Multiple Song Types Research Articles

How long are the vocal sequences a passerine bird can memorize? Common song sequences of Radde’s warbler males (Phylloscopus schwarzi) (Passeriformes, Aves)

In most passerine species, an individual bird sings multiple song types to be combined into non-random song sequences. Because of this non-randomness, stereotype sequences of several or even dozens of song types appear in the vocalization of some species. Passerine birds acquire songs through some learning process while imitating other individuals. Song sharing is well known in songbirds and is a consequence of the song learning. Apparently, above the song type level, transitions between song types may be also shared. However, we still do not know exactly, how long are those song sequencies a bird can memorize? We analyze song sequence sharing in Radde’s warbler. Each song of this species consists of a dozen of short notes and lasts 1 s. In many males, the identity of the next song type in a sequence can be predicted on the basis of the previous song type (linear syntax). We found that males can share (i.e. memorize) song sequences from no more than 5 song types. Individual repertoires included up to 40 song types. Therefore, the ability of memorizing song sequences are rather limited in Radde’s warbler, as shared song sequences were rather short in comparison with the total size of the repertoire.

Song theme sharing in the Grey-crowned Warbler Phylloscopus tephrocephalus

ABSTRACT In many songbird species, individuals sing multiple song types, some of which are shared between neighbours. Individuals may also share transitions between different song types, which leads to sharing sequencies of several (usually few) song types. Song themes, i.e. groups of song types that are consistently delivered in close succession, were identified in song sequences of several bird species. Detailed data on song theme sharing are still lacking. Here, we examined patterns of repertoire sharing in the Grey-crowned Warbler Phylloscopus tephrocephalus. Males of this species had repertoires of 29–42 song types that were divided into shorter song themes of up to 10–15 song types each. Each of the 13 studied males shared 81.6–100% of his repertoire as well as several song themes with other males. These themes recombined in different ways leading to the fact that exact song sequencing varied between individuals. That is why males shared much less transition types than song types in our study. Therefore, the analysis of song theme sharing may provide more careful description of sharing above the level of song type than the analysis of song sequence sharing alone.

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.

Network analysis reveals underlying syntactic features in a vocally learnt mammalian display, humpback whale song.

Vocal communication systems have a set of rules that govern the arrangement of acoustic signals, broadly defined as 'syntax'. However, there is a limited understanding of potentially shared or analogous rules across vocal displays in different taxa. Recent work on songbirds has investigated syntax using network-based modelling. This technique quantifies features such as connectivity (adjacent signals in a sequence) and recurring patterns. Here, we apply network-based modelling to the complex, hierarchically structured songs of humpback whales (Megaptera novaeangliae) from east Australia. Given the song's annual evolving pattern and the cultural conformity of males within a population, network modelling captured the patterns of multiple song types over 13 consecutive years. Song arrangements in each year displayed clear 'small-world' network structure, characterized by clusters of highly connected sounds. Transitions between these connected sounds further suggested a combination of both structural stability and variability. Small-world network structure within humpback songs may facilitate the characteristic and persistent vocal learning observed. Similar small-world structures and transition patterns are found in several birdsong displays, indicating common syntactic patterns among vocal learning in multiple taxa. Understanding the syntactic rules governing vocal displays in multiple, independently evolving lineages may indicate what rules or structural features are important to the evolution of complex communication, including human language.

Neural Evolution of Context-Dependent Fly Song

It is unclear where in the nervous system evolutionary changes tend to occur. To localize the source of neural evolution that has generated divergent behaviors, we developed a new approach to label and functionally manipulate homologous neurons across Drosophila species. We examined homologous descending neurons that drive courtship song in two species that sing divergent song types and localized relevant evolutionary changes in circuit function downstream of the intrinsic physiology of these descending neurons. This evolutionary change causes different species to produce divergent motor patterns in similar social contexts. Artificial stimulation of these descending neurons drives multiple song types, suggesting that multifunctional properties of song circuits may facilitate rapid evolution of song types.

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.

