Cross-fostering diminishes song discrimination in zebra finches (Taeniopygia guttata)

Song-production, -discrimination, and -preferences in oscine birds are dually influenced by species identity and the ontogenetic environment. The cross-fostering of a model species for recognition research, the zebra finch (Taeniopygia guttata) into heterospecific nests of the Bengalese finch (Lonchura striata vars. domestica) allows an exploration of the sensory limits of early development and the effects of species-specific acoustic cues upon song discrimination in adulthood. To quantify the song preferences of female and male normal-reared (control) and Bengalese finch fostered zebra finches, we recorded multiple behavioral measures, including spatial proximity, vocalization rates and response latency, during sequential song-playback choice-trials using both tutor species’ songs and the songs of two other ecologically relevant Australian species, the owl finch (Taeniopygia bichenovii) and the star finch (Neochmia ruficauda). Response strength was variable between the different measures, but no differences were detected within the specific behavioral responses towards the song playbacks of the two sexes. Control subjects strongly preferred their own species’ songs while Bengalese-fostered zebra finches exhibited reduced song discrimination between con-, tutor-, and heterospecific songs. Overall behavioral responsiveness was also modulated by social ontogeny. These results indicate a difference in the strength of preference for song that is dependent on the species identity of the rearing environment in oscine birds and illustrate the role of multiple behavioral measures and ecologically relevant stimulus species selection in behavioral research using zebra finches.     

Rapidly learned song-discrimination without behavioral reinforcement in adult male zebra finches (Taeniopygia guttata)

Zebra finches communicate via several distinct vocalizations, of which song is the most studied. Behavioral observations indicate that adults are able to discriminate among the songs of different conspecific individuals. In the wild, zebra finches live in structured but mobile colonies, and encounter new individuals on a frequent basis. Thus it seems plausible that adult finches might have the capacity to recognize and remember new songs they encounter on a single day, but this has never been directly tested. Here we devised a simple observational assay to determine whether adult male zebra finches show recognition of a song they have heard repeatedly from taped playbacks, over a single three hour period the day before. We quantified the rate of production of six discrete behaviors (short calls, contact calls, singing, short hops, long hops, and beak swipes) made by adult male zebra finches as they listened to the playbacks. At the onset of song playback, all birds suspended these behaviors and sat silently-occasionally moving their heads. Then, after a measurable period ("response latency"), the birds resumed these activities. We observed that the response latency was long (approximately 10 min) when birds were hearing a particular song for the first time. The response latency was much shorter (approximately 1-2 min) when the birds had heard the same song the day before. Thus, functional song memories must result from as little as 3 h of passive song-exposure. These results suggest that ongoing song learning may play a natural role in the daily life of adult zebra finches, and provide a behavioral reference point for studies of molecular and physiological plasticity in the adult auditory system.     

Song perception during the sensitive period of song learning in zebra finches (Taeniopygia guttata)

The sensitive period is a special time for auditory learning in songbirds. However, little is known about perception and discrimination of song during this period of development. The authors used a go/no-go operant task to compare discrimination of conspecific song from reversed song in juvenile and adult zebra finches (Taeniopygia guttata), and to test for possible developmental changes in perception of syllable structure and syllable syntax. In Experiment 1, there were no age or sex differences in the ability to learn the discrimination, and the birds discriminated the forward from reversed song primarily on the basis of local syllable structure. Similar results were found in Experiment 2 with juvenile birds reared in isolation from song. Experiment 3 found that juvenile zebra finches could discriminate songs on the basis of syllable order alone, although this discrimination was more difficult than one based on syllable structure. The results reveal well-developed song discrimination and song perception in juvenile zebra finches, even in birds with little experience with song.     

Effects of humidity on reproductive behavior in male and female zebra finches (Taeniopygia guttata).

Zebra finches (Taeniopygia guttata) are regarded as opportunistic breeders with reproductive behaviors mediated by short-term proximal environmental conditions. This article provides experimental evidence for the role of humidity in reproductive behaviors. Zebra finches were subjected to experimentally manipulated high levels of relative humidity. Males gathered more nest material and sang more. Females showed no relationship between humidity and gathering nest materials, egg laying, or changes in rates of vocalization.     

