Variation In Bird Song Research Articles

Vocal Repertoire of Chimango Caracaras in Rural and Urban Habitats

ABSTRACT Acoustic communication, such as bird song, is vital in animal ecology, facilitating reproduction, feeding, defense, and more. Variation in bird song may result from adaptation to environmental features such as anthropogenic noise. The vocal repertoire of raptors is essentially unstudied, particularly in urban environments. The aim of this work was to describe and quantify the acoustic repertoire of Chimango Caracaras (Milvago chimango) in rural and urban areas in La Pampa Province, Argentina. I recorded 26 1-min sound samples at each of four breeding colonies (one rural and three urban) during the austral reproductive season of 2021–2022. I recorded 241 vocalizations corresponding to nine clearly distinct call types. Two types of calls made up 50.6% and 19.5% of the vocalizations and seven others made up <10.0% each. Three call types had trills (fast repetitive notes). Average percentage of call types differed significantly between the two habitats (P < 0.01), with more trills produced in rural habitats. Average calling rate was 6.6 ± 5.1 calls/min at rural colonies and 10.7 ± 10.7 at urban colonies. The number of different call types produced was 2.1 ± 1.6 types/min at rural colonies and 2.7 ± 1.8 at urban colonies. The greater calling rate of Chimango Caracaras in urban areas may represent an attempt to improve signal effectiveness among the anthropogenic acoustic clutter.

Microgeographical variation in birdsong: Savannah sparrows exhibit microdialects in an island population

Social communication often involves vocal learning, whereby young animals learn their vocalizations early in life by imitating the sounds of adults. In animals that learn their vocalizations, it is common to find patterns of geographical variation known as ‘vocal dialects’, acoustic features shared within a cluster of animals that differ from the vocalizations of animals in nearby clusters. Dialects may form when animals learn their vocalizations early in life and then disperse short distances, or when they modify their vocalizations to match local vocal patterns after dispersal. Dialects are typically studied at a regional or continental scale, but they may also persist at smaller scales in so-called ‘microgeographical song dialects’ or ‘microdialects’. Microdialects have received little research attention. In this study, we investigate microdialects and dispersal distance in song-learning Savannah sparrows, Passerculus sandwichensis, through a 4-year study of birds living on three islands in the Bay of Fundy, Canada. Our analyses yield evidence of microgeographical variation: birds showed higher acoustic similarity to their neighbours than to faraway individuals in the same population. When we classified songs on the basis of their highly variable middle sections, we found that particular song types formed spatial clusters of similar-sounding individuals. Therefore, acoustic variation in Savannah sparrow song appears to show dialects across small geographical distances. In an analysis of dispersal from natal sites to breeding sites, we found a median distance of 189 m, consistent with previous findings. Our results suggest that limited dispersal distances, combined with the social processes of vocal learning (overproduction and selective attrition), likely contribute to the presence of microdialects.

Song variation between sexes and among subspecies of New Zealand Fantail (Rhipidura fuliginosa)

ABSTRACT Variation in bird song occurs at many levels, including between sexes and among geographic regions. Variation can be due to differences in function, habitat, selection or drift. Quantifying when and where such differences occur provides insight into which of these drivers is most likely. Here we examine song variation, (a) between sexes and (b) among the three geographically isolated subspecies, of the New Zealand Fantail (Rhipidura fuliginosa), a monomorphic passerine native to New Zealand. We measured twelve temporal and frequency parameters from recorded songs based on buzz notes. Only maximum frequency in one of the three phrases showed a significant sex difference, although there were suggestions of other sex differences in some element-level parameters. Song characteristics differed notably among subspecies; North Island Fantails typically produced shorter songs, comprised shorter elements at higher frequencies and faster element rates, while the most isolated birds (Chatham Island population), sang longer, slower songs. South Island birds were intermediate and more variable. The similarity of male and female songs suggests song is used by both sexes for similar purposes, while selection pressures associated with different habitats or cultural drift may be responsible for the song differences observed among sub-species. Further research analysing vocalisations of both sexes across a broader geographical range is required to further our understanding of female song function and patterns of geographic variation.

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.

