song rate were less responsive to simulated territorial intrusions. Spot-bellied bobwhite males that sang in response to the playback increased the low frequencies of their songs relative to pre-playback song, a vocal behaviour related to dominance in males of other species. Males that approached the speaker sang longer songs, a characteristic associated with increased aggression or motivation to fight in other bird species. The results of this playback experiment suggest that male spot-bellied bobwhite song characteristics according to playback characteristics predict response to territorial intrusions and may, therefore, play an important role in male–male interactions.

Advertising vocalization of the clamorous reed warbler (Acrocephalus stentoreus, Sylviidae)

The advertising vocalization of the clamorous reed warbler, one of the least studied representatives of the genus in the Palearctic, has been analyzed. In this species, advertising vocalization consists of compact acoustic constructs (songs) separated by pauses. The duration of songs (median 3.6 s) and pauses (median 2.9 s) varies only slightly. Each song consists of three to four different or identical syllables. Syllables (stereotyped acoustic constructs) consist of two to four notes. Each male has from 5 to 25 syllables in his repertoire. A sharp contrast between low-frequency and high-frequency notes and strict sequence of these notes in syllables (low-frequency notes come first, then follow high-frequency notes) are characteristic of this song. All types of syllables in the song of a given male can be divided into two groups: initiator syllables and other syllables. Initiator syllables most often occur at the beginning, while others occur in the middle or at the end of the song. Stable links between syllables have been revealed: the majority of them occur in the song together with certain syllables (one or two) of other types. The whole range of songs of each individual can be divided into several classes. A certain type of initiator syllable and a certain set of subsequent syllables are characteristic of each class. However, the variability of songs within each class is quite high. Modes of immediate and eventual variety alternate in the sequence of songs from different classes. Thus, 47.4% of songs are followed by a song from the same class (eventual variety), while 52.6% of songs are followed by a song from a different class (immediate variety). The advertising vocalization of the clamorous reed warbler is compared with that of other representatives of the genus Acrocephalus.

Effects of Breeding Stage and Behavioral Context on Singing Behavior of Male Indigo Buntings

Abstract We studied the effects of breeding stage and behavioral context on the singing behavior of male Indigo Buntings (Passerina cyanea; n = 15) during the 2004 breeding season in Madison County, Kentucky, USA, to better understand how males with a single-song repertoire vary the characteristics of their song to convey different information. Playback experiments were conducted in 2005 in territories of focal males (n = 14) to further examine the possible effect of male-male interactions on singing behavior. We analyzed 10,919 songs of 15 male Indigo Buntings with songs consisting of a series of figures that were usually paired (i.e., phrases). Mean song duration was 2.30 ± 0.13 (SE) sec (range = 1.44–3.40 sec) with males varying song duration by varying the number of figures and phrases in each song. Singing rates varied significantly (P < 0.0001) among breeding stages and were highest prior to pairing, suggesting singing has a role in mate attraction. Singing rates also differed (P = 0.013) du...

Songs of Darwin's finches diverge when a new species enters the community

Bird species sing different songs and as a result rarely breed with each other. Species are not static but can shift in acoustic and morphological space, yet maintain their distinctiveness. Investigating such a situation in a community of Darwin's finches sheds light on the origin and maintenance of premating barriers between species. Explanations for songs divergence generally invoke morphological changes to the sound-producing apparatus, environmental changes influencing transmitting properties of song, avoidance of acoustical interference with other species, and random processes including copying errors. We investigated changes in songs of Geospiza fortis (medium ground finch) and Geospiza scandens (cactus ground finch) from 1978 to 2010 on Daphne Major Island, Galápagos. The habitat did not change significantly; however, the finch community changed. The socially aggressive congener Geospiza magnirostris (large ground finch), singing in the same frequency band (2–4 kHz), colonized Daphne in 1983 and increased in numbers. Temporal features of the songs of G. fortis and G. scandens , especially trill rate and song duration, diverged from G. magnirostris songs as it became increasingly common. Changes in song were not a passive consequence of a change in beak morphology. Instead they arose as a bias during song imprinting and production. Sons of both G. fortis and G. scandens sang faster songs than their respective fathers and thereby differed more from G. magnirostris in their songs than did their fathers. Divergence from an aversive or confusing stimulus during learning illustrates a “peak shift” that may be a common feature of song evolution and speciation.