Timbre control in zebra finch (Taeniopygia guttata) song syllables

Zebra finch (Taeniopygia guttata) song syllables often include harmonically related frequency components. These harmonics may be suppressed, and this differential emphasis varies between the syllables in a song and between individual birds' songs. These patterns of harmonic suppression are timbre. Individual syllables' patterns of harmonic suppression are constant with adult males' songs. Young males that imitate the songs of older males also imitate their patterns of harmonic suppression. Syringeal denervation distorts these patterns, which suggests that they are produced through active control of the vocal organ. The selective suppression and emphasis of some harmonics creates a great number of possible timbre variants for any one syllable. These add signal diversity to the limited array of frequency modulations and range of fundamental frequencies found in zebra finch song. Analyses of bird song that disregard timbre may overlook a feature that is important in vocal communication.     

Syllable chunking in zebra finch (Taeniopygia guttata) song.

We examined how 61 young zebra finch (Taeniopygia guttata) males copied song from 5 adult tutors. Zebra finch song consists of a string of 5-15 distinct syllables, and these syllables were copied as chunks, or strings of consecutive syllables (modal length = 3). The silent interval between 2 syllables was copied as part of the syllable after the silence. Copied chunks had boundaries that fell at consistent locations within the tutor's song, marked by a relatively long intersyllable silent period, a transition between call-like and noncall-like syllables, and a tendency for the tutor male to stop his song short. Young males also tended to break their songs off at the boundaries of the chunks they had copied. Chunks appear to be an intermediate level of hierarchy in song organization and to have both perceptual (syllables were learned as part of a chunk) and motor (song delivery was broken almost exclusively at chunk boundaries) aspects.     

Timbre discrimination in zebra finch (Taeniopygia guttata) song syllables

Zebra finch (Taeniopygia guttata) songs include syllables of a fundamental frequency and harmonics. Individual harmonics in 1 syllable can be more or less emphasized. The functional role of this variability is unknown. These experiments provide evidence of how the phenomenon is perceived. We trained 12 male and female zebra finches on a go-no-go operant procedure to discriminate between 2 song syllables that varied only in the absence of the 2nd or 5th harmonic. Training involved many thousands of trials. Both sexes used the presence or absence of the 2nd harmonic as the sole discriminative cue. Females had more difficulty learning to perform the task when the presence of the 2nd harmonic was the go stimulus, which indicates that their use of the information was biased by stimulus-response contingencies. The results are discussed in terms of a broad strategy to understand how animals perceive sounds used in communication.     

Breeding cycle aggression in domesticated zebra finches (Poephila guttata)

Patterns of breeding cycle aggressive behavior were examined in colonies of domesticated zebra finches (Poephila guttata). Aggressive behaviors of zebra finch pairs were low during non-nesting periods but were maintained at high levels during the three nesting periods: the incubating, hatching, and nestling periods. Defense of the nest site was the prominent functional category of aggression, followed by defense of individual distance. Defense of mate, defense of young, and defense of nesting material rarely occurred. Male and female members of pair bonds shared the duties of defense of the nest site and parental care. During observation times males exhibited greater frequencies of aggressive actions throughout the breeding cycle and females spent a greater amount of time in the nest during the three nesting periods. The pattern and functional categories of aggressive behavior in the zebra finch colonies correspond most closely to the nest site defense hypothesis for the evolution of breeding season aggression.     

Perception of distance calls by budgerigars (Melopsittacus undulatus) and zebra finches (Poephila guttata): assessing species-specific advantages

Budgerigars (Melopsittacus undulatus) and zebra finches (Poephila guttata) share a common functional class of vocalizations called distance calls. The perception of species-specific distance calls by both species was measured with a habituation-dishabituation operant paradigm. Changes in discrimination performance were noted as listening conditions were modified or stimulus properties were altered. Both species showed better performance for calls of their own species. For zebra finches this tendency increased slightly when a background noise was added to the testing environment. Shifting the frequency region of the calls affected the discrimination performance of male budgerigars but not females or zebra finches. Reversing the temporal order of the calls affected the perceptual advantage for conspecific vocalizations in zebra finches but not in budgerigars. These results highlight species differences in perceiving acoustic communication signals.     

Absolute pitch: frequency-range discriminations in pigeons (Columba livia): comparisons with zebra finches (Taeniopygia guttata) and humans (Homo sapiens)

Absolute pitch (AP) is the ability to classify individual pitches without an external referent. The authors compared results from pigeons (Columba livia, a nonsongbird species) with results (R. Weisman, M. Njegovan, C. Sturdy, L. Phillmore, J. Coyle, & D. Mewhort, 1998) from zebra finches (Taeniopygia guttata, a songbird species) and humans (Homo sapiens) in AP tests that required classification of contiguous tones into 3 or 8 frequency ranges on the basis of correlations between the tones in each frequency range and reward. Pigeons' 3-range discriminations were similar in accuracy to those of zebra finches and humans. In the more challenging 8-range task, pigeons, like zebra finches, discriminated shifts from reward to nonreward from range to range across all 8 ranges, whereas humans discriminated only the 1st and last ranges. Taken together with previous research, the present experiments suggest that birds may have more accurate AP than mammals.     

