Song organisation and patterns of variation in the serin (Serinus serinus)

This article describes the organisation of song in the serin (Serinus serinus) and analyses its variation among individuals. Serins have a repertoire of about 50 complex syllables that are sung at a very fast rate and in a very stereotyped order, forming discrete songs. Songs are high pitched for the serin’s body size. Song organisation is circular, with a limited number of starting points. Songs can stop at any point in their cycling. Within songs there are trilled sections and fast, non-repeated sections that account for the greatest part of songs. These two modes of singing also differ in average inter-element intervals and probably in their respiratory kinematics. Bird repertoire size was measured and the difficulties of measuring it in this species are discussed. Repertoires are individually specific and have a variable amount of syllable sharing with other birds. We found evidence for geographical variation in the composition of repertoires. Considering our current knowledge of song in carduelines, the stereotyped and circular nature of serin song appear to be unique within this group of birds. Received: 30 May 2000 / Received in revised from: 14 August 2000 / Accepted: 12 September 2000     

Complex modulation of singing behavior by testosterone in an open-ended learner, the European Starling

In many temperate zone songbird species males only produce song during the breeding season, when plasma testosterone (T) levels are high. Males of some species sing throughout the year, even when T levels are low, indicating a dissociation between high T levels and song rate. Given that few studies have taken advantage of these species, we compare here song traits expressed under high versus low T concentrations and we study the role of testosterone in adult song learning in the European Starling, an open-ended learner in which repertoire size dramatically increases with age. We performed a detailed comparison of song complexity and song rate between fall and spring in 6-year-old intact male European starlings. In parallel, we investigated whether potential seasonal changes were regulated by the gonadally induced increase in plasma T, by comparing seasonal changes in intact and castrated males of the same age (castrated as juveniles during their first fall) and by subsequently experimentally elevating T in half of the castrated males. While song rate and stereotypy did not differ between intacts and castrates or between fall and spring, both groups increased their average song bout length from fall to spring, but only intact males increased their repertoire size, indicating that effects of seasonal T changes differ between song traits. Intact males overall displayed a larger song repertoire and a longer bout length than the castrates, and implantation with T caused a turnover in repertoire composition in castrates. However, as the castrates had never experienced high T levels and yet displayed a markedly higher repertoire size than that of typical yearling males, this suggests that the progressive increase of song repertoire with age in male starlings is not dependent on gonadal T, although it may be T-enhanced.     

Use of fragment–sharing estimates from DNA fingerprinting to determine relatedness in a tropical wren

We assessed the usefulness of DNA fragment–sharing scores from DNA fingerprints for assigning relatedness to unknown pairs of individuals in a population of stripe–backed wrens (Campylorhynchus nuchalis). Preliminary investigation of scoring biases revealed consistency both within and between scorers in relative band–sharing scores, but a tendency for scores to be inflated and for inter–scorer agreement to decline as distance between lanes on an autoradiograph increased. Distributions of band–sharing values matched expected distributions well, which suggests that variability in scores is mostly inherent and not a result of errors in scoring. Confidence intervals based on band–sharing scores or means of scores across enzymes, probes and scorers revealed that unrelated (r= 0) and first–order dyads (r=Vi) could be distinguished on the basis of single band–sharing scores from the best combination of enzyme and probe (HaeIII/33.15) and that first– and second–order dyads could be distinguished when confidence intervals were based on means of band–sharing scores across two enzymes, two probes and two scorers.     

Effects of learning on song preferences and Zenk expression in female songbirds

Male songbirds learn to produce their songs, and females attend to these songs during mate choice. The evidence that female song preferences are learned early in life, however, is mixed. Here we review studies that have found effects of early song learning on adult song preferences, and those that have not. In at least some species, early experience with song can modify adult song preferences. Whether this learning needs to occur during an early sensitive phase, akin to male imitative vocal learning, or not remains an open question. Studies of the neural bases for female song preferences highlight activity (as measured by immediate-early gene induction) in regions of the auditory forebrain as often, but not always, being associated with song preferences. Immediate-early gene induction in these regions, however, is not specific to songs experienced early in life. On the whole, inherited factors, early experience, and adult experience all appear to play a role in shaping female songbirds preferences for male songs.     