Differential Influence of Frequency, Timing, and Intensity Cues in a Complex Acoustic Categorization Task

Songbirds, which, like humans, learn complex vocalizations, provide an excellent model for the study of acoustic pattern recognition. Here we examined the role of three basic acoustic parameters in an ethologically relevant categorization task. Female zebra finches were first trained to classify songs as belonging to one of two males and then asked whether they could generalize this knowledge to songs systematically altered with respect to frequency, timing, or intensity. Birds' performance on song categorization fell off rapidly when songs were altered in frequency or intensity, but they generalized well to songs that were changed in duration by >25%. Birds were not deaf to timing changes, however; they detected these tempo alterations when asked to discriminate between the same song played back at two different speeds. In addition, when birds were retrained with songs at many intensities, they could correctly categorize songs over a wide range of volumes. Thus although they can detect all these cues, birds attend less to tempo than to frequency or intensity cues during song categorization. These results are unexpected for several reasons: zebra finches normally encounter a wide range of song volumes but most failed to generalize across volumes in this task; males produce only slight variations in tempo, but females generalized widely over changes in song duration; and all three acoustic parameters are critical for auditory neurons. Thus behavioral data place surprising constraints on the relationship between previous experience, behavioral task, neural responses, and perception. We discuss implications for models of auditory pattern recognition.

Female response to song reflects male developmental history in swamp sparrows

One explanation for why female songbirds attend to male song is that the quality of a male's song is associated with the quality of his developmental history. We tested this hypothesis by playing back to female swamp sparrows (Melospiza georgiana) songs recorded from males of either inferior or superior developmental histories, as assessed by their rates of mass gain during the first 18 days post-hatching. Females showed significantly higher levels of courtship display in response to songs of males with superior growth than to songs of males with inferior growth. Out of nine song traits measured, only song duration correlated with variation in female response; duration was also the only trait that differed significantly in univariate comparisons between the superior growth songs and the inferior growth songs. In a multivariate analysis, however, inferior growth songs were best discriminated from superior growth songs by combining three song traits: trill rate, stereotypy, and the number of notes per syllable. We suggest that early developmental stress degrades song in many small ways, and that it is the cumulative effect of the resulting deficits that explains lower female response.

Age-related changes of song traits in female European Starlings (Sturnus vulgaris)

AbstractIn contrast to male bird song, female song complexity, learning and expression have received much less attention. Female European starlings can produce song of a comparable complexity as males and are also capable of adult vocal learning. Here we recorded song during 3 successive years and investigated variation in song traits (song complexity, song duration and song versatility) in relation to age in captive adult female starlings. We looked at whether individual song traits differ among different age classes (cross-sectional analyses) and whether they change over successive years (longitudinal analyses). Further we studied the repertoire turnover throughout the years, female song sharing in the first year of recording and whether different song traits consistently vary among females across the years. Overall, both cross-sectional and longitudinal analyses showed that repertoire size significantly declined with female age, suggesting that some constraints exist in adult females to maintain large repertoires. Song duration and song versatility appeared to be unrelated to age. Female starlings intensely modified their repertoire across the years by adding new/deleting old phrase types, suggesting a high plasticity as reported in males. Females showed a high variation (between 14% and 83%) in sharing their repertoire, with older females having higher song sharing rates. The individual differences in song complexity and performance were repeatable across the years, which may suggest that song in female starlings is a potential quality indicator trait.

Aviary Experience Has No Effect on Predisposition of Female Common Canaries (Serinus canaria) for Longer Sexy Phrases

ABSTRACT. We tested female Common Canaries' (Serinus canaria) preferences for “sexy phrases” of different durations. Two groups were used: (1) females raised in acoustic isolation and (2) females raised in “normal” acoustic conditions. We presented sexy phrases to both groups and counted their copulation-solicitation displays to determine their preference for the length of these stimuli. Females of both groups gave more copulation-solicitation displays in response to the longest sexy phrases presented. Our results indicate that the duration of sexy phrases is an important acoustic cue for female Common Canaries, as is total song duration in many species; this preference can be explained by theories of sexual selection. Moreover, responses of both experienced and inexperienced females are similar, which indicates that experience does not influence the females' preference for long sexy phrases. These preferences could come from predispositions, as is the case for many acoustic parameters of sexy phrases.

