Patterns of dawn singing by Buff-breasted Flycatchers

ABSTRACT.   Many passerine species exhibit a "dawn chorus"—a bout of intense singing activity before or at dawn, but our understanding of this phenomenon is poor. Tyrant flycatchers (Tyrannidae) exhibit pronounced daily bouts of dawn singing. I documented this behavior in several populations of Buff-breasted Flycatchers ( Empidonax fulvifrons ) in Arizona, tape recording >30,000 songs of 23 individuals during dawn singing. Individual males sang a dawn bout each morning, even during breeding phases when daytime song was almost completely absent. Dawn bouts began 5–10 min before local civil twilight and continued for 25–30 min. Each male possessed two song types delivered at high rates during dawn singing (four times the rate during sustained daytime singing). Song rate varied significantly over the course of dawn bouts, increasing to 55 songs / min at mid-bout, then declining to the end of the bout. Type 2 songs comprised about 30% of songs during dawn singing, and decreased significantly in proportion during the final 10 min of the bout. Songs of the two types were delivered in a nonrandom fashion. Males sang at locations near territory boundaries and pairs of neighbors engaged in counter-singing from the same locations each morning. A number of dawn singing bouts ended with attempted or successful copulations. These observations are consistent with the social dynamics hypothesis for the functional significance of dawn singing in this species.     

Conveying information with one song type: changes in dawn song performance correspond to different female breeding stages

Many bird species participate in dawn singing, a behaviour categorized by intensive singing at dawn; however, many of these species deliver only one song type at dawn. While there are many proximate and ultimate hypotheses for why birds sing at dawn, little is known about whether males are able to vary one simple song to convey different information. We used autonomous acoustic recorders to record dawn songs of field sparrows and quantified three parameters of singing performance: 1) bout length, 2) song rate, and 3) song complexity. We found that males sang the longest dawn bouts during their mate's fertile period, the highest song rates during the post-fertile period, and the most complex songs during the pre-fertile period. The change in dawn singing behaviour with their mate's breeding stage suggest the purpose of dawn song may be context dependent. Our results demonstrate that male field sparrows, while only having a single song type sung at dawn, may convey information for both intra- and intersexual purposes. While it is generally assumed that dawn song has a specific function, the variability in the duration, rate, and complexity of dawn song in field sparrows suggests that they are conveying different information and that dawn song likely has multiple functions.     

Singing by male and female Kloss gibbons (Hylobates klossii) in the Peleonan Forest, Siberut Island, Indonesia

Kloss gibbons (Hylobates klossii) are endemic to the Mentawai Islands in Indonesia and are one of only two gibbon species in which mated pairs do not sing duets. This is the first long-term study of the factors influencing the singing activity of Kloss gibbons within a northern Siberut Island population and follows two previous studies in central Siberut nearly 30 years ago. We collected data on the presence/absence of male and female singing within the study area on 198 days and within a focal group on 47 days. Rainfall during the time period in which they normally sing inhibits singing in both males and females. Our study supports the hypothesis that male and female songs function in intrasexual resource defence, as singing is associated with singing by same-sex neighbours, and same-sex choruses are more likely to occur after one or more days of silence (from that sex), suggesting there is pressure for individuals to communicate with same-sex neighbours regularly. Singing was not coordinated within a mated pair, suggesting that vocal coordination of the pair has been lost with the loss of the duet and that Kloss gibbon songs do not convey information to neighbours about the strength of the pair bond. On days when males sang predawn, females were more likely to sing after dawn and earlier in the morning. Additionally, the number of groups singing in female choruses was positively associated with the number of males that had sung in the predawn male chorus. We suggest that female songs have an intersexual territory defence as well as an intrasexual function.     

