Minimal similarity in songs suggests limited exchange between humpback whales (Megaptera novaeangliae) in the southern Indian Ocean

Comparing humpback whale song from different breeding assemblages can reveal similarities in song due to acoustically interacting males, and therefore indirectly test whether males from different breeding sites are mixing. Northern Hemisphere song comparisons illustrated that whales within ocean basins share similar songs and are subpopulations within a larger population, whereas whales in different ocean basins are isolated populations and therefore do not share songs. During the 2006 breeding season, recordings were collected in Madagascar and Western Australia, and were compared visually plus aurally. Both regions shared one theme, whereas each region had four and six private themes, respectively. This study had a substantially low number of shared themes. The co‐occurrence of one theme was interpreted as an indication of limited exchange between these breeding assemblages, and we speculate that limited song similarity is due to inter‐oceanic interactions. Male(s) from an Indian Ocean breeding group could be exposed to novel song when they geographically overlap, and acoustically interact, with males from a different ocean basin. Novel song could induce rapid temporal changes as new song content is incorporated, thereby minimizing song similarities between that breeding group and other Indian Ocean breeding groups that were not exposed to the novel song.     

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.     

Song‐type sharing in a population of Song Sparrows in the eastern United States

Male Song Sparrows (Melospiza melodia) sometimes interact with neighboring territory owners by song‐type matching or repertoire matching. In some Song Sparrow populations, levels of song sharing are high and most neighbors can interact by matching, but levels of song sharing are much lower in other populations, limiting the degree to which males can match their neighbors. One explanation for variation in sharing levels is that the importance of song‐type and repertoire matching, and therefore the extent of song sharing, varies geographically in North America, being greater in western populations than eastern populations. However, to date, two studies of eastern populations have provided conflicting evidence concerning levels of song sharing by Song Sparrows. Thus, we measured sharing of whole songs and introductory phrases of songs between males with adjacent territories in another population of Song Sparrows in the eastern United States (North Carolina), near the eastern and southern limits of the species’ breeding range. Males (N = 17) in our study shared an average of only 8.7% of their song types with neighbors, and more than half of neighbor pairs shared no whole songs. Sharing of introductory phrases was more common (mean = 22.8%). The level of whole song sharing in our study is the second lowest yet reported for any Song Sparrow population, supporting the hypothesis that sharing is generally lower in eastern than in western populations.     

Ecological and Phylogenetic Effects on Song Sharing in Songbirds

As a consequence of vocal learning, the songs of male songbirds often vary geographically. We examined three proximate hypotheses that predict variation in the incidence of local song sharing among species: the annual cycle, breeding season duration, and epiphenomenon hypotheses. To test these hypotheses, we compiled data from the literature on local song sharing, annual cycle, breeding location isophane (an index of breeding season duration), repertoire size, and phylogenetic relationships of 65 populations in the family Fringillidae. Mapping characters on the phylogenetic tree revealed that local song sharing, migratory status, and breeding location isophane were randomly distributed on the phylogeny. Breeding isophane and migratory status were themselves correlated and had significant effects on the probability of sharing local songs. As predicted by the annual cycle and breeding season duration hypotheses, males in sedentary populations and populations breeding at low isophanes were more likely to share local songs. In subsets of the data, the annual cycle hypothesis received more support than did the breeding season duration hypothesis. Neither hypothesis explained more than 17% of the variation in the incidence of song sharing, and we suggest that detailed information on song function, male dispersal, and constraints on the timing of song learning will be needed to better predict the occurrence of local song sharing.     

Differences in Frequency of Shared Song Types Enables Neighbour‐Stranger Discrimination in a Songbird Species with Small Song Repertoire

