INCOMPLETE SONG STROPHES IN THE CHAFFINCH FRINGILLA COELEBS L.: GENERAL INFLUENCES ON A SPECIFIC BEHAVIOURAL OUTPUT

ABSTRACT

Incomplete song strophes in free-living territorial Chaffinch males can be induced by different experimental as well as natural stimulus situations including replay of species- specific song, approaching of human beings, and aggressive encounters with con-specific males. While the first post-stimulus song strophe is shortest the following ones gradually attain their full number of elements again. The strength of this reaction differs with regard to different stimuli.     

Song structure in the Hoopoe (Upupa epops) — Strophe length reflects male condition

Summary The structure of Hoopoe (Upupa epops) song is analysed in a colour ringed population in southern Spain. The song of males in this species is very simple, with a repertoire size of one. The strophes of a male only differ in the number of elements that they include (strophe length), and strophe length is the main song feature differing between males. During the prelaying period each individual used mainly strophes of only two lengths, between 2 and 6 elements per strophe, and mean strophe length of males during this period was highly repeatable. However, some males changed the range of strophe types produced and decreased their mean strophe length after unsuccessful breeding or spending long periods of time singing (unpaired males). These changes show that strophe length is phenotypically plastic, and suggest that singing long strophes is energetically more costly than singing short ones. The significant relationship between strophe length and body condition, and the fact that long strophes were associated with longer previous pauses than short strophes, also suggest that increasing strophe length is costly. All these findings are in accordance with the hypothesis that strophe length reflects male condition in the Hoopoe, although it is not clear what the actual cost of singing long strophes is.

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Struktur des Gesangs des Wiedehopfs (Upupa epops) — Strophenlänge reflektiert Männchen-Qualität

Zusammenfassung Die Struktur des Gesangs des Wiedehopfs wurde in einer farbberingten südspanischen Population untersucht. Der Gesang des Männchens ist sehr einfach und umfaßt nur ein Repertoire. Die Strophen eines Männchens differieren nur in der Anzahl Elemente (Strophenlänge), und die Männchen unterscheiden sich vor allem in der Strophenlänge voneinander. In der Vorbrutphase verwendeten die Männchen meist nur zwei verschieden lange Strophen, bestehend aus 2 und 6 Elementen je Strophe, und die durchschnittliche Strophenlänge war in dieser Phase sehr konstant. Nach Brutverlust oder bei kontinuierlich singenden, ledigen Männchen kam es zu einer Verkürzung der mittleren Strophenlänge. Die Strophenlänge ist phänotypisch plastisch, und lange Strophen zu singen scheint energetisch aufwendiger als kurze Strophen. Der enge Zusammenhang zwischen Strophenlänge und männlicher Konstitution einerseits und die Beobachtung, daß lange Strophen mit langen Pausen korrelieren andererseits, zeigen ebenfalls, daß längere Strophen energetisch aufwendiger sind. Die wirklichen Kosten dafür sind jedoch noch nicht bekannt.

     

Attraction of Hoopoe Upupa epops females and males by means of song playback in the field: influence of strophe length

Experimental Hoopoe Upupa epops songs prepared with synthetic sound to differ in strophe length were used to test whether Hoopoe females prefer long strophes. The songs were broadcast simultaneously in the field from two loudspeakers situated 100 m apart, in early spring, when females actively search for mates. The playbacks attracted a total of 87 individuals, both males and females, with a maximum of five individuals (three males and two females) per trial. A female was considered to have been attracted by the song broadcast from a loudspeaker when she approached unaccompanied by a male, and when there was no male nearby. A total of 15 females chose one of the songs and significantly more were attracted by the one with long strophes. These results suggest that in the Hoopoe, male song attracts females, and that strophe length is a sexually selected song cue. There were no differences in the number or kind of males (classified according to strophe length) attracted by each playback. Frequently the experiment attracted more than one male simultaneously. These aggregations cannot be explained as territorial responses, and their significance is discussed together with that of natural spontaneous groupings of displaying males. Apparently males aggregate where they expect to find females.     

