Conspecific Song Recognition Research Articles

Asymmetric song responses in coexisting Japanese cicadas

Diel partitioning of singing, which has been observed from the tropics to the temperate regions, is among the various mechanisms of sound partitioning found in multispecies cicada assemblages and is regarded as an important mechanism of coexistence. Using playback experiments, we studied interspecific interference between two Japanese cicadas, Cryptotympana facialis and Graptopsaltria nigrofuscata, which exhibit similar peak frequencies in their calling songs and different diel patterns of song activity. We found that the males of the two species had different song response patterns: C. facialis responded significantly more to conspecific calling songs than G. nigrofuscata. These results suggest that male C. facialis have evolved more intense conspecific song recognition than G. nigrofuscata. This may cause male G. nigrofuscata to avoid destructive acoustic interference during their active singing time.

Active recognition enhances the representation of behaviorally relevant information in single auditory forebrain neurons

Sensory systems are dynamic. They must process a wide range of natural signals that facilitate adaptive behaviors in a manner that depends on an organism's constantly changing goals. A full understanding of the sensory physiology that underlies adaptive natural behaviors must therefore account for the activity of sensory systems in light of these behavioral goals. Here we present a novel technique that combines in vivo electrophysiological recording from awake, freely moving songbirds with operant conditioning techniques that allow control over birds' recognition of conspecific song, a widespread natural behavior in songbirds. We show that engaging in a vocal recognition task alters the response properties of neurons in the caudal mesopallium (CM), an avian analog of mammalian auditory cortex, in European starlings. Compared with awake, passive listening, active engagement of subjects in an auditory recognition task results in neurons responding to fewer song stimuli and a decrease in the trial-to-trial variability in their driven firing rates. Mean firing rates also change during active recognition, but not uniformly. Relative to nonengaged listening, active recognition causes increases in the driven firing rates in some neurons, decreases in other neurons, and stimulus-specific changes in other neurons. These changes lead to both an increase in stimulus selectivity and an increase in the information conveyed by the neurons about the animals' behavioral task. This study demonstrates the behavioral dependence of neural responses in the avian auditory forebrain and introduces the starling as a model for real-time monitoring of task-related neural processing of complex auditory objects.

Pitch-related cues in the songs of sympatric mountain and black-capped chickadees

Acoustic frequency (pitch) cues are known to be important in the recognition of conspecific song in a number of songbird species. Mountain chickadees (Poecile gambeli) and black-capped chickadees (Poecile atricapillus) are sympatric over parts of their ranges and their species-typical songs share many features. I examined the acoustic characteristics of song of these two congeners in a region of sympatry in southern Alberta, Canada. As reported for other populations in allopatry, black-capped chickadees emphasized relative frequency cues in song production. In particular, variation in the ratios between note frequencies was significantly less than variation in the note frequencies themselves. In contrast, songs of mountain chickadees did not have constant frequency ratios and contained an introductory acoustic element absent in black-capped chickadee song. Both species may rely on song note frequency or the presence of this introductory acoustic element when differentiating between conspecific song and heterospecific song. Song measures for chickadees in sympatry were similar to measures in allopatry, providing little evidence for character displacement in song production.

Acoustic pattern recognition in a grasshopper: processing in the time or frequency domain?

Males of the grasshopper Chorthippus biguttulus produce songs which consist of the stereotyped and rhythmic iteration of a sound unit (termed syllable) separated by distinct syllable pauses. Virgin females respond to this signal, and to similar artificial signals, with song phrases of their own. In behavioural experiments the response probability of virgin females can be measured with artificial acoustic stimuli. The stimuli consisted of an amplitude modulated noise the envelope of which was altered. We investigated several hypotheses on the mechanisms of conspecific song recognition with special emphasis on the question whether recognition occurs in the frequency domain or in the time domain. (1) Females of Ch. biguttulus required only the first five Fourier components of the envelope function (corresponding to 50 Hz for a fundamental frequency of 10 Hz) to detect the syllable/pause structure. In addition, they detected small gaps within syllables if the signal contained at least ca. 15 Fourier components (corresponding to a frequency of 150 Hz). Further experiments showed that the correct phase information of the Fourier components is necessary for recognition, indicating that pattern recognition is not achieved merely on the basis of band pass filtering. (2) A cross correlation between the signal and an assumed internal template yields only inconsistent predictions of the response probabilities. (3) The recognizer system probably works in the time domain, possibly by direct comparison of adjacent syllable and pause durations. It is not yet clear whether the duration of a syllable is evaluated with respect to the preceding or succeeding pause. We emphasize that the neural recognizer of the grasshopper does not only examine a signal for its similarity to an internal template, but that it also takes into account features that indicate an incorrect signal. This may be a general feature of neuronal pattern recognition systems which have been shaped by natural selection.