Acoustic Neighbour‐Stranger (N‐S) discrimination is widespread in birds and has evolved to settle territorial disputes with low costs. N‐S discrimination was found both in song‐learning oscines and non‐song‐learning bird taxa, irrespective of the repertoire sizes they have. Therefore, it seems that more than just a single mechanism enable N‐S discrimination. Species with larger repertoires, where males have unique phrases or syllables may rely on such interindividual differences. The majority of birds have rather small repertoires, which often are shared among neighbours. In this case, males are facing the problem of individual recognition when rivals produce songs, at least superficially, identical. To better understand the acoustic basis of N‐S discrimination in species with small and shared repertoires, I studied the ortolan bunting (Emberiza hortulana). Males of this small oscine species are able to N‐S discrimination based on a single song rendition when presented in a playback experiment, regardless of song‐type diversity and song‐sharing level within a particular population. It was also found that songs of the same type sung by different males differ in the frequency of the initial song phrases and these differences persist over years. Here, I tested whether males are able to discriminate among the natural songs and the artificially modified songs of their neighbours in which the frequency was experimentally changed by relatively small value in comparison with the variation range found in this population. Subjects responded significantly more aggressively to the songs with an artificially modified frequency, suggesting that males treat such songs as having come from the repertoire of a non‐neighbour. These results confirm an earlier prediction that differences in the frequency of shared song types enable N‐S discrimination. The study presents one of the possible mechanisms enabling N‐S discrimination in songbirds with small repertoires and stress the role of within‐song‐type variation, which is still understudied song characteristic.     

Responses of a sub-oscine bird during playback: effects of different song variants and breeding period

Vermilion flycatchers (Pyrocephalus rubinus) vary their song rate and song length across the breeding season. Males sing more and longer songs after nest construction than before. Here we explored the possibility that this variation is meaningful to territorial males. Using a playback approach, we tested several males with different variations in song output (i.e. variations in song length and song rate) in different periods of the breeding season (i.e. before and after the onset of nest construction). We found that males call more in response to playbacks of long and short songs before the onset of nest construction. However, after nest construction began they responded flying more when exposed to long songs than to short songs. These results show that vermilion flycatcher discriminates between different variants of song length, and suggest that males react to long songs as if they were more threatening signals than short songs, especially after the onset of nest construction. We did not find evidence of males discriminating between a high and a low song rate. We discuss some possible implications for song function in this sub-oscine species, and compare these findings with other results in oscine species.     

Whip it good! Geographic consistency in male songs and variability in female songs of the duetting eastern whipbird Psophodes olivaceus

Geographic variation in male bird songs has been studied extensively, but there have been few investigations of geographic variation in female songs or sex differences in patterns of geographic variation. We compared patterns of variation in male and female songs of eastern whipbirds Psophodes olivaceus by analyzing recordings from 16 populations across the species’ geographic range in eastern Australia. We found remarkably different patterns of geographic variation between the sexes. Female eastern whipbird songs are easily categorized into discrete song types. Song types are shared between nearby females, but female songs show pronounced differences at a continental scale. In contrast, male eastern whipbird songs show high consistency throughout the species’ geographic range. All recorded males share the ability to transpose the frequency of the introductory whistle and most recorded males share the ability to vary the direction of the slope of the terminal whip crack. For eight of nine measured variables, female songs show significantly higher levels of variation than male songs. We discuss whether sex differences in dispersal, song learning strategies, and song function may explain these sex differences in patterns of song variation. We suggest that eastern whipbirds have experienced a decoupling of male and female song learning strategies and that the songs of each sex have responded to different selective pressures in the context of countersinging interactions. We speculate that consistency in male songs throughout the geographic range of eastern whipbirds may arise through female preference for males that perform large bandwidth whip cracks.     

Whip it good! Geographic consistency in male songs and variability in female songs of the duetting eastern whipbird Psophodes olivaceus

Geographic variation in male bird songs has been studied extensively, but there have been few investigations of geographic variation in female songs or sex differences in patterns of geographic variation. We compared patterns of variation in male and female songs of eastern whipbirds Psophodes olivaceus by analyzing recordings from 16 populations across the species' geographic range in eastern Australia. We found remarkably different patterns of geographic variation between the sexes. Female eastern whipbird songs are easily categorized into discrete song types. Song types are shared between nearby females, but female songs show pronounced differences at a continental scale. In contrast, male eastern whipbird songs show high consistency throughout the species' geographic range. All recorded males share the ability to transpose the frequency of the introductory whistle and most recorded males share the ability to vary the direction of the slope of the terminal whip crack. For eight of nine measured variables, female songs show significantly higher levels of variation than male songs. We discuss whether sex differences in dispersal, song learning strategies, and song function may explain these sex differences in patterns of song variation. We suggest that eastern whipbirds have experienced a decoupling of male and female song learning strategies and that the songs of each sex have responded to different selective pressures in the context of countersinging interactions. We speculate that consistency in male songs throughout the geographic range of eastern whipbirds may arise through female preference for males that perform large bandwidth whip cracks.     