Frequency-range discriminations and absolute pitch in black-capped chickadees (Poecile atricapillus), mountain chickadees (Poecile gambeli), and zebra finches (Taeniopygia guttata)

The acoustic frequency ranges in birdsongs provide important absolute pitch cues for the recognition of conspecifics. Black-capped chickadees (Poecile atricapillus), mountain chickadees (Poecile gambeli), and zebra finches (Taeniopygia guttata) were trained to sort tones contiguous in frequency into 8 ranges on the basis of associations between response to the tones in each range and reward. All 3 species acquired accurate frequency-range discriminations, but zebra finches acquired the discrimination in fewer trials and to a higher standard than black-capped or mountain chickadees, which did not differ appreciably in the discrimination. Chickadees' relatively poorer accuracy was traced to poorer discrimination of tones in the higher frequency ranges. During transfer tests, the discrimination generalized to novel tones when the training tones were included, but not when they were omitted.     

Hippocampal activation of immediate early genes Zenk and c-Fos in zebra finches (Taeniopygia guttata) during learning and recall of a spatial memory task

Zebra finches (Taeniopygia guttata) are able to learn the position of food by orienting on spatial cues in a ‘dry water maze’. In the course of spatial learning, the hippocampus shows high expression of the immediate early genes (IEGs) Zenk and c-Fos, indicating high activation of this area during learning. In contrast, the IEG activity is nearly absent if the birds do not have to rely on spatial cues. In the present experiment it was investigated whether hippocampal activation can also be observed if the learned spatial task is recalled. For this purpose, the hippocampal Zenk and c-Fos activation of birds in an early learning stage was compared with that of others having well reached their maximal performance. The results show that the avian hippocampus is also active during recall of a learned spatial task, but the activation is significantly lower than in animals learning actually. As in previous experiments, hippocampal IEG expression showed strong variation not only in the position of the active patches of neurons, but also in size and cell density. The observed difference contributes to the view that immediate early genes may not be indicators of activation alone, but may be due to a combination of activation and plastic changes.     

Experimental determination of a unit of song production in the zebra finch (Taeniopygia guttata)

Zebra finch (Taeniopygia guttata) song is composed of syllables delivered in a set order. Little is known about the program that controls this temporal delivery. A decision to sing or not to sing may or may not affect the entire song. Song, once commenced, may continue or may halt. If song is halted, stops may occur only at certain points. Seven zebra finches were presented with short bursts of strobe light while engaged in song. The variables of interest were whether the birds stopped and where they stopped. The results can be summarized as follows: Ongoing zebra finch song can be interrupted, interruptions occur at discrete locations in song, and the locations almost always fall between song syllables. These results reveal a functional representation of song production and place constraints on possible neural mechanisms that underlie song production in zebra finches and probably other oscine species. The results also raise hypotheses about the elements of song perception and memory.     

Zebra finches (Taeniopygia guttata) demonstrate cognitive flexibility in using phonology and sequence of syllables in auditory discrimination

Animal Cognition - Zebra finches rely mainly on syllable phonology rather than on syllable sequence when they discriminate between two songs. However, they can also learn to discriminate two...     

Auditory scene analysis in estrildid finches (Taeniopygia guttata and Lonchura striata domestica): a species advantage for detection of conspecific song

Operant-conditioning techniques were used to investigate the ability of zebra finches (Taeniopygia guttata) and Bengalese finches (Lonchura striata domestica) to detect a zebra finch or a Bengalese finch target song intermixed with other birdsongs. Sixteen birds were trained to respond to the presence of a particular target song, either of their own species (n = 8) or of another species (n = 8). The birds were able to learn a discrimination between song mixtures that contained a target song and song mixtures that did not, and they were able to maintain their response to the target song when it was mixed with novel songs. Zebra finches, but not Bengalese finches, learned the discrimination with a conspecific target more quickly and were worse at detecting a Bengalese finch in the presence of a conspecific song. The results indicate that selective attention to birdsongs within an auditory scene is related to their biological relevance.     

