Song Diversity Research Articles

Effects of Population Size on Singing Behavior of a Rare Duetting Songbird

Although the genetic and ecological effects of population declines in endangered species have been well studied, little is known of the social consequences. Changes in signaling behavior may result in disrupted communication and affect both reproductive and conflict-resolution activities. The North Island Kōkako (Callaeas wilsoni) is an endangered, duetting (i.e., alternating, coordinated singing by mated pairs) songbird endemic to New Zealand temperate rain forests. Scattered populations (approximately 1500 individuals in 13 surviving and 11 translocated populations) in isolated conservation areas of different sizes have been rescued from extirpation and are currently recovering. We examined key song attributes of the Kōkako to assess whether population size or growth rate are related to song complexity, the reduction of which may compromise effective communication. We analyzed song repertoire size and phrase-type sharing (i.e., Jaccard index of similarity), vocal performance (singing rates, song switching rates, and diversity of phrase types), and song syntactical characteristics (i.e., unpredictability in sequences of phrase types) in surviving and translocated populations (populations of approximately 19-250 territorial individuals). Population size was positively correlated with a population's song repertoire, song diversity, and switching of song phrase types and negatively correlated with shared phrase types and variation in syntactical structure of songs. Population growth rate correlated positively with pair repertoire size, population repertoire size, and singing rates during song bouts. As for solo-singing species in fragmented landscapes, songs in the fragmented populations of Kōkako appear to be undergoing microevolution as occurs in island colonization events. Our results suggest that vocal changes in small populations could affect population establishment and growth, particularly in multiple-source translocations. We believe measurement of vocal behavior could be used as a supplement to periodic population censuses to allow more frequent monitoring of population size.

Song characteristics vary clinally across an active colonization zone in Eurasian Nuthatches Sitta europaea

Capsule Eurasian Nuthatches have experienced a northward range expansion in Britain. Younger, more isolated, populations have smaller song meme-pool size, diversity and individual repertoires.

The effects of translocation‐induced isolation and fragmentation on the cultural evolution of bird song

Understanding the divergence of behavioural signals in isolated populations is critical to knowing how certain barriers to gene flow can develop. For many bird species, songs are essential for conspecific recognition and mate choice. Measuring the rate of song divergence in natural populations is difficult, but translocations of endangered birds to isolated islands for conservation purposes can yield insights, as the age and source of founder populations are completely known. We found significant and rapid evolution in the structure and diversity of bird song in North Island saddlebacks, Philesturnus rufusater, in New Zealand, with two distinct lineages evolving in < 50 years. The strong environmental filters of serial translocations resulted in cultural bottlenecks that generated drift and reduced song variability within islands. This rapid divergence coupled with loss of song diversity has important implications for the behavioural evolution of this species, demonstrating previously unrecognised biological consequences of conservation management.

Rattling cisticola song features and variability across sub‐Saharan Africa

AbstractQuantifying bird song variation can be an important tool for ensuring accurate species identification and can provide a significant basis for understanding the evolutionary processes that shape phenotypic diversity. This study describes variation in the songs of rattling cisticolas Cisticola chiniana across sub‐Saharan Africa. For many cisticola species, learned songs are the most obvious phenotypic indicators of species affiliation and may also function to indicate individual quality. We examined 957 songs recorded from 61 individuals and archived in sound libraries. To assess the diversity of syllable and song types, we examined patterns of syllable use. We also measured vocalization frequency and time parameters and assessed how they vary through space. Results indicated that rattling cisticola songs are highly variable, but also have features that are species‐specific. Examined songs had a relatively fixed structure containing one of three characteristic introductory note types, followed by an end phrase. Two of the introductory note types were sung across the species’ range (some 4500 km), whereas the third was only recorded in south‐western Africa. End phrases generated most of the diversity in songs and appeared to have an unlimited number of forms. End‐phrase characteristics showed a strong geographic variation, but did not vary with elevation. Song features varied individually and geographically in ways that are consistent with evolution due to multiple selective pressures, including stabilizing selection for species recognition on the introductory notes and diversifying selection on the end phrases. This pattern of lability in some song features coupled with stability in others may be a common feature of cisticola songs as it has also been found in Cisticola erythrops, a congener with a similarly broad range.

