Variability in blue whale acoustic behavior off southern California

To evaluate the acoustic behavior of blue whales (Balaenoptera musculus) located inshore and offshore of southern California, singular A and B calls, D calls, and AB phrases were analyzed from 12 mo of passive acoustic data collected at four locations within the Southern California Bight. The relative proportions of singular calls and phrases were used to evaluate spatial and temporal patterns in sound and song type usage, and singular call and phrase production rates were calculated to investigate spatial and temporal variability in call abundance. Blue whale sounds were recorded from spring through early winter, with the majority of all detections occurring between September and December. The proportions and production rates of singular calls and phrases varied between the inshore and offshore sites. In addition, the percentage of A units within repetitive song phrases was greater inshore than offshore, resulting from a higher proportion of AB song type inshore, in which A and B phrase units were alternating. The ABB song type, in which a single A unit was followed by multiple B units, was more common offshore. The observed differences in calling and singing behaviors may identify distinct and variable acoustic behavioral settings for blue whales off southern California.     

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.     

Experimental evidence that distinct song phrases in the Grey‐cheeked Fulvetta Alcippe morrisonia permit species and local dialect recognition

Birds with small song repertoires have a limited number of song types which may serve multiple functions. The Grey‐cheeked Fulvetta Alcippe morrisonia is a non‐migratory species of lowland forests in Taiwan. Its song consists of two distinct phrases: a whistled phrase and a harmonic one. Each individual usually sings only one type of whistled phrase, and the geographical patterns of songs can be distinguished by the motif of this phrase. We proposed a dual adaptation hypothesis for the functions of these two phrases. Playback experiments including six sound stimuli (familiar whistled phrases, familiar harmonic phrases familiar complete songs, foreign whistled phrases, foreign harmonic phrases and foreign complete songs) were conducted at 12 sites in the Shoushan Nature Park of Kaohsiung, Taiwan. Grey‐cheeked Fulvettas came closer to the playback speaker and increased counter‐singing more in response to the familiar whistled phrase (local dialect) than to a foreign whistled phrase (distant dialect). However, birds responded equally to the playback of harmonic stimuli from familiar and foreign sources. We suggest that in this species, whistled phrases are used for local recognition and harmonic phrases are used for species recognition in short‐range communication.     

Preferences and predispositions of female canaries (Serinus canaria) for loud intensity of male sexy phrases

In the present study, we tested the effect of song amplitude on intersexual relationships. To evaluate preferences and predispositions of female canaries for amplitude levels of male song, we conducted two experiments using both females raised in acoustic isolation and females raised in an aviary under 'normal' acoustic conditions. The songs used in both experiments followed the same pattern: one reactive phrase surrounded by two nonreactive phrases. The first experiment consisted of testing female preferences for weak, normal, or loud amplitudes of the reactive phrase (i.e. these reactive phrases provoke sexual stimulation in females). In a second experiment, we tested female preferences for weak, normal, or loud amplitudes of the nonreactive phrases. These two experiments allowed us to evaluate female preferences for intensity levels of reactive and nonreactive phrases. In the first experiment, all females significantly prefered loud and normal reactive phrases, whereas the second experiment showed that loud nonreactive phrases do not necessarily provoke more responses than other nonreactive phrases. Female canaries were, thus, more stimulated by the intensity level of a particular part of the song. Both females raised in acoustic isolation and in normal acoustic conditions responded in the same way. We can therefore suppose that learning, through acoustic experience, has little influence on preference development for amplitude levels.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 808–814.     

Unusual song of an individual Cyprus Scops Owl Otus cyprius (Aves: Strigidae)

Cyprus Scops Owl, Otus cyprius, has recently been split from Eurasian Scops Owl, Otus scops, partly because of song differences. Spectrographic analysis of a more recent O. cyprius song recording shows that it differs from that of O. scops in phrase length and frequency more than previously analysed recordings. The recorded song is also most unusual in possessing two phrases each containing 11 consecutive quiet notes; these two phrases are also remarkably similar in pattern, timing and amplitude. Previously only three consecutive quiet notes were known from O. cyprius though so far its multiple quiet note phrases have been little studied.     