Dawn song of male blue tits as a predictor of competitiveness in midmorning singing interactions

During the dawn chorus, territorial male songbirds vocalise intensively within signalling range of several conspecific males and can therefore be considered members of a busy communication network. The more or less continuous singing over a long period of time under standardised stimulus conditions makes the dawn song a potentially important information source both for simple receivers and for eavesdroppers. Male blue tits (Parus caeruleus) vary in features of their dawn song, e.g. older males sing longer strophes, and females choose males that sing longer strophes as extra-pair partners. However, so far, dawn song in the blue tit has been investigated separately from other singing behaviour of the same males. In this study, we investigate aspects of blue tit male quality, reflected in dawn song characteristics, and their predictive value for how males behave during singing interactions later in the morning. We acted as simple receivers by recording the singing activity of one male at a time at dawn and compared features of its dawn song, such as onset before sunrise, repertoire size, mean bout length, strophe length and percentage performance time to responses of the same male to a territory intrusion simulated by playback of synthesised songs later during the same morning. We assume that an aggressive response towards an intruder will involve a fast approach to the loudspeaker broadcasting strophes of blue tit song, searching for the intruder (flying around), and a high amount of counter singing and overlapping of the intruders songs. Aspects of vigour of response to the simulated intrusion could be predicted from all five investigated dawn song parameters as well as male age. This is, to our knowledge, the first indication that a simple receiver could extract reliable information from a males dawn singing behaviour about its competitiveness later in the day.Communicated by P.K. McGregor     

Calling in wild silvery gibbons (Hylobates moloch) in Java (Indonesia): behavior, phylogeny, and conservation

Hardly any behavioral data are available for the silvery gibbon (Hylobates moloch), an endangered primate that is endemic to the island of Java, Indonesia. We studied the singing behavior of the easternmost population of this species in the Dieng mountains, central Java, in 1998-1999. We aimed to document the timing of singing, quantify the amount of singing by the respective sexes, and explore the role of bioacoustics in density estimation. A total of 122 song bouts in at least 12 groups were monitored. No duet songs were heard. Most of the song bouts (91.5%) were female solo song bouts or female scream bouts. In contrast to an earlier study on the westernmost population of silvery gibbons, during which few if any male songs were heard, at least 8.5% of the song bouts in our study were male solo song bouts. They were significantly longer in duration than the female songs. All male song bouts uttered before dawn (0520 hr) were produced in a chorus fashion, with at least three individuals participating. Choruses occurred about once every 8.5 days, and lasted longer and occurred earlier than female solo song bouts. Most male songs (60%) started between 0355-0440 hr, when it was still dark. All female songs, in contrast, started after 0500 hr, and female singing activity peaked around 0600. Regular male singing, male chorusing, and regular predawn singing have not previously been reported for silvery gibbons. Similarly separated periods of male and female solo songs and the absence of duetting have been observed in Kloss's gibbons (H. klossii) on the Mentawai Islands, and may represent synapomorphies shared by both species. The pronounced individual-specific song characteristics of silvery gibbons allow accurate mapping of groups. The density of gibbons at our study site was established to be 1.9-3.7 groups/km2, corresponding to 6.7-13.1 individuals/km2. We reassess the suitability of gibbon songs as a means of estimating the density and size of gibbon populations, and discuss the proximate causes for the absence of duetting in silvery gibbons.     

Detecting diel patterns in the songs of Chipping Sparrows using citizen-science data

Previous studies have revealed diel patterns in the songs of Chipping Sparrows (Spizella passerina), with songs shorter in duration before dawn than after. However, the extent to which this phenomenon generalizes to the full geographic range of these sparrows is unclear, as is the question of whether citizen-science data can be used to detect diel patterns in song. We analyzed all available songs of Chipping Sparrows from the Macaulay Library and xeno-canto databases and compared the distributions of song features of recordings made at different times of day. We show that, across their entire geographic range in North and Central America, Chipping Sparrows sing shorter songs before sunrise (dawn song) than after sunrise (day song). Furthermore, we show that Chipping Sparrows shorten their songs by singing fewer syllables, not by singing faster: the number of syllables per song accounts for the observed difference in duration, not the syllable nor the intersyllable duration. Our results demonstrate that recordings from public repositories can be used to determine whether daily song patterns exist in species even in the absence of prior fieldwork, and we further propose that citizen-science recordings can be used to inform cross-species hypotheses and facilitate future studies to determine whether diel patterns in song are associated with differences in social behavior.     

