Longer Syllables Research Articles

Tonal context influences tone-duration interaction: Evidence from Cantonese.

Phonetic typological studies suggest that syllable duration is inversely correlated with the accompanying tone's approximate average f0, and tones with dynamic f0 movement tend to be in longer syllables rather than shorter ones. Systematic instrumental investigations on tone-duration interaction remain scant, however; existing studies might be confounded as tonal context may impact duration realization due to phonetic constraints on tonal movement. This study investigates the effect of tonal environment on the durational realization of tones in Cantonese, showing that tone-dependent duration variation is governed by the tonal context. Implications of these findings for existing phonetic typology concerning tone-duration interaction are discussed.

Geographically well-distributed citizen science data reveals range-wide variation in the chipping sparrow's simple song

Geographical variation has been widely studied in oscine songbirds, with particular attention paid to the interplay between variables associated with learned song and dispersal. While most field-based studies have focused on discrete dialects, analysing data from quickly growing citizen science libraries could uncover geographical patterns in species previously thought to exhibit random variation in song. Specifically, using citizen science birdsong databases, we test whether chipping sparrow, Spizella passerina, song is geographically structured on a continental scale. The chipping sparrow is a particularly well-suited species for this study, since individuals have a simple song of one repeated syllable, have only the beginning of their first breeding season to adjust their song before crystallization and have been shown to match their song to a nearby neighbour while establishing their first territory. If most chipping sparrows adopt a neighbour-matching strategy, we might expect local syllable similarity; in contrast, field studies have shown that local syllable diversity has been maintained over time. We analyse 820 individual recordings of the simple, yet diverse, song of chipping sparrows to assess whether long-range geographical patterns have formed despite this local song variation. We found significant correlations between song features and geographical distance, associated with longitude but not latitude: chipping sparrows in the eastern United States and Canada sing at a slower rate (fewer, longer syllables) than the western population. However, comparing individual syllable types between regions, we found diverse song types persist across this species’ range. To better contextualize our findings, we re-evaluate available genetic sequences of chipping sparrows to test for genetic differentiation between the eastern and western populations in which we found song differences. Our results suggest that there are two culturally distinct subpopulations of migratory chipping sparrows that are genetically indistinguishable using mitochondrial DNA, motivating future studies on migration patterns and additional sequencing of nuclear DNA.

Context-dependent variation of house finch song syntax

We explored the role of social context in the syntactical variation of house finch, Haemorhous mexicanus, songs using both traditional song measures and network analysis. In comparison to solo bouts, the bouts of countersinging males had increased syntax diversity, with higher numbers of simple paths and transition types (but not syllable types) in comparison to solo song, which had high sequence consistency. Both the proportion of introductory syllables and the degree (number of transitions to and from those syllables) increased in countersinging bouts and were an important source of syntactic variability. In contrast, courtship bouts included longer songs and longer syllables than both solo and countersinging bouts, but were similar to solo songs in sequence consistency. The longest courtship songs often included concatenated sequences that formed ‘compound songs’, or repeating strings of main song syllables, which slightly increased the degree of those syllables. Our results suggest that interactions between males are associated with increased syntactic variability in song delivery while female choice favours signals that maintain species-typical syntax and demonstrate fitness in terms of a male's capacity to sing extended songs.

Effects of amygdala lesions on male mouse ultrasonic vocalizations and copulatory behaviour

Mice produce ultrasonic vocalizations (USVs) in several behavioural contexts. In particular, male mice articulate a long series of various sounds to females during courtship behaviour. To determine the relationships between this kind of vocal behaviour and emotion, we examined the lesion effects of the amygdala, an important neural module in emotional behaviour, on USVs. We recorded USVs from mice in the lesion and the control (sham operation) groups upon presentation of females and compared USVs before and after surgery. We found that the mean syllable duration of the USVs shortened and the appearance rate of longer syllables decreased after the surgery. The main reasons for these alterations could be explained by the altered courtship behaviour. As reported previously, the mounting behaviour of the lesion group after surgery was markedly less than that of the control group. Therefore, the appearance rate of those longer syllables would decrease logically because longer syllables primarily appear during mounting and intromission. However, we can hypothesize another scenario for the alterations to vocal behaviour: effects on the direct amygdala-periaqueductal grey (PAG) projection might be involved in the increase in the appearance rate of shorter syllables owing to lesion-induced loss of emotions, such as vigilance. Overall, the results suggested two possible mechanisms of the amygdala lesions on the alteration of the vocal behaviour.

Relative salience of acoustic features in zebra finch song.

Zebra finch song consists of complex acoustic elements repeated over several hundred milliseconds with extreme vocal-motor precision. Much less is known about how song is perceived though previous work has shown that zebra finches easily discriminate between normal and time-reversed versions of song syllables. Here, we used operant conditioning, psychophysical methods, and various synthetic song models to assess the bird’s sensitivity to local versus global temporal changes in song and to determine which cues are most salient in these complex syllables. Birds could discriminate syllable reversals in songs made up of the song envelope filled with noise, suggesting that syllable envelope cues can provide the basis for discrimination. However, birds could also discriminate syllable reversals in songs made up entirely of Schroeder harmonic complexes, stimuli that provide only phase (reversals of fine structure) cues without syllable envelope cues. Birds performed better on longer syllables, suggesting a window of temporal integration for fine structure discrimination. In contrast, humans could perceive few of the syllable reversals within these song modifications. This fine-grained perception in birds suggests that the machinery used for song perception is as precise as the machinery used for song production. [Work supported by NIH.]

Immune function reflected in calling song characteristics in a natural population of the cricket Teleogryllus commodus

Secondary sexual traits have been suggested to provide reliable signals of a male's ability to resist infection by agents of disease. The immunocompetence handicap hypothesis provides a potential mechanism for reliable signalling in the form of a trade-off between expenditure on trait expression and expenditure on immunity. Thus, males resistant to disease can spend more resources on their sexual signals. Examination of calling song parameters in a natural population of the cricket Teleogryllus commodus revealed that males scoring higher on the third principal component for song had significantly lower ability to encapsulate a foreign object. This component of immune function was associated with syllables of longer duration in both the trill and chirp elements of the song. Males with longer syllables in their song had a lower encapsulation ability. Syllable duration is known to influence phonotaxis by female T. commodus. Although the effect was only weak, our data suggest that females may base their choice of mate on reliable information contained within the temporal properties of male calls. Our study thus demonstrates a connection between sexual signalling and immune function in a natural population of insects and lends support to the immunocompetence handicap hypothesis.

Predators, risks and context for mobbing and alarm calls in black-billed magpies

Black-billed magpie, Pica pica hudsonia, mobbing and alarm calls were recorded for each of several different predator contexts. These were analysed spectrographically to determine whether the callers used temporal variation to communicate (1) the nature of the danger, (2) the identity of the predator and (3) the risks involved in actions resulting from alertness to the presence of the predator (e.g. fleeing or mobbing). The results support the notion that magpies vary call syllable length to give recipients information about the nature of the danger and to respond to a predator in an appropriate manner. Playback experiments were conducted using recordings of the separate call types as stimuli. The aim of the playback experiments was to determine whether one form of call elicits a more intense reaction from recipients than another call. It was found that magpies responded to calls with longer syllables by approaching the speaker while their response to calls with shorter syllables was aversive.