Birdsong Performance and the Evolution of Simple (Rather than Elaborate) Sexual Signals

Sexual signals are often elaborate as a result of sexual selection for signals of individual quality. Contrary to expectation, however, the elaboration of signals such as birdsong is not related to the strength of sexual selection across species. With a comparative study across wood warblers (family Parulidae), we show a compromise between advertising the performance of trills (syllable repetitions) and song complexity, which can result in the evolution of simple, rather than elaborate, song. Species with higher trill performance evolved simple songs with more extensive trilled syntax. This advertises trill performance but reduces syllable diversity in songs. These two traits are commonly sexually selected in songbirds, but indexes of sexual selection were not related to either in wood warblers. This is consistent with sexual selection targeting different traits in different species, sometimes resulting in simple signals. We conclude that the evolution of sexual signals can be unpredictable when their physiology affords multiple or, as here, opposing ways of advertising individual quality.

Comparative study on the song behavior and song control nuclei in male and female Mongolian larks (Melanocorypha mongolica)

Songbirds can produce a remarkable diversity of songs, which is well-characterized learned behavior that reflects the basic processes of language learning in humans. As song control nuclei governing song behavior has been identified, bird song provides an excellent model to address the relationship between brain areas and their controlling behavior. The Mongolian lark (Melanocorypha mongolica), a species of the Alaudidae family, is well known for its elaborate singing and ability to learn new songs, even in adulthood. Here, we studied the singing behavior and underlying neural structures of the Mongolian lark in both sexes. We found that the sizes of song bouts and song phrases (song repertoires) in male Mongolian larks are extremely large, and that each song repertoire or phrase has a complex structure, comprising several different syllables that seldom appear in other types of song bouts. In accordance with these complex songs, Mongolian lark song control nuclei are well developed and can be easily detected by Nissl staining. In contrast to male Mongolian larks, females were not observed to sing. However, they possess significant song control nuclei with abundant neural connectivity within them despite their small sizes compared with males. These data provide new evidence that help further clarify the mechanisms by which songbirds sing. Our results also have implications for the evolution of complex birdsongs and song control nuclei in oscine birds.

Song length variation serves multiple functions in the white-crowned sparrow

A wide variety of hypotheses has been proposed to explain the structural diversity in bird song repertoires. Song diversity is frequently described in terms of song “types” or within-type “variants.” Male Puget Sound white-crowned sparrows, Zonotrichia leucophrys pugetensis, produce variants of their single adult song type by altering the number of repetitions of syllables in the terminal trill. We tested whether variation in trill length correlated with distance to the receiver and with signaling context as predicted by the eavesdropping avoidance hypothesis and the strategic signaling hypothesis. In accordance with the eavesdropping avoidance hypothesis, males sang variants with shorter trills, and sang quieter and less frequently when near their mate during the incubation phase than during spontaneous singing while unpaired. Males also sang variants with short trills, but at a high rate and variable amplitude when within 10 m of an opponent during close male–male territorial interactions. In agreement with the strategic signaling hypothesis, males decreased trill length immediately before chasing an opponent, but did not change length consistently prior to flight. We conclude that the occurrence of short quiet songs sung near the mate agrees with predictions of the eavesdropping avoidance hypothesis, while short songs sung near other males are best explained by the strategic signaling hypothesis. Trill length variation may be a conventional signal of aggressive intentions in male–male contests stabilized by receiver-imposed retaliation costs.