Territory establishment,song learning strategies and survival in song sparrows

In most songbirds, the processes of song learning and territory establishment overlap in the early life and a young bird usually winds up with songs matching those of his territorial neighbors in his first breeding season. In the present study, we examined the relationships among the timing of territory establishment, the pattern of song learning and territorial success in a sedentary population of song sparrows (Melospiza melodia). Males in this population tend to learn their songs from their neighbors and consequently they show high song sharing with neighbors and use these shared songs preferentially in interactions with them. Males also show significant variation in the timing of territory establishment, ranging from their natal summer to the next spring. Using a three-year dataset, we found that the timing of territory establishment did not systematically affect the composition of the song repertoire of the tutee: early establishers and late establishers learned equally as much from their primary tutors and had a similar number of tutors and similar repertoire sizes, nor did timing of territory establishment affect subsequent survival on territory. Therefore, the song-learning program of song sparrows seems versatile enough to lead to high song sharing even for birds that establish territories relatively late.     

Song characterization in the spectacled warbler (Sylvia conspicillata): a circum-Mediterranean species with a complex song structure

The spectacled warbler (Sylvia conspicillata) is a small passerine with a patchy distribution throughout the circum-Mediterranean region, including the North Atlantic archipelagos of Madeira, Canary Islands and Cape Verde. Here we characterize the species song structure on the island of Fuerteventura, quantifying repertoire size, inter- and intra-individual spectrographic variation, to determine whether acoustic variation occurred within an island population. Male song display was organized in song bouts of a variable number of song phrases, which in turn were made up of 4–69 syllables. We classified syllable types to derive a measure of repertoire size (number of different syllables) per song bout, and then used rarefaction methods to calculate the estimated repertoire size for our population of males. Three categories of song bout length were considered in analyses: short song bouts of 10 phrases, average bouts of 19 phrases and long bouts of ≥ 29 phrases. The observed and estimated repertoire size per male (between 43 and 126 syllables per male) increased with song bout duration, although the relationship was not significant for the estimated values. To test whether songs could be individually specific, we measured 11 spectrotemporal parameters of the song. A discriminant analysis using these variables performed poorly in classifying songs to the individuals that uttered them, but we found less variation in the individual than in the population for three out of the 11 variables. These individually specific variables, involving the first or the most common syllable of the song, the trill, were the duration of the first syllable of the phrase, the duration and the dominant frequency of the trill syllable. Our study emphasizes the complexity of spectacled warbler songs, in which males continuously add novel syllables over the entire song bout. This complexity appears to be determined by individual innovation capabilities rather than by the behaviour of copying neighbour repertoires, since songs of close birds were not more similar than songs from far-away territories.     

Ecological effects on song learning: delayed development is widespread in wild populations of brown-headed cowbirds

The timing and extent of early exposure to conspecific song can have critical influence on subsequent male vocal development in songbirds. Opportunities to memorize local song models may vary among populations depending on local ecological conditions that determine the length of the breeding season. In populations with comparatively short breeding seasons, such as northern or high-elevation populations, restricted access to local songs may delay development in a large proportion of juveniles. Previous studies have described extreme examples of delayed development in high-elevation populations of brown-headed cowbirds, Molothrus ater, in the Sierra Nevada of California, U.S.A. In the current study, we determined that delayed development also occurs in a low-elevation population located at a more northerly latitude than those in the Sierra. We recorded two kinds of songs from yearling and adult males who had been given testosterone (testosterone increased song output but did not change the nature of songs in males' repertoires) soon after being trapped at two adjacent sites in New York state, U.S.A. The average size of ‘perched’ song repertoires of 17 yearlings was significantly smaller than that of 20 local adults (2.8 versus 4.6 types, respectively) and yearlings generally lacked the shared songs typically found in adult repertoires. Only 40% of yearlings trapped at one site produced the correct local dialect ‘flight whistle’ compared with 91.7% of adults. These results strongly suggest that juvenile access to local songs is also restricted in this population and that delayed vocal development is widespread in cowbirds. In addition, these findings indicate that reliance on field recordings may underestimate adult-yearling differences in vocal competency in cowbirds because yearlings that sing readily in nature may not be representative of yearlings in general, a result that may also apply to other songbird species.     