The precedence effect in three species of birds (Melopsittacus undulatus, Serinus canaria, and Taeniopygia guttata)

The perceived locations of paired auditory images, simulating direct sounds and their echoes, have been recently studied in budgerigars (Melopsittacus undulatus; M. L. Dent & R. J. Dooling, 2003a, 2003b). In this article, the authors extend those experiments to include measurements of the precedence effect using a discrimination paradigm in two additional bird species: canaries (Serinus canaria) and zebra finches (Taeniopygia guttata). Although time courses of summing localization, localization dominance, and echo thresholds were similar across all species, budgerigars had slightly higher overall levels of discrimination. The results from these experiments add further support that the precedence effect in birds is similar to that found in other animals and that the ability to suppress echoes that might degrade localization and auditory object perception may be a general property of the vertebrate auditory system.     

The vocal repertoire of the domesticated zebra finch: a data-driven approach to decipher the information-bearing acoustic features of communication signals

Although a universal code for the acoustic features of animal vocal communication calls may not exist, the thorough analysis of the distinctive acoustical features of vocalization categories is important not only to decipher the acoustical code for a specific species but also to understand the evolution of communication signals and the mechanisms used to produce and understand them. Here, we recorded more than 8000 examples of almost all the vocalizations of the domesticated zebra finch, Taeniopygia guttata: vocalizations produced to establish contact, to form and maintain pair bonds, to sound an alarm, to communicate distress or to advertise hunger or aggressive intents. We characterized each vocalization type using complete representations that avoided any a priori assumptions on the acoustic code, as well as classical bioacoustics measures that could provide more intuitive interpretations. We then used these acoustical features to rigorously determine the potential information-bearing acoustical features for each vocalization type using both a novel regularized classifier and an unsupervised clustering algorithm. Vocalization categories are discriminated by the shape of their frequency spectrum and by their pitch saliency (noisy to tonal vocalizations) but not particularly by their fundamental frequency. Notably, the spectral shape of zebra finch vocalizations contains peaks or formants that vary systematically across categories and that would be generated by active control of both the vocal organ (source) and the upper vocal tract (filter).     

Motivation and memory in zebra finch (<Emphasis Type="Italic">Taeniopygia guttata</Emphasis>) foraging behavior

Remembering combinations of information such as what resources have been seen in which locations could play an important role in enhancing individual survival through increased foraging success. To date, there have been relatively few investigations of avian memory involving more than one category of information. This study explored zebra finches’ (Taeniopygia guttata) capacity to recall two categories in combination, namely food-type and spatial location. Birds were trained to remove variously weighted flaps to find two types of food hidden beneath. Memory for food-types and locations was assessed by pre-feeding the birds to satiety on and devaluing one food-type, and then testing the birds’ efficiency at finding the non-devalued food. When allowed one trial to learn locations of two food rewards that were hidden beneath lightly weighted flaps, birds performed better than chance at locating a food reward. However, they did not preferentially search for the non pre-fed food, suggesting that they were unable to recall both food type and location in combination. Zebra finches made fewer errors when tested on the one-trial task using more heavily weighted flaps than with lightly weighted flaps; there was equivocal evidence that they remembered which food type was hidden where on this task. When given repeated exposures to the locations of the two food rewards, finches located a food reward more accurately than on the one-trial tasks, and were also more likely to recall the locations of the different food types. In this foraging paradigm, experience and motivation may have influenced the birds’ performance.     

Perceptual organization of acoustic stimuli by budgerigars (Melopsittacus undulatus): III. Contact calls

We trained budgerigars by operant conditioning to discriminate among a set of contact calls in a same-different task and analyzed response latencies from this task by using multidimensional-scaling (MDS) and cluster-analysis procedures. Humans listened to the same calls and indicated the similarity between pairs of calls by a direct rating procedure. An MDS program (sindscal) was used to arrange these complex acoustic stimuli in multidimensional space reflecting perceptual organization. Multiple regression techniques were used to identify the acoustic characteristics of contact calls that were correlated with the perceptual dimensions obtained from MDS. A number of spectral characteristics (e.g., peak frequency, rate of frequency modulation, and concentration of spectral energy) emerged as important for both budgerigars and humans, but the relative salience of these cues differed for the two species. Additional tests with two groups of budgerigars--cagemates and noncagemates--showed that experience with calls can change the salience of various acoustic characteristics used for perceptual organization and individual recognition.