Assessing the similarity of song-type transitions among birds: evidence for interspecies variation

In many species of songbird, individuals sing multiple song types, some of which are shared with their neighbours. Individuals may also share syntactical rules that govern the transitions between different song types, but few studies have attempted to study this kind of sharing. Progress has been inhibited by a lack of statistical tools to compare song-type transitions among individuals. We present a straightforward method for comparing song transitions based on Markov transition matrices. The method calculates the number of mutually preferred song-type-to-different-song-type transitions found in the song sequences of two birds, then assesses whether that number is significantly greater than would be expected if the two birds ordered their songs independently of one another. We applied this method to song sequences from five songbird species. All pairwise comparisons among male Cassin's vireos, Vireo cassinii, showed significant similarity in song transitions, as did a minority of comparisons among Adelaide's warblers, Setophaga adelaidae, and one pair of marsh wrens, Cistothorus palustris. In contrast, dyads of rock wrens, Salpinctes obsoletus, and rufous-and-white wrens, Thryophilus rufalbus, did not share song-type transitions at levels exceeding chance. Interterritory distance was not significantly related to our measure of song transition similarity in any of our study species. These results provide evidence that interindividual similarity in song-type transitions is a trait that varies considerably among species. We discuss the potential drivers of similarity in song transitions, but note that assessing its evolutionary breadth will require a larger sample of species. The application of our method to additional species will provide a more comprehensive understanding of signal use and vocal interaction in songbirds.

Use of Two Song Types by Townsend's Warblers (Setophaga townsendi) in Migration

ABSTRACT.— The use of song by wood-warblers (Parulidae) with multiple song types has received little attention during migration. On the breeding area, the two song types serve to attract mates and defend territory, but the function(s) during migration, if any, are unclear. I studied the singing of Townsend's Warblers (Setophaga townsendi) during spring migration through southern Oregon and northern California. Males preferentially used Type II songs (79%) whether alone or in flocks of up to ∼20 individuals. Type I songs of wood-warblers tend to be acquired early in the hatch year while Type II songs appear to be subject to modification over an extended period of time. The preference for Type II songs in migration may reflect an important period in the development of Type II song. More than one dialect of Type I song was recorded within flocks indicating that flocks were composed of individuals from different breeding populations. Type II songs are recognizably similar in breeding populations from central ...

Playback experiments for Thryothorus ludovicianus in urban backyard experiments

Acoustic playback experiments were performed from June 2014 to April 2015 for Thryothorus ludovicianus (Carolina Wren) in a backyard environment in Austin, Texas. Acoustic recordings were made for pre-playback, playback, and post-playback periods for multiple song types. The songs were obtained from recordings made in the backyard and surrounding neighborhood. Recordings of both the playback and acoustic responses of the bird subjects are made in coincidence with visual observations of the bird’s behavior. Bird behavior is quantified in terms of the statistics of closest distance of approach, latency to approach, latency to sing, number of post-playback songs, number of flybys, percent of male-female duets, temporal correlation of individual song phrases, and number of singing competitions with neighboring subjects. Statistics of the properties of the measured spectrograms and spatial correlation properties for experiments are presented, and attempts are made to interpret the observed behavior and acoustical responses of the birds in the form of communication and territorial defense with the bird’s ability to estimate distance using the degradation (transmission loss and reverberation) of the playback calls. It was also observed that Thryothorus ludovicianus will respond to playback calls of Cardinalis cardinalis (Northern Cardinal) and this interaction between bird species is examined.

Vocal Distinctiveness and Information Coding in a Suboscine with Multiple Song Types: Eastern Wood-Pewee

Abstract We tested individual distinctiveness, a prerequisite for individual recognition, in the songs of the suboscine Eastern Wood-Pewee (Contopus virens). Male Eastern Wood-Pewees produce two main song types: ‘pee-ah-wee’ and ‘wee-ooo’ songs. All song variables for both song types, including temporal and frequency variables, showed greater between than within individual variation. Thus, both song types contained the potential to code information on individual identity and quality. Pee-ah-wee songs were more variable than wee-ooo songs, and pee-ah-wee frequency variable measures were the most variable. We correctly assigned 97.5% of pee-ah-wee songs and 95.0% of wee-ooo songs to the bird of origin–demonstrating individual distinctiveness in both main song types.

Spatial and age-related variation in use of locally common song elements in dawn singing of song sparrows Melospiza melodia: old males sing the hits

In many songbirds, individuals have repertoires of multiple song types, some of which may be shared with others in the local area. Hypotheses about the evolution of song repertoires differ as to whether selection acts primarily on repertoire size itself or the ability to match songs of neighbours. We used a 16-channel acoustic location system to record neighbourhoods of song sparrows (Melospiza melodia melodia) during the dawn chorus. We asked whether males sing all songs with similar frequency as predicted by the Repertoire Size Hypothesis, whether males preferentially sing highly shared songs as predicted by the General Sharing Hypothesis, or whether use of highly shared songs is associated with phenotype as predicted by the Conditional Sharing Hypothesis. Contrary to the Repertoire Size Hypothesis, most males did not sing all songs equally often. Contrary to the General Sharing Hypothesis, we found no general tendency to overproduce highly shared songs. The degree to which males overproduced highly shared songs was repeatable across days, indicating consistent individual differences, and varied across neighbourhoods. Moreover, and consistent with the Conditional Sharing Hypothesis, older males were more likely to overproduce highly shared songs. If highly shared song is a conventional signal of aggression, with the threat of receiver retaliation maintaining honesty, older males may be more willing or able to risk conflict. Alternatively, males may learn which songs are effective signals for an area. Finally, age-related variation in vocal performance may shape the adaptive value of highly shared song.