Strophe Length in Spontaneous Songs Predicts Male Response to Playback in the Hoopoe Upupa epops

Hoopoe (Upupa epops, Coraciformes) males produce a very simple song during the breeding season in order to attract females and repel intruders. Strophes vary in length (i.e. number of elements) both within and between males, and previous studies have shown that this song cue is positively correlated with male condition and breeding success. In the present study we tested whether strophe length of males influences male behaviour during intra‐sexual contests, in a colour‐ringed population in southeast Spain. Paired males were presented with a recorded song with long strophes during the pre‐laying period, while they were near their mates, in order to provoke male mate‐defence behaviour. Most males responded to the playback, but the strategy of defence adopted depended on their own strophe length in spontaneous songs recorded before the experiments. While singing responses were common to most of the males, only those using long strophes adopted the most risky strategy of approaching the loudspeaker. However, the males that approached produced abnormal songs during playback, that were shorter and with fewer strophes than those of males that did not approach, and used shorter strophes in comparison with spontaneous songs before the experiment. These differences in quality of the song produced in response to the playback suggest that long‐strophe males were basing their response mainly on attacking rather than singing, while short‐strophe males tried to resolve the contest at a distance by means of their song. These results show that strophe length reflects some component of the competitive ability of males (either physical strength or aggressiveness) in the hoopoe, which together with previous results regarding its role for female choice, show that it is a sexual signal with dual 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     

Versatility and Stereotypy of Free-Tailed Bat Songs

In mammals, complex songs are uncommon and few studies have examined song composition or the order of elements in songs, particularly with respect to regional and individual variation. In this study we examine how syllables and phrases are ordered and combined, ie “syntax”, of the song of Tadarida brasiliensis, the Brazilian free-tailed bat. Specifically, we test whether phrase and song composition differ among individuals and between two regions, we determine variability across renditions within individuals, and test whether phrases are randomly ordered and combined. We report three major findings. First, song phrases were highly stereotyped across two regions, so much so that some songs from the two colonies were almost indistinguishable. All males produced songs with the same four types of syllables and the same three types of phrases. Second, we found that although song construction was similar across regions, the number of syllables within phrases, and the number and order of phrases in songs varied greatly within and among individuals. Last, we determined that phrase order, although diverse, deviated from random models. We found broad scale phrase-order rules and certain higher order combinations that were highly preferred. We conclude that free-tailed bat songs are composed of highly stereotyped phrases hierarchically organized by a common set of syntactical rules. However, within global species-specific patterns, songs male free-tailed bats dynamically vary syllable number, phrase order, and phrase repetitions across song renditions.     

ANNUAL CHANGES OF LEARNED BEHAVIOUR—VARIATION OF SONG PATTERN IN FREE-LIVING CHAFFINCHES,FRINGILLA COELEBS,DURING THE BREEDING SEASON

ABSTRACT

Seasonal changes of parameters of full song were studied in a free-living population of chaffinches Fringilla coelebs during one entire reproductive period. Approximately 7000 strophes sung by 14 male chaffinches were recorded and analysed by sonography and a particular oscillographic method. While the general pattern of song strophes, i.e. characteristics of elements, number and arrangement of phrases, and final flourish, remained constant throughout the reproductive period, full song varied with respect to the repetition rate of strophes, number of strophe types used, intensity of singing, duration of strophes, and percentage of incomplete strophes sung. These changes are discussed as results of learning processes, social interactions in the population, and endogenous mechanisms activating memorized information.     