Geographic Variation in Yellow Bunting Songs

In Japan, geographic variation in bird song is known only on small peripheral islands with isolated populations, and has not been reported in any species on the main islands of Japan, probably due to the close proximity of the populations on the relatively small main islands. On Honshu, one of the four main islands of Japan, the Yellow Bunting Emberiza sulphurata breeds in restricted habitats (i.e. wet grasslands with forest edge, or wet grasslands with sparse forest). This may facilitate the isolation of its populations and may have led to geographic variation in its songs. We investigated the acoustic characteristics of the songs of Yellow Buntings from four populations in central Honshu and found differences among the populations. For example, males at Nagaoka sang short songs with highly frequency-modulated notes, whereas males at Fuji sang long songs with poorly modulated notes. This study demonstrated geographic variation in bird songs on a small scale in mainland Japan. As songs are formed through cultural learning, local songs can arise in loose isolation or for short periods.

Microgeographic call variation in a non-learning species, the Corncrake (Crex crex)

Microgeographic variation in bird song has been studied in many species. However, it remains to be more fully described in birds that do not learn song and that thus have largely innate vocalisations. In this study, we focused on microgeographic variation in the territorial calls of one such non-learning species, the Corncrake (Crex crex). We examined the temporal and spectral characteristics of male Corncrake calls recorded in five separate populations in Poland. We found significant but weak relationships between some of the call characteristics and between-caller distances in four populations. The patterns observed were inconsistent. For some call characteristics, similarity decreased as distance between callers increased, while the opposite was true for other characteristics. Moreover, the same call characteristics showed opposite patterns in different populations or even within the same population but in different years. These findings suggest that the specific spatial distribution of the different quality habitats in which populations are located may have a crucial influence on microgeographic variation in calls. Alternatively, in non-learning species, various levels of microgeographic variation in calls might arise independently as a consequence of (1) social interactions among males, during which birds modify some parameters of their inherited call; or (2) territory occupancy patterns that minimize or maximize call similarity among neighbours.

Non‐Salient Geographic Variation in Birdsong in a Species That Learns by Improvisation

AbstractGeographic variation in birdsong and differential responses of territorial males to local and non‐local song variants have been documented in a number of songbird species in which males learn their songs through imitation. Here, we investigated geographic song variation and responses to local and non‐local song in the grasshopper sparrow (Ammodramus savannarum), a species in which males develop song by improvisation rather than imitation, as a first step toward understanding how the extent and salience of geographic song variation is related to the mode of song development. To describe the geographic variation in song, we compared songs from populations in eastern Maryland and central Ohio, USA, using multiple acoustic analysis techniques. We then conducted a playback experiment in Maryland using local and non‐local (Ohio) songs to test how territorial males responded to this geographic variation. We found acoustic differences between songs from the two sites. However, males responded similarly to playback of these songs, suggesting that this geographic variation is not behaviorally salient in a territorial context. Together with previous studies, our results suggest that across species, geographic song variation and the extent to which this variation functions in communication may be correlated with the accuracy with which song models are imitated during song development.

Habitat fragmentation effects and variations in repertoire size and degree of song sharing among close Dupont’s Lark Chersophilus duponti populations

We describe the song type repertoire variation and degree of song sharing in three isolated and declining Dupont’s Lark (Chersophilus duponti) populations located close to each other in eastern Spain, studied over two years. We found no differences between sites either in song rate or individual repertoire size. We detected great differences in song type diversity at the population level, ranging from five to 18 song types. We used, for the first time, the SIMPROF test, a method that objectively discriminates significant groups resulting from agglomerative clustering methods, to study geographic variation in bird song. We found four microdialects in the study area with a low degree of song sharing among populations, which may be related to the influence of habitat fragmentation and the song learning process and ecology of the species. We detected different patterns of song sharing among sites. All males of two populations shared about 80–100 % of their song types throughout the habitat patch. At the other site, we found two microdialects within the same habitat patch, where song types were only shared among neighbouring males. The high degree of song sharing found can be explained by the reduced dispersal movements of the species. We also detected a high consistency in the song types between years. The creation of corridors and habitat management in potential habitat patches surrounding Dupont’s Lark populations could act as stepping-stones, improving the connection between populations and thereby song transmission between patches.