Changes in Performance of Shared and Unshared Songs Within and Between Years in the White‐crowned Sparrow

Song of passerine birds is one of the few animal signals that is learned and that improves with practice. Vocal practice is crucial early in life to perfect a song imitation, but it also occurs throughout life and may continue to improve aspects of song performance. Differences in song performance among males that share song types, that is sing structurally similar songs may be particularly salient to receivers. We here test the hypothesis that aspects of song performance improve in a songbird species that deletes song types from its repertoire early in the first breeding season to share their final single song type with territorial neighbours. Over 3 yrs, we recorded songs in a population of Puget Sound white‐crowned sparrows Zonotrichia leucophrys pugetensis and measured percentage peak performance and consistency thereof in all of the song types in each male's repertoire. We found that within the first year on territory, percentage peak performance was higher in shared than unshared songs but did not change from first to second recording. Contrary to the hypothesis that song performance improves with age, song performance declined from the first to the second year. Our results support the hypothesis that high‐performance singers share songs. We did not find support for song performance improving within or between years, like it does in some other songbird species.     

Male song diversity and its relation to breeding success in southern house wrens Troglodytes aedon chilensis

Theory proposes an adaptive relationship between male song complexity, including large song repertoires, and improved breeding success. Evidence supporting these relationships exists but is sometimes mixed or weak. Here we provide a first comprehensive study of the relationship between male song diversity and breeding success in a non‐migratory, austral population of house wrens Troglodytes aedon chilensis breeding in Mendoza, Argentina. During a two‐year field study, we measured breeding success for a population of 62 males and recorded more than 34 000 songs from a subsample of 26 males. For the latter subsample, we tested for correlations between six measures of song diversity and four canonical measures of annual breeding success. Males that sang with greater overall syllable type diversity and that had larger song repertories paired with females that bred earlier and laid more eggs over the course of the breeding season. However, these males also showed lower levels of immediate song type diversity, as measured by the Levenshtein distance between successive songs. We discuss implications for the evolution of song complexity in this exceptionally widespread species and the selective mechanisms that might influence song complexity in resident populations in the Neotropics compared to migratory populations in the northern hemisphere.     

Identification of different song types in the European Nightjar Caprimulgus europaeus

ABSTRACT

Capsule: Two distinct song types were identified for male European Nightjars Caprimulgus europaeus with their relative frequency of use changing through the breeding season, indicating a possible link to paired status.

Aims: To test whether two song types could be defined in audio recordings and whether use differed in relation to the paired status of males.

Methods: Unattended acoustic recording devices were placed at a Nightjar study site in Nottinghamshire, United Kingdom, and recordings of churring vocalizations were made during two periods of the breeding season. These recordings were then analyzed to identify the presence/absence of the song terminal phrase and associated audible features.

Results: Two distinct song types were identified in the recorded audio data that differed in their terminal phrasing and overall song duration. The number of Nightjar songs with a terminal phrase increased significantly between the two sampling periods, from lower levels during the site arrival period, to higher levels during the first clutch initiation period.

Conclusion: This study showed that the use of Nightjar song types appears to vary through the breeding season, with males being more likely to produce song with a terminal phrase during the first clutch initiation period, when they are more likely to be paired or in the presence of a female. The unattended acoustic recording method may provide a minimally intrusive means of assessing the number of Nightjar breeding pairs and not just singing males.     