Song pattern recognition and an auditory time window in the female bushcricket Ancistrura nigrovittata (Orthoptera: Phaneropteridae)

Mate finding in the phaneropterid bushcricket Ancistrura nigrovittata is achieved by a duet, where the female replies with a short sound to the male song. In experiments with artificial song models we analysed the parameters necessary for eliciting a female response. A verse of the male song consists of a group of 5–9 syllabes which after an interval of about 400 ms is followed by a final syllable. The female response was shown to depend on two processes: (i) recognition of the syllable group as belonging to a conspecific male and (ii) perception of the final syllable as a trigger. Critical parameters for the recognition process are the duration of syllables and syllable pauses, as well as the number of syllables in a group. However, even with an optimal syllable group, the response probability still depends on the interval between the syllable group and the final syllable. The female only responds when the final syllable of the male song occurs within a 250 ms long time window begining approximately 250 ms after the end of the male's syllable group. Her reply consists of a single tick, which follows the male's final syllable with a latency of only 25 ms.     

Species differences in the identification of acoustic stimuli by birds

The perceptual organization of auditory stimuli can reveal a great deal about how the brain naturally groups events. The current study uses identification techniques to investigate the abilities of two species of birds in identifying zebra finch song as well as synthetically generated speech stimuli. Budgerigars (Melopsittacus undulatus) and zebra finches (Taeniopygia guttata) were trained to differentially peck keys in response to the presentation of various complex stimuli. Although there were no clear differences in performance during the training paradigm between the two species, budgerigars were far more adept at learning to identify both sets of complex stimuli than were zebra finches, requiring far less trials to reach criterion. The non-singing but vocally plastic budgerigars vastly outperformed zebra finches at identifying both zebra finch song and synthetically designed human speech despite known similarities in auditory sensitivities between the two species and seemingly equivalent learning capacity. The flexibility that budgerigars seem to have at identifying various stimuli is highlighted by their enhanced performance in these tasks. These results are discussed in the context of what is known about both general and specialized processes which may contribute to any differences or similarities in performance.     

Sex-biased terminal investment in offspring induced by maternal immune challenge in the house wren (Troglodytes aedon)

The reproductive costs associated with the upregulation of immunity have been well-documented and constitute a fundamental trade-off between reproduction and self-maintenance. However, recent experimental work suggests that parents may increase their reproductive effort following immunostimulation as a form of terminal parental investment as prospects for future reproduction decline. We tested the trade-off and terminal investment hypotheses in a wild population of house wrens (Troglodytes aedon) by challenging the immune system of breeding females with lipopolysaccharide, a potent but non-lethal antigen. Immunized females showed no evidence of reproductive costs; instead, they produced offspring of higher phenotypic quality, but in a sex-specific manner. Relative to control offspring, sons of immunized females had increased body mass and their sisters exhibited higher cutaneous immune responsiveness to phytohaemagglutinin injection, constituting an adaptive strategy of sex-biased allocation by immune-challenged females to enhance the reproductive value of their offspring. Thus, our results are consistent with the terminal investment hypothesis, and suggest that maternal immunization can induce pronounced transgenerational effects on offspring phenotypes.     

Song environment affects singing effort and vasotocin immunoreactivity in the forebrain of male Lincoln's sparrows

Male songbirds often establish territories and attract mates by singing, and some song features can reflect the singer's condition or quality. The quality of the song environment can change, so male songbirds should benefit from assessing the competitiveness of the song environment and appropriately adjusting their own singing behavior and the neural substrates by which song is controlled. In a wide range of taxa, social modulation of behavior is partly mediated by the arginine vasopressin or vasotocin (AVP/AVT) systems. To examine the modulation of singing behavior in response to the quality of the song environment, we compared the song output of laboratory-housed male Lincoln's sparrows (Melospiza lincolnii) exposed to 1 week of chronic playback of songs categorized as either high or low quality, based on song length, complexity, and trill performance. To explore the neural basis of any facultative shifts in behavior, we also quantified the subjects' AVT immunoreactivity (AVT-IR) in three forebrain regions that regulate sociosexual behavior: the medial bed nucleus of the stria terminalis (BSTm), the lateral septum (LS), and the preoptic area. We found that high-quality songs increased singing effort and reduced AVT-IR in the BSTm and LS, relative to low-quality songs. The effect of the quality of the song environment on both singing effort and forebrain AVT-IR raises the hypothesis that AVT within these brain regions plays a role in the modulation of behavior in response to competition that individual males may assess from the prevailing song environment.     