Non-Breeding Song Rate Reflects Nutritional Condition Rather than Body Condition

Numerous studies have focused on song in songbirds as a signal involved in mate choice and intrasexual competition. It is expected that song traits such as song rate reflect individual quality by being dependent on energetic state or condition. While seasonal variation in bird song (i.e., breeding versus non-breeding song) and its neural substrate have received a fair amount of attention, the function and information content of song outside the breeding season is generally much less understood. Furthermore, typically only measures of condition involving body mass are examined with respect to song rate. Studies investigating a potential relationship between song rate and other indicators of condition, such as physiological measures of nutritional condition, are scant. In this study, we examined whether non-breeding song rate in male European starlings (Sturnus vulgaris) reflects plasma metabolite levels (high-density lipoproteins (HDL), albumin, triglycerides and cholesterol) and/or body mass. Song rate was significantly positively related to a principal component representing primarily HDL, albumin and cholesterol (and to a lesser degree plasma triglyceride levels). There was only a trend toward a significant positive correlation between song rate and body mass, and no significant correlation between body mass and the abovementioned principal component. Therefore, our results indicate that nutritional condition and body mass represent different aspects of condition, and that song rate reflects nutritional rather than body condition. Additionally, we also found that intra-individual song rate consistency (though not song rate itself) was significantly positively related to lutein levels, but not to body mass or nutritional condition. Together our results suggest that the relation between physiological measures of nutritional condition and song rate, as well as other signals, may present an interesting line of future research, both inside and outside the breeding season.

Macrogeographic variation in the song of the Mourning Warbler (Oporornis philadelphia)

Studies of macrogeographic variation in birdsong involve populations incapable of interbreeding because of physical barriers or separation by large distances. Different patterns have emerged from these studies such as (i) little or no variation exists among individuals or populations from the breeding range, (ii) individual variation is greater than among population variation resulting in no geographic structure, (iii) clinal variation, and (iv) macrogeographic variation where all individuals from several populations on the breeding range share a common song type forming a regional dialect or regiolect. I studied macrogeographic variation in song of the Mourning Warbler ( Oporornis philadelphia (A. Wilson, 1810)). The observed pattern was similar to the fourth category of geographic variation with regiolects. A Western regiolect extended from northern Alberta to western Ontario. An Eastern regiolect stretched eastward from western Ontario and Wisconsin to the Gaspé Peninsula and New England, then southward through the Appalachians to West Virginia. Nova Scotia and Newfoundland each had unique regiolects. Finally, I compared these results to other species with regiolects and assessed the ability of some deterministic hypotheses to explain song divergence (e.g., role of morphology, physical barriers, island isolation).

A Tradeoff Between Performance and Accuracy in Bird Song Learning

Some of nature’s most complex behaviors, such as human speech and oscine bird song, are acquired through imitative learning. Accurate imitative learning tends to preserve patterns of behavior across generations, thus limiting the scope of cultural evolution. Less well studied are the routes by which cultural novelties arise during development, beyond simple copy error. In this study we assess, in a species of songbird, the relationship in song learning between two potentially conflicting learning goals: accuracy in copying and maximization of vocal performance. In our study species, the swamp sparrow (Melospiza georgiana), vocal performance can be defined for a given song type and frequency range by the rate of note repetition (‘trill rate’), with faster trills being more difficult to sing. We trained young swamp sparrows with song models with experimentally modified trill rates and characterized both the accuracy and performance levels of copies. Our main finding is that birds elevated the trill rates of low-performance models, but at the expense of imitative accuracy. By contrast, birds reproduced normal and high-performance models with typically high accuracy in structure and timing. Developmental mechanisms that enable songbirds to balance imitative accuracy and vocal performance are likely favored by sexual selection and may help explain some current patterns of variation in birdsong. Such mechanisms may also explain how behaviors that are learned by imitation can nevertheless respond to selection for high-performance levels in their expression.