Corn bunting (<Emphasis Type="Italic">Miliaria calandra</Emphasis>) males respond differently to alternating and overlapping playback of song

Interactive playback experiments were used to study the signal value to the corn bunting, Miliaria calandra, of alternating and overlapping singing. We subjected 15 males to two stimuli that differed in the temporal pattern of song playback (alternating or overlapping). We measured eight characteristics of the males’ response in two categories—song output and movements. Overlapping and alternating playback elicited a similar song response, characteristic of highly aroused males. Song response correlated positively with males’ singing activity before playback, irrespective of stimulus. There were significant differences between latency of approach to the loudspeaker and number of flights. Birds approached the loudspeaker more quickly and spent more time close to it when playback alternated with their songs. The results suggest overlapping song could be interpreted as a stronger threat but elicits a more cautious, rather than stronger, response than the alternating pattern. Males were found to shorten songs during the playback compared with songs sung before and after stimulation. The only predictor of degree of song shortening was song activity before the playback began. It should, therefore, be regarded as a signal which is related to escalated, close-distance counter-singing.     

Signalling through acoustic windows: nightingales avoid interspecific competition by short-term adjustment of song timing

The function of bird song is closely linked to sexual selection through female choice and male–male competition, and thus variation in communication success is likely to have major fitness consequences for a singing male. A crucial constraint on signal transmission is imposed by background noise, which may include songs from other species. I investigated whether singing nightingales (Luscinia megarhynchos) avoid temporal overlap with the songs of other bird species in a playback experiment. I analysed the temporal song patterns of six males, each of which were exposed to songs of other species. The nightingales significantly avoided overlapping their songs with the playback songs, and started singing preferentially during the silent intervals between the heterospecific songs. This timing of song onset produced a greater variability in pause duration compared to the nightingales’ undisturbed solo singing. These findings suggest that birds adjust their song timing to avoid acoustic interference on short temporal scales, and thus are able to improve the efficiency of acoustic communication in complex sonic environments. Moreover, the results indicate that temporal song patterns can be affected by the songs of other species, and thus such influences should be taken into account when studying bird song in the field.     

Complementary neural systems for the experience‐dependent integration of mate‐choice cues in European starlings

Choice of a particular mate phenotype may arise out of experience with the very phenotypes under consideration. Female European starlings (Sturnus vulgaris) prefer males that sing predominantly long‐bout songs over males that sing predominantly short‐bout songs, and thus, song‐bout length is a phenotypic parameter instrumental in releasing the female's mate choice. The preferred long‐bout songs induce higher expression of the immediate early gene (IEG) ZENK in the female auditory telencephalon than short‐bout songs do, but this sensitivity to song length depends on the female's recent song experience. Here, we compared the experience‐dependent modulation of ZENK with that of another IEG, FOS, and report that ZENK and FOS expression in the caudomedial mesopallium and caudomedial nidopallium show different modulation properties that complement natural variation in song‐bout length. As reported previously, ZENK expression was greater in response to novel long‐bout than to novel short‐bout songs following a 1‐week experience with long‐bout but not short‐bout songs. In contrast, FOS expression was greater in response to novel long‐bout than to novel short‐bout songs following a 1‐week experience with short‐bout but not long‐bout songs. Thus, the ZENK and FOS signaling pathways are made sensitive to variation in song length by experiences with songs at opposite ends of the starling song‐variation continuum, suggesting the presence of complementary neural systems made sensitive in register with the natural axis of phenotypic variation fundamental to the female's mate choice. © 2004 Wiley Periodicals, Inc. J Neurobiol, 2005     

Long-term influence of simulated territorial intrusions on dawn and dusk singing in the Winter Wren: spring versus autumn