Female recognition of trills in the male calling song of the field cricket,<Emphasis Type="Italic"> Teleogryllus taiwanemma</Emphasis>

The calling song of the field cricket, Teleogryllus taiwanemma, is usually considered to consist of sequences of separate chirps. However, sometimes it comprises a phrase of several chirps in a row, with one long chirp (chirp) and a few short chirps (trills). In this study, I compared the phrase containing only chirps with that containing both chirps and trills by analyzing male songs and conducting playback experiments of male songs to females. The song analyses showed significant differences between chirps and trills for all song parameters except bandwidth. To test whether female preference differed with respect to the two phrases, I performed two-speaker playback experiments. When the same numbers of phrases were presented per unit time, females preferred the song with trills to that without trills. This result may reflect female preference for songs with greater sound density. In subsequent playback experiments, I equalized the total sound duration per unit time (duty cycle) in songs with and without trills. The numbers of females that preferred songs with and without trills did not differ significantly. This suggests that trills can attract females like chirps do, even though the two sounds have different components.     

Song structure variability in passerine birds: Random variation or direct informative changes

The variability of the fine song structure was studied in the wood warbler (Phylloscopus sibilatrix), willow warbler (Ph. trochilus), greenish warbler (Ph. throchiloides viridanus), chaffinch (Fringilla coelebs), and gray shrike thrush (Colluricincla harmonica). The increase in the number of similar elements per phrase is shown to be related to the conspecific and heterospecific male-male song interactions in these birds. The responses of wood warbler males to playback conspecific songs with standard and prolonged (in the number of similar elements) second phrases differ significantly. The initial phrases of willow warbler songs become significantly longer in the populations with a high density as compared to those in populations of low density. The increase in the variability of both phrase combinations and song duration is shown to be related also to the song interaction with conspecific males for the willow warbler, greenish warbler, chaffinch, and gray shrike thrush. The within-song type variations turned out to play an important role during male-male interactions of different species. The results obtained suggest that similar ways of song responses may be quite widespread among passerine birds and reflect the general principles of changes in the song structure during acoustic interactions.     

Versatility and Stereotypy of Free-Tailed Bat Songs

In mammals, complex songs are uncommon and few studies have examined song composition or the order of elements in songs, particularly with respect to regional and individual variation. In this study we examine how syllables and phrases are ordered and combined, ie “syntax”, of the song of Tadarida brasiliensis, the Brazilian free-tailed bat. Specifically, we test whether phrase and song composition differ among individuals and between two regions, we determine variability across renditions within individuals, and test whether phrases are randomly ordered and combined. We report three major findings. First, song phrases were highly stereotyped across two regions, so much so that some songs from the two colonies were almost indistinguishable. All males produced songs with the same four types of syllables and the same three types of phrases. Second, we found that although song construction was similar across regions, the number of syllables within phrases, and the number and order of phrases in songs varied greatly within and among individuals. Last, we determined that phrase order, although diverse, deviated from random models. We found broad scale phrase-order rules and certain higher order combinations that were highly preferred. We conclude that free-tailed bat songs are composed of highly stereotyped phrases hierarchically organized by a common set of syntactical rules. However, within global species-specific patterns, songs male free-tailed bats dynamically vary syllable number, phrase order, and phrase repetitions across song renditions.     

Singing through winter nights: Seasonal and diel occurrence of humpback whale (Megaptera novaeangliae) calls in and around the Gully MPA,offshore eastern Canada

Humpback whale use of areas off eastern Canada is poorly understood, a knowledge gap that could impact future conservation efforts. We describe the acoustic occurrence of humpback whales in and around the Gully Marine Protected Area (MPA), an eastern Scotian Shelf submarine canyon. Near‐continuous acoustic recordings sampling at 16 kHz were collected from the MPA and nearby slope areas from October 2012 to September 2014 using near‐bottom recorders. In an offshore region where humpbacks were thought to be rare, we observed calls from October to June with a peak in song and nonsong calls in December and January. This suggests that some individuals occur in Canadian waters in winter and the Gully region may be a North Atlantic humpback whale migratory corridor. Calls were predominantly songs indicating potential mating activities. Song and nonsong calls occurred more at sunset and during hours of darkness than during daylight. This study improves our understanding of the seasonal occurrence of humpback whales on the Scotian Slope and, more specifically, their use of an offshore protected area.     