Male response to historical and geographical variation in bird song

In many species, individuals discriminate among sexual signals of conspecific populations in the contexts of mate choice and male-male competition. Differences in signals among populations (geographical variation) are in part the result of signal evolution within populations (temporal variation). Understanding the relative effect of temporal and geographical signal variation on signal salience may therefore provide insight into the evolution of behavioural discrimination. However, no study, to my knowledge, has compared behavioural response to historical signals with response to current signal variation among populations. Here, I measured the response of male white-crowned sparrows (Zonotrichia leucophrys) to historical songs compared with current songs from their local population, a nearby non-local population and a distant population. Males responded most strongly to current local songs, less, but equally, to historical local and current non-local songs, and least to songs of the distant population. Moreover, response to both temporal and geographical variation in song was proportional to how much songs differed acoustically from current local songs. Signal evolution on an ecological time scale appears to have an effect on signal salience comparable to differences found between current neighbouring populations, supporting the idea that behavioural discrimination among learned signals of conspecific populations can evolve relatively rapidly.

Central sources for acoustic variation in birdsong

Central sources for acoustic variation in birdsong

Central Contributions to Acoustic Variation in Birdsong

Birdsong is a learned behavior remarkable for its high degree of stereotypy. Nevertheless, adult birds display substantial rendition-by-rendition variation in the structure of individual song elements or "syllables." Previous work suggests that some of this variation is actively generated by the avian basal ganglia circuitry for purposes of motor exploration. However, it is unknown whether and how natural variations in premotor activity drive variations in syllable structure. Here, we recorded from the premotor nucleus robust nucleus of the arcopallium (RA) in Bengalese finches and measured whether neural activity covaried with syllable structure across multiple renditions of individual syllables. We found that variations in premotor activity were significantly correlated with variations in the acoustic features (pitch, amplitude, and spectral entropy) of syllables in approximately a quarter of all cases. In these cases, individual neural recordings predicted 8.5 +/- 0.3% (mean +/- SE) of the behavioral variation, and in some cases accounted for 25% or more of trial-by-trial variations in acoustic output. The prevalence and strength of neuron-behavior correlations indicate that each acoustic feature is controlled by a large ensemble of neurons that vary their activity in a coordinated manner. Additionally, we found that correlations with pitch (but not other features) were predominantly positive in sign, supporting a model of pitch production based on the anatomy and physiology of the vocal motor apparatus. Collectively, our results indicate that trial-by-trial variations in spectral structure are indeed under central neural control at the level of RA, consistent with the idea that such variation reflects motor exploration.

Local song elements indicate local genotypes and predict physiological condition in song sparrowsMelospiza melodia

Geographical variation in birdsong is taxonomically widespread and behaviourally salient, with females often preferring local over non-local song. However, the benefits associated with this preference remain poorly understood. One potential explanation is that song may reflect a male's place of origin and thus allow females to obtain genes well adapted to the local environment. We studied naturally occurring variation in the degree to which the elements of a male's song repertoire matched those of the local population ('syllable sharing') in migratory song sparrows (Melospiza melodia melodia). Syllable sharing was correlated with genetic similarity to the local population, suggesting that song reflects population of origin. Males sharing more syllables also had larger testosterone-dependent traits, fewer blood-borne parasites and reduced indicators of stress. Our findings are consistent with locally good genes models. Alternatively, immigrants' condition may suffer due to unfamiliarity with the breeding site or inability to match song elements during territorial interactions. Females preferring 'local-sounding' males may thus obtain genetic and/or direct benefits for their offspring.

Temporal variation in male chaffinch song depends on the singer and the song type

Studies of variation in bird song within a species have tended to concentrate on repertoire size and on song rate, while other aspects of song delivery have received little attention even though they are also likely to play an important part in the signalling process. We here examine the pattern of delivery of individual males' repertoires in the chaffinch (Fringilla coelebs) to identify variation in a range of temporal parameters of song delivery. Coefficients of variation differed between song units and across hierarchical levels. Basic units (syllables) were delivered with great temporal precision. The larger building blocks of a song (the different phrases and the flourish) showed the highest variability while variation for song duration itself was intermediate. Most variables showed consistent differences between males, but there were also consistent differences between song types within a male's repertoire, as well as between the same song types as sung by different males. This suggests an interaction between a male's phenotype and song production, but because of consistent differences between song types within repertoires, there is potential for selection to act on aspects of song delivery both of the individual and of the song type (i.e. the culturally transmitted unit).