Sexually dimorphic phrase organization in the song of the indris (Indri indri)

Animal acoustic communication often takes the form of complex sequences, composed of multiple distinct acoustic units, which can vary in their degree of stereotypy. Studies of sequence variation may contribute to our understanding of the structural flexibility of primates' songs, which can provide essential ecological and behavioral information about variability at the individual, population, and specific level and provide insights into the mechanisms and drivers responsible for the evolutionary change of communicative traits. Several methods have been used for investigating different levels of structural information and sequence similarity in acoustic displays. We studied intra and interindividual variation in the song structuring of a singing primate, the indri (Indri indri), which inhabits the montane rain forests of Madagascar. Indri groups emit duets and choruses in which they combine long notes, short single units, and phrases consisting of a variable number of units (from two to six) with slightly descending frequency. Males' and females' contributions to the song differ in the temporal and frequency structure of song units and repertoire size. We calculated the similarity of phrase organization across different individual contributions using the Levenshtein distance, a logic distance that expressed the minimum cost to convert a sequence into another and can measure differences between two sequences of data. We then analyzed the degree of similarity within and between individuals and found that: (a) the phrase structure of songs varied between reproductive males and females: female structuring of the song showed a higher number of phrases if compared to males; (b) male contributions to the song were overall more similar to those of other males than were female contributions to the song of other females; (c) male contributions were more stereotyped than female contributions, which showed greater individual flexibility. The picture emerging from phrase combinatorics in the indris is in agreement with previous findings of rhythmic features and song repertoire size of the indris, which also suggested that female songs are potentially less stereotyped than those of males.     

珠颈斑鸠繁殖期占据领域鸣声特征及行为

2003年4～6月,在四川省南充市通过野外观察、录音、室内计算机处理及声谱分析对珠颈斑鸠繁殖期占据领域鸣声特征及行为做了研究。结果表明：珠颈斑鸠有一般占据和召唤配偶共同占据两类鸣声,两类鸣声雌雄不同,但均由3音节组成;其鸣唱具有应答性,且每次在各栖位点的鸣唱顺序大致相同;日鸣唱频次变化大,具3个高峰期;繁殖各时期鸣唱频次变化亦大。     

The typological organization and microgeographical variation of chaffinch (<Emphasis Type="Italic">Fringilla coelebs</Emphasis> L.) songs in the population of the Curonian Spit

The song repertoire of many sparrow species (Passeriformes) has not one but several song types. In the investigated chaffinch population (Fringilla coelebs L.), we revealed 22 types of songs, of which four turned out to be rare (they were found in 1—2 points), and five song types were combined (they consisted of phrases of different song types). The average size of the chaffinch repertoire in the Curonian Spit was represented by 2—3 song types (max of 6 song types and min of 1 song type). The variation in song types considered by us can speak for genetic heterogeneity.     

Age-related changes in song repertoire size and song type sharing in the Whinchat Saxicola rubetra

In many oscine passerines males’ songs, the repertoire size increases with age. At the same time it often remains unknown when and where males learn new songs. To infer the Whinchat Saxicola rubetra song learning strategy, we described and catalogued song-type repertoire, revealed age differences and examined song sharing strategies among neighbouring and distant males. We recorded song vocalizations of 40 males in a limited (104 ha) study plot during four years. Whinchats produce short and discrete songs with clear intersong pauses. In total 45 song types were allocated, the individual repertoire size averaged 23.5 ± 7.6 song types (range 9–34 song types). The males’ age significantly influenced the song-type repertoire size. The second calendar year (first breeding) males had a lower repertoire size than the older males. The majority of song types were shared by less than half of males in our sample. The Jaccard similarity indexes varied from 0.5 to 0.7. We could not find a relationship between males’ song sharing and geographic distances between their nests. We assume that Whinchat males learned new songs in the local population before territory establishment.     

白头鹎繁殖期鸣声行为的研究

利用计算机鸣声分析技术对白头鹎繁殖期的求偶炫耀鸣唱、晨鸣、遇险告警惊叫等鸣声的特征进行分析，以探讨鸣声特征与行为的关系。白头鹎繁殖前期待有的求偶炫耀鸣唱婉转多变，频率一般变化在１．９－３．５ｋＨｚ之间，另一类出现在繁殖前、中期的炫耀鸣唱急促而响亮，音节变化快且频率高（变化范围约３．４－４．４ｋＨｚ）；最鸣和繁殖期特有的其它鸣声，音节清晰，响度较大，能量主要集中在２－３ｋＨｚ之间，可能具有宣告领域的