Lesions targeted to the anterior forebrain disrupt vocal variability associated with testosterone‐induced sensorimotor song development in adult female canaries,Serinus canaria

Learned communication was a trait observed in a limited number of vertebrates such as humans but also songbirds (i.e., species in the suborder passeri sometimes called oscines). Robust male‐biased sex‐differences in song development and production have been observed in several songbird species. However, in some of these species treating adult females with testosterone (T) induced neuro‐behavioral changes such that females become more male‐like in brain and behavior. T‐treatment in these adult females seemed to stimulate sensorimotor song development to facilitate song masculinization. In male songbirds it was known that the lateral magnocellular nucleus of the anterior nidopallium (LMAN) played a modulatory role during song development. LMAN was androgen sensitive and may be a key target of a T‐induced recapitulation of a developmental process in adult females. This hypothesis was tested. Adult female canaries were given either a chemical lesion of LMAN or a control sham‐surgery. Prior to surgery birds were individually housed for 2‐weeks in sound‐attenuated chambers to record baseline vocal behavior. Post‐surgery birds were given 1‐week to recover before subcutaneous implantation with silastic capsules filled with crystalline‐T. Birds remained on treatment for 3‐weeks (behavioral recordings continued throughout). Birds with a lesion to LMAN had less variability in their song compared with controls. The diversity of syllable and phrase type(s) was greater in sham controls as compared with birds with LMAN lesions. Birds did not differ in song rate. These data suggested that the sustention and conclusion of T‐induced sensorimotor song development in adult female canaries required an intact LMAN. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 3–18, 2016     

Structure,syntax and “small-world” organization in the complex songs of California Thrashers (Toxostoma redivivum)

We describe songs of the California Thrasher (Toxostoma redivivum), a territorial, monogamous species whose complex songs are composed of extended sequences of phonetically diverse phrases. We take a network approach, so that network nodes represent specific phrases, and links or transitions between nodes describe a subgroup structure that reveals the syntax of phrases within the songs. We found that individual birds have large and largely distinct repertoires, with limited phrase sharing between neighbours and repertoire similarity decaying between individuals with distance apart, decaying also over time within individuals. During song sequences, only a limited number of phrases (ca. 15–20) were found to be actually “in play” at any given time; these phrases can be grouped into themes within which transitions are much more common than among them, a feature contributing to a small-world structure. It appears that such “small-world themes” arise abruptly, while old themes are abandoned more gradually during extended song sequences; most individual thrashers switch among 3–4 themes over the course of several successive songs, and some small-world themes appear to have specific roles in starting or ending thrasher songs.     

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.     

Sensitivity of California Thrashers (Toxostoma redivivum) to song syntax

Many birds have songs with variable structure and sequences. In earlier studies, we characterized some features from the song structures of California Thrashers (Toxostoma redivivum). In the Thrashers, there were a large number of phrase types, dozens to hundreds and the songs that were sequences of these many phrases were not random, but show some structure referred to as syntax. For example, a syntactic rule might be that phrase type A can be followed by phrase type B, but not type C. We, along with others, have assumed that syntax is an important feature of songs. This paper describes an experimental attempt to determine that syntax is important to California Thrashers by recording the reaction of territorial thrashers to playbacks of other thrasher songs, some of which obeyed the syntax rules we had discovered while others violated those rules. We also obtained video recordings of their behaviour near the playback speakers. We observed differences in the reactions to the birds that heard these two types of playbacks. Resident males reacted to either playback type, but more strongly when the original order was preserved. We observed difference in their behavioural response to correct or altered syntax. This indicates that the syntax of their songs is perceived in territorial defence by the birds.     

Mechanisms of song differentiation in introduced populations of Chaffinches Fringilla coelebs in New Zealand