The Role of Song Phonology and Syntax in Vocal Learning Preferences in the Song Sparrow,Melospiza melodia

Are young songbirds ready to learn virtually any song, or are they predisposed to learn songs of their own species? To explore this question tests were conducted on the equipotentiality of auditory song learning stimuli in the song sparrow. 23 males reared as nestlings were exposed to tape recordings of their own and other species songs in early life and subsequent song production was analyzed for imitations. Birds exposed to natural song sparrow songs, including their fathers', and equal numbers of swamp sparrow songs, strongly preferred conspecific songs. They neither favored nor eschewed paternal songs despite having had access to them for 6–10 days as nestlings. In three other experiments synthetic songs were used in which some properties were held constant and others were systematically varied. Birds were exposed to 1–4 segmented songs varying in phrase order, tempo and syllable number, each synthesized in two versions, one from conspecific and the other from heterospecific (swamp sparrow) song syllables. With one-segmented songs (alien syntax) subjects favored conspecific over heterospecific syllable songs. Heterospecific syllables were rendered more acceptable by incorporation into two-segmented trilled songs (more song sparrow-like syntax). Heterogeneous summation of phonological and syntactical cues appeared to occur. There was also evidence of interaction between phonology and syntax. When another phrase type, the note complex, was added, in three- and four-segmented songs, a preference for conspecific syllables reappeared. Heterospecific syllables may be more readily accepted as a trilled sequence than without repetition, as in a note-complex. When phrase structure within four-segmented songs was varied, birds favored patterns most like normal conspecific song. We conclude that there are innate learning preferences in the song sparrow, based on note and syllabic structure (phonology and syllabic syntax), and temporal organization of phrases (segmental syntax), differing from those of the closely related swamp sparrow, Melospiza georgiana, in which song syntax plays no role in learning preferences.     

Song Learning in the Anna Hummingbird (Calypte anna)

Songs of wild male Anna hummingbirds (Calypte anna) consist of syllables grouped into phrases. Nearest neighbors tend to share similar syllable types, rhythms and syntax. Songs from different localities contain different syllable types, syntax and repetition indices. A male raised by hand in isolation produced a song consisting of highly variable syllable types of a wide frequency range. The song was simple in structure, and syllables were not grouped into phrases. Three males raised by hand as a group sang songs containing two stereotyped syllable types sung in alternating sequence and without phrase structure. These three males shared syllable types and syntax. The data from our study indicate that despite its relatively simple syrinx the Anna hummingbird learns syllable types, frequency, rhythm and syntax (as do oscines with their more complex syringes) during the song development process.     

Species Recognition by Song in the Veery (Catharus fuscescens: Aves)

Territorial male veeries (Catharus fuscescens) were presented with three series of reorganised songs to determine the functional properties of song structure. Songs consist of three parts: a low frequency initial phrase, a higher frequency middle phrase, and again a lower frequency end phrase. The latter two consist of vibrato syllables. Three series of experiments were performed, using various combinations of song syllables. In Series I, songs consisted of repetitions of a single syllable, one from each part of the song. Veeries responded to syllables from the middle and end phrases as to normal songs, both in localisation and in vocal responses. However, they showed little localisation and vocalisation responses to the introductory syllables. In Series II and III, veeries responded significantly more to songs in which syllables from the middle and end phrases were presented in proper sequence, rather than not. The minimum requirements for intraspecific recognition were determined in relation to the number and order of syllables in the song.     

Song complexity and song structure in the Moustached Warbler Acrocephalus melanopogon

We examined different song parameters leading to a complex song configuration, and song output (production), and their relation in male Moustached Warblers and discuss them with reference to female choice. With more than 120 different syllables per two minutes of song, male Moustached Warblers can be regarded as one of the most complex singers within the genus Acrocephalus . We found significant differences between males for almost all song parameters investigated (repertoire size, switching and repetition rate, song speed and strophe length) but not for time spent singing per 20 minutes. This individual variation probably is an important cue for female mate choice. Male Moustached Warblers achieve song complexity mainly via frequent syllable switching. Song complexity seems to be consistent throughout the song and our results suggest that females could assess the overall song complexity of a singer by examining even very short song bouts. Furthermore, a high proportion of motifs – clusters of syllables with the same sequence – occurs within the song of each male which would also facilitate assessment of song complexity by females. However, repertoire size and strophe length were positively related, thus it remains to be investigated which song feature, if any, females actually use.     