Males of many songbird species have peaks of singing activity at dawn and dusk. Singing during those twilight periods can function in territory proclamation, and males are suggested to adjust song output to the level of intruder pressure. We used song playback during the breeding season to simulate intrusions into territories of male Winter Wrens (Troglodytes troglodytes) shortly after dawn. We then compared male singing behaviour during the dawn and dusk chorus before and 1 day after the simulated intrusion. One day after the playback, male Wrens increased their song output before sunrise, which confirms our results from a previous study on dawn singing in autumn territories. At dusk, on the evening following the playback, males slightly increased song output after sunset, but singing activity at dusk was generally very low. We found no significant changes of song output after sunrise, before sunset, and between 2 days of control without playback. These results are consistent with the hypothesis that dawn and dusk singing is important for territory defence in spring. Unlike in autumn, however, increased singing in spring at dawn and dusk could also serve to defend other resources such as fertile mates or to strengthen the pair bond after a territorial challenge. In comparison with the results on autumnal singing, male Wrens started singing earlier at dawn during the breeding season, and they generally sang more songs at dawn and immediately after playback. The increase in absolute numbers of songs sung in the morning after playback seemed greater in spring than in autumn; however, the proportional increase relative to overall song output was similar in both seasons.     

An Interactive Playback Experiment Shows Song Bout Size Discrimination in the Suboscine Vermilion Flycatcher (Pyrocephalus rubinus)

Many aspects of the social behaviour of birds are mediated by vocal displays, and variation in song output or song structure conveys different information to receivers. After nest construction begins, when vermilion flycatcher (Pyrocephalus rubinus) females are potentially fertile, males increase their song rate during the dawn chorus. A previous study failed to give evidence that males discriminate among song rates. However, males sing in sequences of songs (song bouts), and an increase in song rate may be achieved by increasing the number of bouts, the number of songs in each bout (bout size) or both. Studying a vermilion flycatcher population in Mexico City, we evaluated whether dawn song rate is related to song bout size or to number of bouts. Bout size correlated with song rate and differed among males. We hypothesized that longer bouts are more threatening signals than shorter ones and predicted a stronger response by males towards the former. We exposed each male to three playback treatments: (1) Long song bout (Long), in which we replied to the male with twice the number of songs he sang in the bout, (2) Short song bout (Short), in which we played half the number of songs sung by the male and (3) Control, this was the same as the Long treatment but we used songs from a related species, the tropical kingbird (Tyrannus melancholicus). Males responded with a higher proportion of calls near the speaker when exposed to the Long treatment than during the Short or Control treatments, indicating that they discriminate among song bouts differing in size, that they may perceive longer bouts as more threatening and that they use calls rather than songs to address threatening situations. Our results suggest that song bout size is a relevant song attribute that conveys information during intrasexual interactions.     

白眉长臂猿鸣叫的时间特征

滇西白眉长臂猿(Hylobateshoolock)鸣叫主要发生在上午,最早开始于黎明时分,最晚则在下午16:30以后。平均开始时间为09:05,SD=1095min(N=70,范围07:12～16:30),持续时间为197min,SD=934min(N=55,R=4～50)。多数鸣叫发生在07:00～10:00之间(80%)。不同季节鸣叫发生时间有显著差异,可能与黎明时间(光亮度)不同有关,但持续时间无差异。同一季节异地间鸣叫持续时间差异显著。气候、猿群密度、栖息地状态对鸣叫有一定影响,但未见明显相关性。与黑长臂猿的种间比较表明,白眉长臂猿的鸣叫声在时间分布上有较大的散开度,持续时间也较长,二者有显著差异。     