Developmental stress affects song learning but not song complexity and vocal amplitude in zebra finches

Several recent studies have tested the hypothesis that song quality in adult birds may reflect early developmental conditions, specifically nutritional stress during the nestling period. Whilst all of these earlier studies found apparent links between early nutritional stress and song quality, their results disagree as to which aspects of song learning or production were affected. In this study, we attempted to reconcile these apparently inconsistent results. Our study also provides the first assessment of song amplitude in relation to early developmental stress and as a potential cue to male quality. We used an experimental manipulation in which the seeds on which the birds were reared were mixed with husks, making them more difficult for the parents to obtain. Compared with controls, such chicks were lighter at fledging; they were thereafter placed on a normal diet and had caught up by 100 days. We show that nutritional stress during the first 30 days of life reduced the birds’ accuracy of song syntax learning, resulting in poorer copies of tutor songs. Our experimental manipulations did not lead to significant changes in song amplitude, song duration or repertoire size. Thus, individual differences observed in song performance features probably reflect differences in current condition or motivation rather than past condition.

Universal Features in the Singing of Birds Uncovered by Comparative Research

Aside from some exceptions, songbird species differ in the structure of their singing and usually also in the size and performance mode their song repertoires. In the past, most studies concentrated on the species specific differences of singing, and thereby contributed to a better understanding of their diversity. In our approach, however, we focussed on the opposite perspective; i.e. we investigated whether and how far songbirds share structural song properties. To have a solid data base we focussed on four species of thrushes which were famous for their large vocal repertoires. The two Asian bird species were Oriental Magpie Robins (Copsychus saularis) and Shama Thrushes (Copsychus malabaricus), the two European species the Common Nightingale (Luscinia megarhynchos) and the Thrush Nightingale (Luscinia luscinia). The latter were incorporated into a sample 40 other European songbird species (Table 1) serving as a framework for our comparative approach (Figure 2, 4). Besides well-known differences among species, our analyses of song material yielded some remarkably similar relationships between structural and functional song properties, which often were shared even by unrelated species. In particular measures of song durations were usually related to song application during vocal interaction. And, individual variation of song duration was mainly a result of differences in syllable repetition within trilled song sections. Although some of these findings were predicted already by former studies (see Todt, 2004), their essentials can be based now on profound data sets of detailed measurement.Keywords: European Thrushes, Asian Thrushes, Copsychus saularis, C. malabaricus, song structure, signal lengths.doi: 10.3126/on.v6i1.1648Our Nature (2008)6:1-14

Long-term effects of early parasite exposure on song duration and singing strategy in great tits

Song is a sexually selected trait in many bird species and has been suggested to function as a signal of a male's health and parasite resistance. Here we present an experimental field study on the long-term effects of parasite exposure early in life on adult bird song. We exposed nestling great tits (Parus major) to ectoparasitic hen fleas (Ceratophyllus gallinae) and on their recruitment into the local breeding population assessed the response to a playback of a challenging male in their breeding territory. We show, to our knowledge for the first time in a wild bird population, that parasite exposure early in life affects bird song: song duration of males that were exposed to parasites early in life was reduced by 32% compared with males that grew up in a flea-free environment. Early parasite exposure also significantly reduced the degree of song overlap with the playback, which has been shown to correlate with social status. There was no effect of early parasite exposure on the number of different song types sung or on the latency until the males started the vocal response to the playback. These results suggest that mates or rivals can use song duration and song overlap as proxies for an individual's exposure to parasites early in life. It thereby highlights both the importance of parasites in maintaining honesty of sexually selected traits and the costs of parasitism in terms of reduced attractiveness and competitiveness.

Syntactical complexity of songs in the Black-browed Reed Warbler Acrocephalus bistrigiceps

Abstract The transition patterns of syllables (syntactical complexity) in songs of the Black-browed Reed Warbler (Acrocephalus bistrigiceps) were more complex than previously measured in the domestic bird, the Bengalese Finch (Lonchura striata var. domestica). Syntactical complexity was correlated with song duration (song length), which implies that these song characteristics have a similar function, probably in sexual selection. Syntactical complexity was not correlated with repertoire size (the number of syllable types), which is another presumable sexually selected trait but may not be important in this species, as previously suggested. Future studies on birdsongs should focus on not only repertoire size but also syntactical complexity.