Diversity in sound pressure levels and estimated active space of resident killer whale vocalizations

Signal source intensity and detection range, which integrates source intensity with propagation loss, background noise and receiver hearing abilities, are important characteristics of communication signals. Apparent source levels were calculated for 819 pulsed calls and 24 whistles produced by free-ranging resident killer whales by triangulating the angles-of-arrival of sounds on two beamforming arrays towed in series. Levels in the 1–20 kHz band ranged from 131 to 168 dB re 1 μPa at 1 m, with differences in the means of different sound classes (whistles: 140.2±4.1 dB; variable calls: 146.6±6.6 dB; stereotyped calls: 152.6±5.9 dB), and among stereotyped call types. Repertoire diversity carried through to estimates of active space, with “long-range” stereotyped calls all containing overlapping, independently-modulated high-frequency components (mean estimated active space of 10–16 km in sea state zero) and “short-range” sounds (5–9 km) included all stereotyped calls without a high-frequency component, whistles, and variable calls. Short-range sounds are reported to be more common during social and resting behaviors, while long-range stereotyped calls predominate in dispersed travel and foraging behaviors. These results suggest that variability in sound pressure levels may reflect diverse social and ecological functions of the acoustic repertoire of killer whales.     

Song matching, overlapping, and switching in the banded wren: the sender's perspective

Interpreting receiver responses to on-territory playback ofaggressive signals is problematic. One solution is to combinesuch receiver-perspective experiments with a sender-perspectiveexperiment that allows subjects to demonstrate how their choiceof singing strategies is associated with their approach behavior.Here we report the results of a sender-perspective study onthe banded wren (Thryothorus pleurostictus) and combine informationon context and results of previous receiver-perspective experimentsto clarify function. Territorial males were presented with a5-min playback consisting of song types present in their repertoire.We assessed the degree to which the subjects' song-matchingrate, overlapping rate, and song-type versatility were correlatedwith their approach latency, closeness of approach, latencyto first retreat, and time spent close to the speaker. Maleage, breeding stage, and features of the playback stimuli werealso considered. Song matching was associated with rapid andclose approach, consistent with the receiver-perspective interpretationof type matching as a conventional signal of aggressive motivation.Overlapping was associated with earlier retreat and togetherwith the aversive receiver response to our previous overlappingplayback experiment suggests that overlapping is a defensivewithdrawal signal. High versatility was associated with slowerfirst retreat from the speaker and high levels of reciprocalmatching between subject and playback. Males with fledglingssang with particularly low versatility and approached the speakeraggressively, whereas males with nestlings overlapped more andretreated quickly. Finally, older males matched more but overlappedless.     

Male singing behaviour and female presence in the territory in whitethroats Sylvia communis

Unmated male songbirds usually change their vocal behaviour when females enter their territories. Either the males court the females by changing the rate or pattern with which their normal long-ranging full songs are emitted, or they shift to special displays and long- or short-ranging vocalisations. In this study we quantified how female presence and behaviour affect the singing behaviour of male whitethroats. In the presence of a female the male frequently performed song flights, maybe to locate the female before it was courted, with sequences of diving-song displays. The courtship was interrupted by periods of perch songs. Female dscharp calls and short movements made the males initiate or resume courtship, whereas short horizontal jumps made the males intensify their courtship. Overall, the males changed their dual-function song activity in females' presence by emitting fewer perch songs and more flight songs. The quiet diving songs were only emitted during direct courtship of a female. The song types emitted immediately before, during, and after courtship are all highly variable, thus allowing for a quick assessment of the male's song repertoire. The courtship was also interrupted by periods of male woid calling, a call that is known to have a deterring effect on rival males. Bouts of woid calls were usually followed by song flights, again probably to locate the female that might have moved out of sight, or maybe to locate potential rival intruders. The latter was supported by an increased intrusion rate during female presence. Communicated by P. McGregor     

Song types and their structural features are associated with specific contexts in the banded wren

We studied the use of song types and their acoustic features in different social contexts in the banded wren (Thryothorus pleurostictus), a resident tropical songbird in which males possess about 20 distinctive song types varying in duration, bandwidth, note composition, and trill structure. We recorded six focal males intensively for four days each while we observed context information such as during versus after dawn chorus, presence of the female, counter-versus solo-singing, location at the edge versus centre of the territory, and proximity to the nest. All males used at least some song types differentially during each of these pairs of alternative contexts. Males also preferentially used the song types they shared with a given neighbour when interacting with that bird. Songs delivered during dawn chorus were significantly longer, wider in bandwidth, often compound (double songs), and more likely to contain a rattle or buzz and an up-sweeping trill, compared to songs delivered after dawn chorus. Similar features were also more commonly observed when birds were engaged in intense male-male interactions and boundary disputes after dawn chorus, especially when countersinging at the edge of the territory. The presence of the female caused the male to deliver song types with narrower whole-song and trill bandwidth and fewer rattles and buzzes, and song-type diversity and fraction of compound songs were higher when the female was present. Thus, in addition to using type matching and variations in song-type switching and diversity to signal different levels of aggressive intention, male banded wrens also select song types based on their acoustic structure in different social contexts.     