A real-time method for autonomous passive acoustic detection-classification of humpback whales

This paper describes a method for real-time, autonomous, joint detection-classification of humpback whale vocalizations. The approach adapts the spectrogram correlation method used by Mellinger and Clark [J. Acoust. Soc. Am. 107, 3518-3529 (2000)] for bowhead whale endnote detection to the humpback whale problem. The objective is the implementation of a system to determine the presence or absence of humpback whales with passive acoustic methods and to perform this classification with low false alarm rate in real time. Multiple correlation kernels are used due to the diversity of humpback song. The approach also takes advantage of the fact that humpbacks tend to vocalize repeatedly for extended periods of time, and identification is declared only when multiple song units are detected within a fixed time interval. Humpback whale vocalizations from Alaska, Hawaii, and Stellwagen Bank were used to train the algorithm. It was then tested on independent data obtained off Kaena Point, Hawaii in February and March of 2009. Results show that the algorithm successfully classified humpback whales autonomously in real time, with a measured probability of correct classification in excess of 74% and a measured probability of false alarm below 1%.

Song Learning in Wild and Domesticated Strains of White‐Rumped Munia,Lonchura striata, Compared by Cross‐Fostering Procedures: Domestication Increases Song Variability by Decreasing Strain‐Specific Bias

AbstractSong diversity results from the interactions between natural selection, sexual selection, and individual learning. To understand song diversity, all three factors must be considered collectively, not separately. Bengalese Finches were domesticated about 250 yr ago. Their courtship songs have become different from their ancestor, the White‐rumped Munia. Bengalese Finches sing songs with complex note‐to‐note transition patterns and with acoustically diverse song notes while White‐rumped Munias sing songs with fixed note sequence and mostly broad band song notes. Bengalese Finches were selected for domestication based on their good parenting ability, not their songs, but this artificial selection has nonetheless affected their songs. To test whether divergence occurred not only in the song phenotypes but also in the genetic basis for predisposition of strain specific song learning, we conducted a cross‐fostering experiment between Bengalese Finches and White‐rumped Munias. In both strains, song learning was affected by rearing condition: the acoustical feature and transition patterns followed those of the foster fathers. However, the accuracy of song learning differed between the wild and the domesticated strains: sharing of song note between sons and tutors in Finches was not very accurate regardless of the tutor, while Munias were highly accurate in copying Munia songs but often omitted song elements from Finch fathers. These results suggest that White‐rumped Munias are strongly constrained to learn their own strain’s song, and that this constraint was relaxed in the Bengalese Finch by domestication.

Macrogeographical variation in the song of a widely distributed African warbler

The songs of oscine passerine birds vary on many spatial scales, reflecting the actions of diverse evolutionary pressures. Here we examine the songs of Cisticola erythrops, which effectively signal species identity across a geographical area spanning 6500 km in sub-Saharan Africa. Selection for species identification should promote stability in song traits, while sexual selection and geographical segregation should promote diversity. Cisticola erythrops share syllable types across the entire range of species and structure songs similarly, but individuals sing highly variable songs through improvisational recombination of syllables. Patterns of syllable use change gradually across the range of the species and do not show distinct breaks at subspecies boundaries. The acoustic properties of the most common syllable type also change gradually with distance. The results illustrate how songs can be simultaneously species-specific and highly variable at an individual level. At a larger level, patterns of variation indicate that cultural drift has generated song diversity through an isolation by distance mechanism.