Song Learning in Bengalese Finches: a Comparison with Zebra Finches

Male Bengalese finches, Lonchura striata var. domestica, learn their song from an adult male conspecific with whom they can interact at 35 to 70 days of age and normally-raised males fail to reproduce song which they have only heard before or after this time. Birds which have been raised by their mother alone and those which have been deprived of a song tutor during the learning phase produce abnormal songs with indistinct elements and little or no phrase structure; this is typical of males which fail to hear adult song during their development. These songs are unstable and are replaced by normal songs, if there is an opportunity to learn from an adult male conspecific. Presumably, this flexibility in the time when young males learn acts as a safeguard to ensure that normal conspecific song is produced. These results bear striking similarity to those on zebra finch song development. Differences between the two species, especially in the learning of call notes by female zebra finches, are discussed.     

青海门源赭红尾鸲鸣唱方言的时间稳定性

鸟类的鸣唱方言是研究非人类文化进化及其与种群遗传分化相互作用的理想素材。该研究通过比较跨度8年的2001年和2009年青海门源赭红尾鸲(Phoenicurus ochruros rufiventris)鸣唱,研究结果显示,青海门源赭红尾鸲的种特异性音节、经典唱段中的部分音节、典型唱段结构和鸣唱方言的基本形式都具有较高的时间稳定性。2009年赭红尾鸲唱段曲目多于2001年,共享唱段出现了一定的分化,唱段的共享程度和鸣唱的相似性与个体领域间的距离相关,相邻个体的鸣唱相似性程度高于较远距离的个体。     

Sexually dimorphic phrase organization in the song of the indris (Indri indri)

Animal acoustic communication often takes the form of complex sequences, composed of multiple distinct acoustic units, which can vary in their degree of stereotypy. Studies of sequence variation may contribute to our understanding of the structural flexibility of primates' songs, which can provide essential ecological and behavioral information about variability at the individual, population, and specific level and provide insights into the mechanisms and drivers responsible for the evolutionary change of communicative traits. Several methods have been used for investigating different levels of structural information and sequence similarity in acoustic displays. We studied intra and interindividual variation in the song structuring of a singing primate, the indri (Indri indri), which inhabits the montane rain forests of Madagascar. Indri groups emit duets and choruses in which they combine long notes, short single units, and phrases consisting of a variable number of units (from two to six) with slightly descending frequency. Males' and females' contributions to the song differ in the temporal and frequency structure of song units and repertoire size. We calculated the similarity of phrase organization across different individual contributions using the Levenshtein distance, a logic distance that expressed the minimum cost to convert a sequence into another and can measure differences between two sequences of data. We then analyzed the degree of similarity within and between individuals and found that: (a) the phrase structure of songs varied between reproductive males and females: female structuring of the song showed a higher number of phrases if compared to males; (b) male contributions to the song were overall more similar to those of other males than were female contributions to the song of other females; (c) male contributions were more stereotyped than female contributions, which showed greater individual flexibility. The picture emerging from phrase combinatorics in the indris is in agreement with previous findings of rhythmic features and song repertoire size of the indris, which also suggested that female songs are potentially less stereotyped than those of males.     

Territorial reactions of male Yellowhammers (Emberiza citrinella) toward a specific song structure

Male songbirds assess their rivals by listening to their songs and, in some species, are especially sensitive to certain parts of the song. Yellowhammers (Emberiza citrinella) sing songs with different structures consisting of an initial phrase of stereotyped and repeated notes in a trill, and a terminal phrase, present or not, which consists of low or high frequency whistles that we called elements. We analyzed 1,055 songs from 25 different males and found that four different structures could be distinguished in a French Yellowhammer population. We found that the frequency ranges of the elements were more constant across individuals than the ranges of the notes, and among them, the low frequency element was nearly twice as conserved as the high frequency element. Then, in the wild, we tested the territorial responses of males to the four different structures and found that the full song structure, which is composed of the initial phrase followed by a high frequency element and a low frequency element, induced stronger territory defence responses from the males than any of the other structures. As only the structure containing the initial phrase and the low frequency element also induced a strong response, we propose that the main element responsible for the enhanced reaction of the males is the low frequency element, which is consistent with the fact that it is more conserved than the other constituents.     