Dynamic Horizontal Cultural Transmission of Humpback Whale Song at the Ocean Basin Scale

Cultural transmission, the social learning of information or behaviors from conspecifics, is believed to occur in a number of groups of animals, including primates, cetaceans, and birds. Cultural traits can be passed vertically (from parents to offspring), obliquely (from the previous generation via a nonparent model to younger individuals), or horizontally (between unrelated individuals from similar age classes or within generations). Male humpback whales (Megaptera novaeangliae) have a highly stereotyped, repetitive, and progressively evolving vocal sexual display or "song" that functions in sexual selection (through mate attraction and/or male social sorting). All males within a population conform to the current version of the display (song type), and similarities may exist among the songs of populations within an ocean basin. Here we present a striking pattern of horizontal transmission: multiple song types spread rapidly and repeatedly in a unidirectional manner, like cultural ripples, eastward through the populations in the western and central South Pacific over an 11-year period. This is the first documentation of a repeated, dynamic cultural change occurring across multiple populations at such a large geographic scale.

Bowhead whale (Balaena mysticetus) songs in the Chukchi Sea between October 2007 and May 2008

This paper reports on the acoustic detection of bowhead whale (Balaena mysticetus) songs from the Bering-Chukchi-Beaufort stock, including the first recordings of songs in the fall and early winter. Bowhead whale songs were detected almost continuously in the Chukchi Sea between October 30, 2007 and January 1, 2008 and twice from April 16 to May 5, 2008 during a long-term deployment of five acoustic recorders moored off Point Lay and Wainwright, AK, between October 21, 2007 and August 3, 2008. Two complex and four simple songs were detected. The complex songs consisted of highly stereotyped sequences of four units. The simple songs were primarily made of sequences of two to three moan types whose repetition patterns were constant over short periods but more variable over time. Multiple song types were recorded simultaneously and there is evidence of synchronized song variation over time. The implications of the spatiotemporal distribution of song detection with respect to the migratory and mating behavior of western Arctic bowheads are discussed.

Vocal communication in a songbird with a novel song repertoire

Why do individuals in many songbird species sing multiple song types? Previous studies have often described the current utility of possessing a vocal signal repertoire, but this may not explain why repertoires evolve. We looked for repertoire function in black-capped chickadee (Poecile atricapillus) populations with a song type repertoire that is probably derived from the single song type found in most populations across the species' geographic range. Through observations of dawn singing, and natural and simulated territorial countersinging interactions, we tested several hypotheses on how a repertoire might facilitate improved vocal communication. We failed to find significant evidence supporting an adaptive origin for song type repertoires. Although we found that naturally countersinging males matched song type approximately twice as often as expected by chance, matching was not associated with conflict escalation in either natural or simulated contests and, therefore, the exact function of song type matching in these birds remains unclear. In addition, we found that novel song types frequently appear in small isolated populations, which suggests that a repertoire might evolve simply as the nonadaptive result of imperfect song-learning combined with geographic isolation.

Acoustic identification of individual Rufous Bristlebirds, a threatened species with complex song repertoires

Rufous Bristlebirds (Dasyornis broadbenti), possess song repertoires of between 12 and 30 different song-types, only a proportion of which are shared between different individuals. As a result, the comparison of songs among individuals is complicated by the use of multiple song-types. Using both discriminant function analysis (DFA) and spectrographic cross-correlation analysis (SPCC), those song-types that were shared among individuals demonstrated high levels of vocal individuality. DFA correctly classified an average of 98.3 ± 1.2% of male songs, whereas SPCC correctly classified an average of 87.4 ± 2.8% of songs. However, common song features among song-types showed limited value for individual identification. The information provided by the SPCC analyses was then used to discriminate among individuals over a distance of 7.8 km, the results of which supported those of previous studies with regard to the sedentary nature of Bristlebirds. Although the results of the present study show promise, the issue of song comparisons among multiple song-types remains a significant challenge for the development of acoustic identification systems for this species.