GEOGRAPHIC SONG VARIATION AND ITS CONSEQUENCES IN THE GOLDEN BOWERBIRD

Abstract Geographic variation in birdsong is known from a variety of taxa, but is especially common and most frequently reported in passerines with resource-based territorial mating systems. To date, relatively little data have been presented on patterns of song variation in species with lek and leklike mating systems. In this paper, we describe geographic song variation in the Golden Bowerbird (Prionodura newtonia) a species with a leklike mating system. We compared recordings of the species advertisement song, collected from five isolated forest blocks from across the species range in northeastern Australia. Golden Bowerbird advertisement song shows marked geographic variation in form. All males within a population sing a song similar to each other, but distinct from that of males from other locations. The song traits important in discriminating between the songs of the different populations were bandwidth, number of peaks, dominant frequency, fundamental frequency, internote interval, and pureness. Dis...

MICROGEOGRAPHIC VARIATION IN CORN BUNTING (MILIARIA CALANDRA) SONG: QUANTITATIVE AND DISCRIMINATION ASPECTS

Abstract Geographic variation in bird song that is described as local song dialects refers to a mosaic pattern of distribution of songs in a population within the dispersal capacities of the species. Corn buntings (Miliaria calandra) in the region of Alentejo, Portugal, show such local dialects. However, an interesting aspect of this population is that song types are restricted to sub - groups of males within each dialect rather than all males singing all song types as in other populations. After describing the pattern of song type variation qualitatively (i.e. classifying spectrograms by eye), we used cross - correlation of spectrograms in quantitative comparisons. This confirmed the qualitative classification of songs into song type categories and showed a tendency for neighbouring males to have most similar songs. Males did not respond significantly more or less strongly to playback of different song types; however males clearly discriminated between different song types in a habituation paradigm.

Geographic Variation in Syllables of House Finch Songs

Bird songs often can be described as strings of individually distinct units called syllables. Toward furthering our understanding of the processes and consequences of vocal learning, geographic variation in vocalizations may be as important at the syllable level as it is at the song level. To examine geographic patterns of song variation at the syllable level in House Finches (Carpodacus mexicanus), we analyzed the syllable repertoires of 91 males at 21 sites in northern Colorado. Analyses were performed and comparisons were made among individual birds within and between sites. Using Jaccard's similarity coeffi- cient, we determined that syllable sharing among birds was significantly greater within sites and among sites less than 5 km apart than at greater distances. Within a site, any two birds usually did not share the majority of their syllable types, but discriminant function analysis showed that approximately 63% of the birds possessed syllable repertoires that matched most closely those of other birds at the same site. Less than 5% of the birds sang syllables that most closely matched those of birds at a site more than 20 km away. Our results suggest that House Finches in northern Colorado exhibit localized syllable sharing and that syllable sharing decreases exponentially with distance, but we found no evidence for discrete syllable dialects. Geographic variation in bird song typically has been evaluated using whole songs. Depending on how birds assess the singing behavior of other individuals and perceive dif- ferences in songs, it may be important to examine geographic variation and population dif- ferences at the syllable level as well. Received 8 January 1998, accepted 17 November 1998.

Song "Dialects" in Three Populations of White-Crowned Sparrows

The phenomenon of dialect variation in bird song, appearing as a consistent difference in the predominant song type between one population and another of the same species, has a special interest for biologists, serving as a focus for attention in discussion of such diverse topics as speciation (for example, Huxley, 1942; Mayr, 1942), learning (Thorpe, 1954, 1958) and the mechanisms of social communication (Marler, 1959). The White-crowned Sparrow (Zonotrichia leucophrys) affords one of the best known cases of such dialect variation among North American birds, and it has been commented upon by many who have observed this species (Blanchard, 1941; Peterson, 1941). Before the ontogenetic basis of such local song variation can be assessed and before its evolutionary significance can be satisfactorily determined, careful descriptions of the nature and extent of the variation are required. This paper seeks to provide some of this necessary information by describing song variation in the individual and in a population, both at one time and from year to year, and also by comparing songs in three populations, two adjacent and one distant.