Frequency shift in homologue syllables of the Ortolan Bunting Emberiza hortulana

Results of this study indicate that in the Ortolan Bunting Emberiza hortulana, syllables of the same shape on sonograms (i.e. homologue syllables) often significantly differ between males in frequency parameters. Typically, homologue syllables of different males in the studied population had a similar bandwidth but shifted minimal and maximal frequencies. We found no strong evidence supporting that the frequency of homologue syllables is affected by the body size variation of males. Besides, frequency parameters of different song types within a male's repertoire did not correlate with each other. Moreover, we found that some males within the population sing two versions of apparently 'the same' song type, which differ in frequency parameters of syllables. Such different frequency versions were sung with eventual variety, which suggests that they are treated as different song types by birds. All these results support the idea that the fine acoustic structure of syllables (and song) is under a strong influence of the acoustic template (i.e. depend mainly on from whom the song was copied). We also found that the frequency of initial syllables within the song strophe is much more variable between males than in case of final syllables. Regardless of the great between-individual variation in initial syllable frequency, the syllables forming the final part of the song are kept within a very restricted bandwidth. These results support our earlier finding that strict syntactic rules of song formation exist in this species. These rules condition the acoustic variation of the initial and final part of the song. At least potentially, such a system enables species recognition and individual variation irrespective of repertoire level. Results of this study indicate that more attention should be paid to the problem of minimal units of song repertoire and to identity of such units within the bird population.     

Extrapair paternity in the Hoopoe Upupa epops: an exploration of the influence of interactions between breeding pairs, non-pair males and strophe length

Previous studies of the Hoopoe Upupa epops have shown that the strophe length of male songs influences female mate choice, and is correlated with female reproductive rates and male production of fledglings in the male’s own brood. However, frequent interactions between breeding pairs and non‐pair males suggests that extrapair copulations could occur and could affect the real number of fledglings sired by males, and therefore the relationship between strophe length and breeding success. Here we analyse the incidence of interactions between breeding pairs and non‐pair males, and of extrapair paternity, the interrelation of these parameters, the influence of male strophe length on them, and whether extrapair fertilizations affect the correlation between strophe length and breeding success of males, in a colour‐ringed population of Hoopoes in south‐eastern Spain. Multilocus DNA‐fingerprinting revealed that 10% of the broods contained offspring sired by extrapair males, representing 7.7% of the chicks. However, the interactions between pairs and non‐pair males were more frequent, with more than 25% of broods being visited by non‐pair males, and about 10% being helped (fed or defended) by males other than the nest owner. Most of these relationships were apparently attempts by visitor males to obtain copulations with paired females, or to obtain access to such females or nests in future breeding attempts. However, there was no significant link between the detection of interactions with alien males in a nest and the occurrence of extrapair paternity in it, indeed extrapair paternity was found in only 30% of the nests with interactions, and therefore the detection of visits or helping by non‐pair males cannot be considered evidence of extrapair paternity in visited or helped broods. Males that sang with long strophes never suffered losses of paternity within their broods, while 25% of males that sang with short strophes did. However, these differences were not significant. Nevertheless, strophe length of males was significantly positively correlated with per brood and seasonal production of fledglings after accounting for losses of paternity within their own broods.     

THE SINGER AND THE SONG: ON THE RECEIVING END OF BIRD SONG

Variation in singing behaviour between males can involve fixed differences such as the song type composition of repertoires, as well as more flexible effects such as matched counter-singing (Krebs & Kroodsma, 1980; Section III. 4), differences in bout length (the number of songs in a period of song) and changes in strophe length. Short-term strophe length changes seem to be related to the willingness and ability of males to respond strongly to playback. Whether this is because strophe length indicates motivation or the degree of exhaustion of the neuromuscular song-production system, or both, is currently unclear.