A Field Test of the Sound Environment Hypothesis of Conspecific Song Recognition in American Tree Sparrows (Spizella Arborea)

Abstract The sound environment hypothesis predicts that the features of song that are important for conspecific recognition should be those that overlap least with the songs of other species in the same location. We tested this hypothesis with song playbacks to free-living male American tree sparrows (Spizella arborea). We first used a discriminant function analysis to determine which song features best separated American tree sparrow songs from the songs of heterospecific avian species at two locations representing different sound environments. Based on this analysis we predicted which song features should be most important for conspecific recognition at each location. We then produced synthetic songs containing alterations in these features. Males, however, did not respond to playbacks of altered features as predicted. Thus, our results do not support the sound environment hypothesis of conspecific song recognition.

Nerve Cells and Insect Behavior—Studies on Crickets

Intraspecific acoustic communication during pair formation in crickets provides excellent material for neuroethological research. It permits analysis of a distinct behavior at its neuronal level. This top-down approach considers first the behavior in quantitative terms, then searches for its computational rules (algorithms), and finally for neuronal implementations. The research described involves high resolution behavioral measurements, extra- and intracellular recordings, and marking and photoinactivation of single nerve cells. The research focuses on sound production in male and phonotactic behavior in female crickets and its underlying neuronal basis. Segmental and plurisegmental organization within the nervous system are examined as well as the validity of the single identified neuron approach. Neuroethological concepts such as central pattern generation, feedback control, command neuron, and in particular, cellular correlates for sign stimuli used in conspecific song recognition and sound source localization are discussed. Crickets are ideal insects for analyzing behavioral plasticity and the contributing nerve cells. This research continues and extends the pioneering studies of the late Kenneth David Roeder on nerve cells and insect behavior by developing new techniques in behavioral and single cell analysis.

Absolute and relative pitch processing in black-capped chickadees, Parus atricapillus

Playback studies have often identified note order as a feature in the recognition of conspecific song by passerines. Pitch change between successive notes in song could be an important source of order features. In two experiments, we varied the absolute and relative pitch in conspecific fee bee songs played to captive male black-capped chickadees. In experiment 1, songs beginning appreciably higher or lower in absolute pitch than normal song elicited less social response. In experiment 2, songs played at altered pitch intervals tended to elicit less combined agonistic and territorial response. These experiments indicate that chickadees are sensitive to both absolute and relative pitch information present in conspecific song.

Sexual display response of female white-crowned sparrows to normal, isolate and modified conspecific songs

Female white-crowned sparrows, Zonotrichia leucophrys, were tested for their sexual display response to several song stimuli. Experiment 1 showed that subjects displayed more to normal conspecific song than to normal song of the song sparrow, Melospiza melodia, a co-occurring and closely related species. Experiment 2 showed that subjects did not respond differently to isolate conspecific song and isolate song sparrow song; response to these stimuli was low in general. The results of experiment 2 implied that isolate song did not contain sufficient information for conspecific song recognition by females. Experiment 3 tested female response to songs composed of both normal and isolate components. The general trend was that the number of female displays increased with the number of normal components substituted for isolate song components, but one particular component of normal song, the ‘simple syllables’, appeared to elicit a large increase in female displays and thus may serve an important function in the recognition of conspecific song by female white-crowned sparrows.

Recognition of conspecific song by the rufous-sided towhee

Dual-speaker experiments conducted with rufous-sided towhees ( Pipilo erythrophthalmus) demonstrated that they do not respond to song of three other species and that the sequence and diversity of phrases within a song, and the time interval between syllables of the note-complex phrase, may be important in species recognition. These results are compared with results of song recognition studies done with species that are extensively sympatric with towhees in eastern North America.

The responses of ventral cord neurons of Decticus verrucivorus (L) to sound and vibration stimuli

The real time analysis of the song of D. verrucivorus recorded in the sun and shade shows that changes occur predominantly in the time parameters and not in the frequency content. Single unit recordings in the ventral nerve cord of D. verrucivorus show that all the acoustic units respond to both sound and vibration. However, on the basis of their response characteristics they may be classified as vibration (V), vibration and sound (VS) and sound (S) neurons. The responses of some of the units depend upon the degree of habituation. Single parameter processing was not observed; the characteristic frequencies of these units range across the whole of the frequency band investigated, and distinct intensity response fields were observed. Some of the V neurons were more sensitive than the receptors, and some units responded well to the species song when both sound and vibration were presented simultaneously. The source of the vibratory input is shown to be predominantly from the ipsilateral foreleg. Many of the units run together in an ‘acoustic bundle’; some run through fibres, passing from the posterior thoracic ganglia to the cervical connectives. In many cases the primary fibres projecting to these central units can be predicted from their response characteristics. An hypothesis of the mechanisms underlying conspecific song recognition at the ventral cord level is presented.