Interspecific song imitation by a Prairie Warbler

Song development in oscine songbirds relies on imitation of adult singers and thus leaves developing birds vulnerable to potentially costly errors caused by imitation of inappropriate models, such as the songs of other species. In May and June 2012, we recorded the songs of a bird that made such an error: a male Prairie Warbler (Setophaga discolor) in western Massachusetts that sang songs seemingly acquired by imitating the songs of a Field Sparrow (Spizella pusilla). Another song type in the bird's repertoire was a near‐normal Group A Prairie Warbler song, but the bird used this song in contexts normally reserved for Group B songs. Despite its abnormal singing behavior, the aberrant bird successfully defended a territory and attracted a mate that laid two clutches of eggs. Results of playbacks of the focal bird's heterospecific song suggested that neighboring conspecific males learned to associate the Field Sparrow‐like song with the focal male, and responded to the song as if it were a Prairie Warbler song. Our evidence suggests that the focal bird's aberrant singing evoked normal responses from potential mates and rivals. If such responses are widespread among songbirds, the general failure of heterospecific songs, once acquired, to spread through populations by cultural transmission is probably not attributable to a lack of recognition by conspecifics of the songs of heterospecific singers.     

Differential effects of moving versus stationary territorial intruders on territory defence in a songbird

1.  In territorial contests, not only acoustic or other signals, but also the movements of a territorial intruder are likely to influence the response of a resident.
2.  We tested this movement hypothesis by simulating moving vs. stationary intruders into the territories of winter wrens Troglodytes troglodytes , using the same non-interactive song playbacks in both treatments.
3.  Male winter wrens showed a different long-term singing reaction in response to a moving than to a stationary intruder.
4.  One day after experiencing an intruder that was switching between three locations, residents started to sing earlier before sunrise, and they sang more and longer songs at dawn than before the intrusion.
5.  Residents receiving the same playback from one location only reacted by starting to sing later relative to sunrise, and by singing fewer and shorter songs than before the intrusion.
6.  We could not discriminate between the treatments when examining the short-term singing reactions during and immediately after the playbacks. However, our results clearly demonstrate an effect of the spatial behaviour of territorial intruders on the long-term territory defence of residents at dawn, about 24 h after an intrusion.
7.  We argue that spatial behaviour of territorial intruders should be an integral part of the study of animal territory defence behaviour. Investigating long-term changes in territory defence at dawn is a sensitive tool for discriminating between different types of intruders.     

The song structure and seasonal patterns of vocal behavior of male and female bellbirds (Anthornis melanura)

The bellbird (Anthornis melanura) is a honeyeater endemic to New Zealand, which uses song to defend breeding territories and/or food resources year round. Both sexes sing and the song structure and singing behavior have not yet been quantified. The number of song types, spectral structure, repertoire size, and singing behavior of male and female bellbirds was investigated for a large island population. Song types differed between the sexes with males singing a number of structurally distinct song types and females producing song types that overlapped in structure. Singing behavior also differed between the sexes; males often sung long series of songs while females sung each song at relatively long and variable intervals. Singing by both sexes occurred year round but the frequency of male and female singing bouts showed contrasting seasonal patterns. The frequency of female singing bouts increased as the breeding season progressed, whereas male singing bouts decreased. In contrast to almost all studied passerines, female bellbirds exhibited significant singing behavior and sung songs of complex structure and variety that parallel male song. These results provide a quantitative foundation for further research of song in bellbirds and in particular the function of female vocal behavior.     

Sound Spectrum Characteristics of Songs of Hainan Gibbon (Nomascus hainanus)

Gibbons are characterized by their species-specific calls, or songs. There are few studies of songs of Hainan gibbon (Nomascus hainanus). To study the sound spectrum characteristics and test for intergroup differences in Hainan gibbon song, we studied the singing behavior of Hainan gibbons in Bawangling National Nature Reserve, Hainan Province, China, intermittently from August 2002 to February 2013, collecting 184 recordings. Our results show that: 1) Hainan gibbon song bouts occur mainly 0–4 h after dawn. 2) The songs of adult males living in groups are composed mainly of one to three short notes and one to five long notes, while solitary adult male songs consist only of long frequency modulated notes and no short or single notes. 3) The song chorus is dominated by adult males, while females add a great call. Males do not have a great call, unlike those in other gibbon species. There are no female solos. 4) The sound spectrum frequency is similar in adult males living in two different groups, but the duration of the first long note differed significantly between the groups. The sonic frequencies of male and female songs are lower than those of other gibbons: no more than 2 kHz. Hainan gibbon sound structure is simple, although females participate in the chorus, reflecting their primitive status among gibbon species.     