Auditory responses in the HVC of anesthetized starlings

The present study, using a systematic recording method that we recently developed, describes the behavior of the neurons of the vocal control nucleus HVC in response to a variety of acoustic stimuli in a songbird species with multiple song types, the European starling. Most neurons did not respond to any of the stimuli that were presented, and those neurons that did respond responded to a different number of stimuli and showed distinct response features. The latter were thus classified into 3 categories, according to the number of stimuli to which they responded. Although only intracellular data could unambiguously determine to which population the neurons we recorded belonged, these 3 categories might correspond to the 3 populations of neurons that have been previously described in the HVC. Interestingly, responsive neurons of the 3 categories appeared to mainly respond to stimuli that were not the bird's own song. However, most of the stimuli to which the HVC neurons responded correspond to sounds that are important in the everyday social life of the starlings. We thus discuss our results in relation to the social life of these birds, to possible species differences in the processing of communicative signals, and to methodological issues.

New insights into the auditory processing of communicative signals in the HVC of awake songbirds

In the present study, using a systematic recording method and a variety of stimuli, we determined the proportion of responsive sites and their response features in the vocal control nucleus HVC of awake-restrained starlings, a species with multiple song types. Responsive sites were classified into three groups, according to the number of stimuli to which they responded. Sites in the three groups showed responses to individual-specific songs, with sites in the group that showed responses to only one stimulus responding mostly to a bird’s own song. In comparison, very few sites exhibited responses to universal species-specific songs and to artificial nonspecific sounds. By contrast, data obtained in the same birds under urethane anesthesia show that, although the total proportion of responsive sites was similar, numerous responses to a universal species-specific song and to an artificial nonspecific pure tone could be observed.

Partial song matching in an eastern population of song sparrows, Melospiza melodia

One hypothesis for the function of vocal repertoires in songbirds is that singing multiple song types facilitates song matching, a behaviour in which one male replies to a rival's song with a song of the same type. In eastern populations of song sparrows, low levels of whole song sharing restrict opportunities for matching of entire song types. A male in this population might still match a neighbour by replying with a partially shared song (i.e. a song that contains one or more phrases in common with the neighbour's song). We tested for partial matching in a Pennsylvania population using playback of three categories of song: self song (allowing a full match), stranger song (a control allowing no match) and hybrid self/stranger song (allowing a partial match). We also tested the hypothesis that matching is a directed signal of aggressive intentions by comparing subjects' approach distances between trials in which they did and did not match. Males in our study matched in response to both self song (21 of 39 trials) and hybrid song (23 of 40 trials) at levels significantly greater than expected based on control trials (5 of 40 trials). Males that performed a partial match to a hybrid song approached the speaker more closely than males that did not match, consistent with the hypothesis that partial matching is a directed signal of aggression. Self song matching did not predict approach as successfully.

Auditory representation of the vocal repertoire in a songbird with multiple song types.

Neural mechanisms for representing complex communication sounds must solve the problem of encoding multiple and potentially overlapping signals. Birdsong provides an excellent model for such processing, in that many songbird species produce multiple song types. Although auditory song representations in single song type species have been studied, how song is represented in the brains of species that sing multiple song types remains unknown. Here we examine song type representations in swamp sparrows (Melospiza georgiana), a multiple song type species, by making in vivo intracellular recordings from the telencephalic nucleus HVc, the major auditory-vocal interface in the songbird brain. These recordings show that single HVc relay neurons often generate action potentials to playback of only a single song type, even though synaptic inputs on these cells can be activated by playback of other song types in the bird's repertoire and songs of other birds. These subthreshold response patterns suggest that the song evoked action potential discharge of a single relay neuron is more selective than its presynaptic network. One component of this presynaptic network is likely to be in HVc, because multiple recordings from single birds show that different relay neurons can respond best to different song types, whereas single interneurons can generate action potentials to all song types in the bird's repertoire. These results show that single HVc neurons can generate song type-specific action potential responses, a feature that may facilitate the selective auditory encoding of multiple learned vocalizations in a single brain area.

Re-expression of songs deleted during vocal development in white-crowned sparrows, Zonotrichia leucophrys

White-crowned sparrows learn and produce multiple song types as juveniles, but most individuals stop singing all except one by the end of the first singing season. This single song type is generally maintained throughout adulthood. We demonstrate that, at the start of the second and subsequent singing seasons, this species can recall songs that had been deleted during the first singing season. The re-expression of song occurred in both the oriantha and the gambelii subspecies. Although all our males recrystallized the original song in the second year, our results indicate a mechanism for seasonal song change without new song memorization. The traditional dichotomy of closed-ended versus open-ended learning is inadequate for birds that learn early in life but can change their song output seasonally. We suggest that species can exhibit a closed sensitive period for song memorization and first production, with the ability to recall deleted songs later in life. This type of learning, selective attrition followed by subsequent re-expression, may be used by some species currently considered open-ended learners.