Chaffinches Fringilla coelebs were introduced to New Zealand from Great Britain over 100 years ago, and since then their songs have diverged from British ones in both syllable structure and basic organization of syllable sequences. The New Zealand populations seem to be unique in that their songs have undergone differentiation of trill segments by progressive elaboration of syllable morphology and hp ascending and descending changes of pitch. Published sonagrams of British song types have significantly more trill phrases and significantly fewer syllables in the end phrase than do Yew Zealand ones. Many New Zealand song types have much elaborated end phrases and concomitantly simpler trill segments, with songs quite commonly having only one trill phrase. This reversal of complexity between the trill and end phrase in New Zealand seems to have been derived by progressive reduction of the ultimate trill phrase to one syllable, and by recombination of end phrase syllables from different song types into one compound end phrase. The significance of the increased complexity in the end phrases of many song types may relate to the sound transmission properties of dense pine forests in New Zealand, in which Chaffinches are ubiquitous. Elaborate end phrases degrade much less from reverberation in pine forests because individual syllables have more dispersed temporal patterning.
Recombination of syllables to form new song types is a major mechanism of song differentiation in New Zealand. Although whole song copying is the predominant mode of replication, very few song types in a locality sample are composed of a unique set of syllables. Rather, song types in an area are interconnected by different combinations of shared syllables, suggesting that the incorporation of some local syllables in a bird's repertoire is sufficient to signal its status as a member of a neighbourhood and also allows the evolution of broadcast complexity.     

Conveying information with one song type: changes in dawn song performance correspond to different female breeding stages

Many bird species participate in dawn singing, a behaviour categorized by intensive singing at dawn; however, many of these species deliver only one song type at dawn. While there are many proximate and ultimate hypotheses for why birds sing at dawn, little is known about whether males are able to vary one simple song to convey different information. We used autonomous acoustic recorders to record dawn songs of field sparrows and quantified three parameters of singing performance: 1) bout length, 2) song rate, and 3) song complexity. We found that males sang the longest dawn bouts during their mate's fertile period, the highest song rates during the post-fertile period, and the most complex songs during the pre-fertile period. The change in dawn singing behaviour with their mate's breeding stage suggest the purpose of dawn song may be context dependent. Our results demonstrate that male field sparrows, while only having a single song type sung at dawn, may convey information for both intra- and intersexual purposes. While it is generally assumed that dawn song has a specific function, the variability in the duration, rate, and complexity of dawn song in field sparrows suggests that they are conveying different information and that dawn song likely has multiple functions.     

Plain wrens Cantorchilus modestus zeledoni adjust their singing tempo based on self and partner's cues to perform precisely coordinated duets

Precise coordination appears to be an important signal in several duetting species. However, little attention has been directed to the proximate mechanisms that might drive this behavior. To perform highly coordinated duets, individuals can either have an intrinsic fixed singing tempo or modify their singing tempo based on cues in their own and their partner's songs. In this study I determined whether autogenous and/or heterogenous factors are associated with duet coordination in plain wrens Cantorchilus modestus zeledoni by analyzing recorded duets from 8 territorial pairs in the field. Previous research has determined that plain wrens perform highly coordinated antiphonal duets with almost no overlap. I found that to achieve such precise coordination individuals perform phrase‐by‐phrase modifications to the duration between two consecutive phrases (inter‐phrase interval) based on a) whether their song is answered, b) the phrase type used in the duet and c) the position of the inter‐phrase interval within the duet. Moreover, there are several sex differences in how individuals use these cues to modify their inter‐phrase intervals. Females produce longer inter‐phrase intervals when their mates do not answer a phrase, whereas males produce shorter inter‐phrase intervals when their mates do not answer. Females modify their inter‐phrase intervals based only on the phrase type their mates sing, whereas males modify their inter‐phrase intervals based on both the phrase that they sing and the phrase the females use to answer. Both males and females produce longer inter‐phrase intervals for longer phrase types sung by their partners, but males do so with more precision than do females. Finally both sexes increase their inter‐phrase intervals as the duet progresses. That precise coordination is achieved by a complex and dynamic process supports the idea that this behavior could signal pair bond strength.     

NORTH PACIFIC HUMPBACK WHALE SONGS: A COMPARISON OF SOUTHEAST ALASKAN FEEDING GROUND SONGS WITH HAWAIIAN WINTERING GROUND SONGS

Humpback whales sing long, complex songs on their wintering grounds. On 25 August 1979 and 3 September 1981, we made recordings of humpback whale songs in southeastern Alaska, showing that humpback whales also sing on the summer feeding grounds. Both these Alaskan samples are songs in that they are repeating cyclical sound patterns and follow the known structure for humpback whale song. The Alaskan songs contain all the same material sung in the same order as that heard off Mexico and Hawaii in the surrounding wintering seasons. However, song, theme and some phrase durations are abbreviated in the Alaskan songs. The recording of these two songs represents the full sample of song recorded from 155 days over five years of attempting to record humpback whale song in Alaskan waters.