Perception of sequential structure in budgerigar (Melopsittacus undulatus) warble song.

The long, rambling warble song of male budgerigars is composed of a large number of acoustically complex elements uttered in streams lasting minutes a time and accompanied by various courtship behaviors. Warble song has no obvious sequential structure or patterned repetition of elements, raising questions as to which aspects of it are perceptually salient, whether budgerigars can detect changes in natural warble streams, and to what extent these capabilities are species-specific. Using operant conditioning and a psychophysical paradigm, we examined the sensitivity of budgerigars, canaries, and zebra finches to changes in long (>6min) natural warble sequences of a male budgerigar. All three species could detect a single insertion of pure tones, zebra finch song syllables, budgerigar contact calls, or warble elements from another budgerigar's warble. In each case, budgerigars were more sensitive to these changes than were canaries or finches. When warble elements from the ongoing warble stream were used as targets and inserted, out of order, into the natural warble stream so that the only cue available was the violation of the natural ordering of warble elements, only budgerigars performed above chance. When the experiment was repeated with all the ongoing warble stream elements presented in random order, the performance of budgerigars fell to chance. These results show species-specific advantages in budgerigars for detecting acoustic changes in natural warble sequences and indicate at least a limited sensitivity to sequential rules governing the structure of their species-specific warble songs.

The response of neurons of the budgerigar (Melopsittacus undulatus) was obtained in Field L, which is a laminated auditory structure of the caudal neostriatum in the telencephalon. Warble song of this species is comprised of a number of sounds (elements). The influence of sequence and silent intervals between elements on neuronal response was investigated. First, neurons in Field L were examined to know if neuronal response to isolated elements differed from that to the same elements in warble song, a sequence of elements. Sixty-two percent of the neurons exhibited increases of spike activity in response to elements in isolation compared with that to elements in warble song. These neurons thus exhibited temporally suppressed response. We then examined neuronal activity using the stimulation with paired elements, separated by various silent intervals (delta t msec). The spike activity in response to a specified element decreased as the interval was shortened. The responses of most neurons were strongly suppressed at the delta t of 80 msec, which is often seen in element intervals of warble song. In some neurons in Field L the response was suppressed, although they did not respond to the preceding sound. We hypothesize that temporally suppressed neurons may play a role in vocal discrimination.

The budgerigar (Melopsittacus undulatus) has an extraordinarily complex, learned, vocal repertoire consisting of both the long rambling warble song of males and a number of short calls produced by both sexes. In warble, the most common elements (>30%) bear a strong resemblance to the highly frequency-modulated, learned contact calls that the birds produce as single utterances. However, aside from this apparent similarity, little else is known about the relationship between contact calls and warble call elements. Here, both types of calls were recorded from four male budgerigars. Signal analysis and psychophysical testing procedures showed that the acoustic features of these two vocalizations were acoustically different and perceived as distinctive vocalizations by birds. This suggests that warble call elements are not simple insertions of contact calls but are most likely different acoustic elements, created de novo, and used solely in warble. Results show that, like contact calls, warble call elements contain information about signaler identity. The fact that contact calls and warble call elements are acoustically and perceptually distinct suggests that they probably represent two phonological systems in the budgerigar vocal repertoire, both of which arise by production learning.

In this study we present a preliminary analysis of the structure of the complex multisyllabic warble song of the budgerigar Melopsittacus undulatus, a small, flock-living parakeet. We recorded eight male budgerigars from three different social groups, and one female. Budgerigar warble songs consist in long sequences of syllables that are diverse in structure, ranging from simple clicks to multinote, frequency-modulated musical-sounding syllables. We identified 42 syllable classes. Males shared a significantly greater percentage of their warble syllable-class repertoire with males in the same social group than with males in different groups. One male budgerigar preferentially imitated the syllables and temporal pattern of the abnormal warble of his cagemate (a male bird that had been reared in acoustic and social isolation) rather than the normal warble of other male budgerigars in adjoining cages. We discuss vocal imitation of social companions as a process of vocal learning, the potential role o...