Coordinated and dissociated effects of testosterone on singing behavior and song control nuclei in canaries (Serinus canaria)

Temperate zone songbirds that breed seasonally exhibit pronounced differences in reproductive behaviors including song inside and outside the breeding season. Springlike long daylengths are associated with increases in plasma testosterone (T) concentrations, as well as with increases in singing and in the volume of several brain nuclei known to control this behavior. The mechanisms whereby T can induce changes in behavior and brain, and whether or not these effects are differentially regulated, have recently begun to be examined, as has the question of the relative contributions of T and its androgenic and estrogenic metabolites to the regulation of this seasonal behavioral and neural plasticity. In this experiment, we examined the effects of T, 5alpha-dihydrotestosterone, or 17beta-estradiol treatment on castrated male canaries housed on short days and compared neural and behavioral effects in these males to similarly-housed males given only blank implants. We observed that only T treatment was effective in eliciting significant increases in singing behavior after 11 days of hormone exposure. In addition, T alone was effective in increasing the volume of a key song production nucleus, HVC. However, at this time, none of the steroids had any effects on the volumes of two other song control nuclei, Area X of the medial striatum and the robust nucleus of the arcopallium (RA), that are efferent targets of HVC, known to be regulated by androgen in canaries and also to play a role in the control of adult song. T can thus enhance singing well before concomitant androgen-induced changes in the song control system are complete.     

Ultrasonic singing by the blue-throated hummingbird: a comparison between production and perception

Blue-throated hummingbirds produce elaborate songs extending into the ultrasonic frequency range, up to 30 kHz. Ultrasonic song elements include harmonics and extensions of audible notes, non-harmonic components of audible syllables, and sounds produced at frequencies above 20 kHz without corresponding hearing range sound. To determine whether ultrasonic song elements function in intraspecific communication, we tested the hearing range of male and female blue-throated hummingbirds. We measured auditory thresholds for tone pips ranging from 1 kHz to 50 kHz using auditory brainstem responses. Neither male nor female blue-throated hummingbirds appear to be able to hear above 7 kHz. No auditory brainstem responses could be detected between 8 and 50 kHz at 90 dB. This high-frequency cutoff is well within the range reported for other species of birds. These results suggest that high-frequency song elements are not used in intraspecific communication. We propose that the restricted hummingbird hearing range may exemplify a phylogenetic constraint.     

Preliminary report on predatory behavior and meat sharing in tschego chimpanzees (Pan troglodytes troglodytes) in the Ndoki forest,northern Congo

Predatory behavior ofPan t. troglodytes in the Ndoki Forest was confirmed by both direct observation and fecal evidence. Eight out of 214 fecal samples (3.7%), collected during 16 months, contained vertebrate tissue. The prey species were a terrestrial bird, two monkey species including crowned guenon, a squirrel, and probably a pangolin. This rate suggested that predation in the Ndoki population can occur as frequently as in other populations. Chimpanzees were also directly observed to eat an infant crowned guenon, a hornbill, and a duiker. An adult female used a branch apparently in an attempt to drive out a hornbill from its nest hole, though no bird was observed to come out. Chimpanzees were attracted to meat, and were observed begging and sharing over the meat. Predatory behavior is common toPan andHomo, but not toGorilla, implying that the common ancestor of the former two genera acquired this behavior after separating from gorillas.     

Androgens modulate song effort and aggression in Neotropical singing mice

Androgens are an important class of steroid hormones involved in modulating the expression and evolution of male secondary sex characters. Vocalizations used in the context of aggression and mate attraction are among the most elaborate and diverse androgen-dependent animal displays as reflected in a rich tradition of studies on bird song and anuran calls. Male Alston's singing mice (Scotinomys teguina) commonly emit trilled songs that appear to function in male-male aggression. In this study, we experimentally manipulated androgens in singing mice to assess their role in modulating aggression and song effort. Testosterone- and DHT-treated animals retained aggressive and song attributes similarly. However, castrated mice administered empty implants showed more subordinate behavior and sang fewer songs that were shorter, lower in power, higher in frequency, and less stereotyped. The extensive effects of androgens on a suite of phenotypes highlight their role in linking gonadal status with decisions about investment in reproductive behaviors.