Responsiveness of a male Mueller's gibbon to his own species-song,that of a lar gibbon,and a synthetic song of similar frequency

The study compared the responsiveness of a captive male Mueller's gibbon to audio recordings of dawn songs of wild-living male Mueller's gibbons and lar gibbons, and to a synthetic song constructed from screech owl vocalizations. Though wild-caught, the subject had not been exposed to songs of his own species for at least 10 years, and in fact, only rarely performed the dawn song himself. Initially, the subject responded vigorously to all three recordings, with no preference being shown for the recording of his own species. However, a very strong preference for Mueller's vocalizations did develop following a period of concentrated and exclusive exposure to Mueller's songs.     

Song Perception in the Song Sparrow: Importance of Different Parts of the Song in Song Type Classification

Song sparrow (Melospiza melodia) males have repertoires of 6 to 12 song types, each song consisting of four or five contrasting phrases. Song types vary both within individuals (a singer varies successive renditions of a type within a singing bout) and between individuals (neighbors sing slightly different versions of a type), and in both cases this variation is concentrated in the later parts of the song. We speculated that type variation in the later parts of the song might be correlated with a perceptual tendency to classify song types primarily on the basis of the earlier parts of the song. We tested this hypothesis using a laboratory conditioning technique, supplemented by a field playback experiment. In the lab, song sparrows and white crowned sparrows were trained to discriminate between two distinct song types. In test sessions, they were presented with hybrid songs synthesized from varying proportions of the two training song types. For most birds and most song pairs, song classification was influenced by all parts of the song, with the beginning elements being most important. The field playback experiment used song type matching as the response measure. Each subject was presented a hybrid stimulus song consisting of the first half of one of his song types and the second half of another of his song types. Subjects replied with both ‘front matches’ and ‘back matches’ (60% were front matches).     

Song type switching in the chaffinch, Fringilla coelebs : timing or counting?

The song of many bird species is relatively constant in form, yet each bird has more than one song type, making it an excellent model for studies of the mechanisms underlying switching between behaviour patterns. The chaffinch is a good example. Males sing with eventual variety, repeating each song type in the repertoire a few times before switching to another type. The mechanism triggering these switches is not known. We investigated long continuous recordings of spontaneous singing by six wild males to test two hypotheses: (1) that a maximum number of repetitions limits bout length; or (2) that a switch occurs after a song type bout reaches a maximum duration ('time window'). Strong evidence was found for a temporal limitation: song type bouts with many repetitions were delivered only at a fast rate, whereas bouts consisting of few songs were delivered either fast or slow. Copyright 1999 The Association for the Study of Animal Behaviour.     

Seasonal changes in the nocturnal singing routines of Common Nightingales Luscinia megarhynchos

Male Common Nightingales Luscinia megarhynchos famously sing at night. There are two distinct types of nocturnal singing routine (the dusk-to-dawn pattern of variation in song rate): (1) dusk and dawn choruses, with little or no song during the middle of the night; (2) a rapid increase in song rate after dusk, reaching a broad peak in the middle of the night, declining towards dawn, and followed by a dawn chorus. Males sing different nocturnal singing routines at different times in the breeding season. Earlier in the breeding season, most males sing Type 2 routines. Later in the breeding season, most males sing Type 1 routines, as do birds on the wintering grounds. At least some individuals may also sing Type 1 routines during the first few days after their arrival on their breeding territories, before the arrival of females. The main function of nocturnal song appears to be mate attraction. The patterns of variation in song rate over the course of the night are qualitatively similar to those predicted by stochastic dynamic programming (SDP) models of daily singing and foraging routines, for birds that do not forage at night, in circumstances when birds can pair at night (Type 2 routines), and when they cannot (Type 1 routines). The observed seasonal changes in the types of routine sung are also consistent with the predictions of these models.