Effects of Lesions of the Central Nucleus of the Anterior Archistriatum on Contact Call and Warble Song Production in the Budgerigar (Melopsittacus undulatus)

Budgerigars are small Australian parrots that learn new vocalizations throughout adulthood. Earlier work has shown that an external acoustic model and auditory feedback are necessary for the development of normal contact calls in this species. Here, the role of auditory feedback in the maintenance of species-typical contact calls and warble song in adult budgerigars is documented. Deafened adult birds (five male, one female) vocalized less frequently and showed both suprasegmental and segmental changes in their contact calls and warble song. Contact calls of all adult-deafened budgerigars showed abnormalities in acoustic structure within days to a few weeks following surgery. Within 6 months of surgery, nearly all contact calls produced by deafened birds were strikingly abnormal, showing highly variable patterns of frequency modulation and duration. The warble song of deafened male budgerigars also differed significantly from that of normal budgerigars on several acoustic measures. These results show that auditory feedback is necessary for the maintenance of a normal, species-typical vocal repertoire in budgerigars.

Does audience affect the structure of warble song in budgerigars (Melopsittacus undulatus)?

The warble song of male budgerigars (Melopsittacus undulatus) is an extraordinarily complex, multisyllabic, learned vocalization that is produced continuously often for minutes at a time. Previous work has shown that warble elements form acoustic and perceptual categories for budgerigars and these birds can detect ordering changes in artificial sequences of warble elements. Using operant conditioning and a psychophysical paradigm, we examined the sensitivity of budgerigars for detecting different types of insertions (e.g., targets) in a running background of warble up 1000 elements in length. When the inserted targets are warble calls taken directly from the background, budgerigars show a species-specific ability to detect them solely based on sequence violations in the natural ordering of warble elements. Moreover, budgerigars, but not other species, are especially sensitive to temporally reversed warble elements inserted in natural warble sequences, indicating that the acoustic details of warble elements are also perceptually significant to budgerigars besides sequential cues. Although it is still unclear whether budgerigars perceive their warble as a rule-govern sequence or a pattern-based vocalization, the findings here open the door to studies of serial order learning in a natural, non-human communication system. [Work supported by NIH/NIDCD R01DC000198 to R.J.D.]

The warble songs of budgerigars (Melopsittacus undulatus) are composed of a number of complex, variable acoustic elements that are sung by male birds in intimate courtship contexts for periods lasting up to several minutes. If these variable acoustic elements can be assigned to distinct acoustic-perceptual categories, it provides the opportunity to explore whether birds are perceptually sensitive to the proportion or sequential combination of warble elements belonging to different categories. By the inspection of spectrograms and by listening to recordings, humans assigned the acoustic elements in budgerigar warble from several birds to eight broad, overlapping categories. A neural-network program was developed and trained on these warble elements to simulate human categorization. The classification reliability between human raters and between human raters and the neural network classifier was better than 80% both within and across birds. Using operant conditioning and a psychophysical task, budgerigars were tested on large sets of these elements from different acoustic categories and different individuals. The birds consistently showed high discriminability for pairs of warble elements drawn from between acoustic categories and low discriminability for pairs drawn from within acoustic categories. With warble elements reliably assigned to different acoustic categories by humans and birds, it affords the opportunity to ask questions about the ordering of elements in natural warble streams and the perceptual significance of this ordering.

The physical characteristics of vocalization were examined in budgerigars (Melopsittacus undulatus) deafened at the age of about 28 days. Autocorrelation was used in the analysis, with 2 parameters: 1) inter-element intervals and 2) amplitudes of all sound elements of the vocalization. The deafened birds developed the temporal pattern specific to normal warble song in autocorrelograms. However, abnormalities were found in the frequency spectrum of elements. The temporal pattern of warble song might be an innate character, because auditory feedback is unnecessary for its development.

Elaborate and colorful feathers are important traits in female mate choice in birds. Plumage coloration can result from pigments deposited in feathers such as carotenoids and melanins, or can be caused by nano‐scale reflective tissues (structurally based coloration), usually producing ultraviolet (UV) coloration. Structural colorations remain the least studied of the three most important feather colorations. Previous studies have found a female preference for UV color in the budgerigar, Melopsittacus undulatus, but it is not clear what information this ornament conveys, nor what is the possible cost associated with its production. We investigated possible correlations between immune response and plumage color of wild‐type (green) male budgerigars. In particular we measured the wing web swelling resulting from injection of phytohaemagglutinin (PHA). We did not detect any correlation between the sedimentation rate and morphological and color variables. We found that UV chroma is the best predictor for the cutaneous immune activity. Indeed, male budgerigars with high UV reflectance in the breast feathers showed stronger immune responses. These results are consistent with the idea that UV colors are special signals conveying information about a bird's condition.

Eight precopulatory behaviors were quantified for singly-caged, visually male and female Budgerigars that were castrated and/or given different dosages of testosterone progesterone, estradiol with or without progesterone or a placebo. Feminine soliciting for copulation seemed to be influenced mainly by blood estrogen levels, and not by other genetic and/or experiential factors associated with a feminine sexual identity. Estrogen and testosterone both stimulated to mount, but only in males. Of the remaining six typically precopulatory displays, no one factor seems to explain why, under typical breeding conditions, these precopulatory activities are observed to be performed mainly by male Budgerigars - to the extent that they have been denoted as behaviors. This study identifies three factors apart from the different and specific stimuli presented by a mate: (1) the presence of high levels of plasma gonadal hormones; (2) other genetic and/or experiential factors related to a sexual identity; and (3) an interaction of I and 2 whereby 2 prevents a greater responsiveness to hormonal stimuli. Data suggest that, when the varying and specific signals from a mate are disregarded, factor I may be most responsible for the masculine nature of Pumping and factor 2 for Bill-hooking and factor 3 for intention to mount and displays containing the nudging component, whereas those displays that also contain the Bill-hooking component seem to be associated with a baseline sexual difference and those displays that begin with Nudging followed by Pumping are stimulated by gonadal hormone levels. Thus, different interactions of hormonal and other factors associated with a sexual identity seem to influence the quantities of different precopulatory displays performed by isolated Budgerigars.

The budgerigar (Melopsittacus undulatus) is a promising model species for the study of adult vocal learning. To date, several studies have confirmed the existence of vocal plasticity and, more importantly, rapid imitation of contact calls by adult male budgerigars. Vocal learning has not been investigated in female budgerigars, however. Since one likely function of the contact call is to denote group affiliation, we tested the hypothesis that female budgerigars, when placed into groups, would develop a shared contact call. We recorded the contact call repertoires of eight adult female budgerigars that were unfamiliar with one another, then placed them into two groups. Each group was deprived of visual contact with other birds. Recording sessions continued for the subsequent 8 wks, and behavioral observations were also conducted during this time. Within 4–7 wks, females in both groups converged on a common call type. This rate of convergence is slower than that observed in prior experiments limited to male birds, and much slower than vocal imitation by male budgerigars paired with females. Therefore, while our study documents vocal plasticity in adult female budgerigars, it also suggests that female budgerigars learn new vocalizations more slowly than males do.

The soundgenerating mechanism in the bird syrinx has been the subject of debate. Recent endoscopic imaging of the syrinx during phonation provided evidence for vibrations of membranes and labia, bu...

Male budgerigars (Melopsittacus undulatus) are open-ended learners that can learn to produce new vocalisations as adults. We investigated neuronal activation in male budgerigars using the expression of the protein products of the immediate early genes zenk and c-fos in response to exposure to conspecific contact calls (CCs: that of the mate or an unfamiliar female) in three subregions (CMM, dNCM and vNCM) of the caudomedial pallium, a higher order auditory region. Significant positive correlations of Zenk expression were found between these subregions after exposure to mate CCs. In contrast, exposure to CCs of unfamiliar females produced no such correlations. These results suggest the presence of a CC-specific association among the subregions involved in auditory memory. The caudomedial pallium of the male budgerigar may have functional subdivisions that cooperate in the neuronal representation of auditory memory.