Indian Blues: The Indigenization of American Popular Music

Indian Blues The Indigenization ofAmerican Popular Music Jo/m W. Troutman Native artists todayperform not onlyatpowwows butalso inrockand hip-hopclubs. Infact,American Indians have performed European andAfrican-derived musicfor centuries. Thefollowing essay revealsonefacet of thishistory, whenNative musicians turnedthe federalgovernment's"civilization" campaignon itshead, indigenizingthe music meant todetribalizethem. above The Navajo rock band Blackfire In 1955 anthropologist James Howard cast a dim light over the expressive culture of American Indians, remarking that powwows reflecta "process by which socio-cultural entities . . .are losing their tribaldistinctiveness and in its place are developing a nontribal Indian' culture."1 He believed thatAmerican Indian musical tradi tions were fast becoming generic, "pan-tribal" per formances that reflected a decreasing vitality and diversity of songs and dances. Any powwow sing er or dancer would immediately rejecthis analysis on the simple basis thattriballyspecific?and clan or family-specific?songs have vastly multiplied over thepast century, just as intertribalpowwow culture has proliferated to an extraordinary and quite heterogeneous degree. Yet equally profound in growth to powwow culture are theways in which American Indians have also manipulated 42 i World Literature Today Iand refiguredother formsofmusic, in theprocess developing new means within expressive culture toperform their identities as indigenous peoples. Just as the continued expanse of inter tribalpowwow culture has facilitated the sharing and development of new varieties of songs and dances, Native singers, musicians, and dancers of all varieties continue to access every available musical arena, including cyberspace. The Native American Music Awards, or "Nammys," are tell ing: they comprise over thirtygenres of music and provide awards ranging from best powwow and Native American Church recordings to best blues and hip-hop recordings. Indeed, many Native musicians have recognized popular music genres as opportunities to expand their tribal, oral traditions. For example, the 2008 Nammy Record of theYear award went to Blackfire's (Silence) Is a Weapon. The two-disc set is a tour de forceby these veteran "Alter-Native" and punk rockers from theDine Nation. They describe themselves on theirMySpace site as a "traditionally influ enced, high-energy, politically driven group com prised of two brothers and theirsister. Born into theheart of a political land dispute area on Black Mesa in the Navajo Nation, thisFamily's powerful music reflects the Hopes, Freedoms, and Barriers of today'sworld." Blackfire in facttours the world and has gained respect in many circles; their2002 album One Nation Under featured the last record ed vocals by punk legend Joey Ramone, and David Fricke, Rolling Stonemagazine's premier music critic,has promoted Blackfire in his col umns. (Silence) Is aWeapon consists of one disc of charging, protest rock-n-roll interlaced with Dine chants; the other disc is solely Dine ceremonial vocal and drum songs. Both discs suggest musi callywhat it means toBlackfire to beDine today, and the album demonstrates their extraordinary ability toweave thousands of years of ideas into one musical text. In effect, these artists have refig ured themeaning ofwhat constitutes their tribal, and indeed "Indian," music altogether. The practice by American Indians of fusing tribally derived music with that of Anglos and African Americans has existed for a very long time. Sacred music in missions and churches probably provided the first and certainly the longest-lasting variety of this blending of tradi tions, and the genres of American secular, popu larmusic have provided another. In the 1960s and 1970s, a number of Native musicians such as Cree singer Buffy Sainte-Marie, Kaw-Creek Saxophonist JimPepper, and Dakota singer Floyd Red Crow Westerman gained international fame for their rock, jazz, country, and folk recordings. These musicians and others gained an even high erprofile in the midst of theNative protestmove ments such as the takeover of Alcatraz Island, which captured the national media's attention at that time. Westerman's album Custer Died for Your Sins, for example, provided an equally scathing soundtrack forVine Deloria Jr/sgroundbreaking Nativepeoples forquite some timehad been blowing the saxophone, sawing the fiddle(or violin), and strumming guitars and mandolins. How theycame to those instruments and to these new styles ofmusic becomes particularly revealing when we considertheways in which thepracticeofmusic had become so divisively, politically charged in Indian Country inthe late nineteenth and early twentieth centuries. 1969 "Indian manifesto...

A distinct reed bunting dawn song and its relation to extrapair paternity

Elaborate birdsong is thought to have evolved under sexual selection. Extrapair mating can enforce sexual selection and thus the selection of song traits. We investigated song rate and song diversity, two song traits previously shown to be under sexual selection, in relation to paternity success in the reed bunting, Emberiza schoeniclus, a species with high levels of extrapair paternity. We focused our investigations on songs sung during the dawn chorus because singing at dawn is likely to be an honest signal and there is increasing evidence that females engage in extrapair copulations early in the morning. We classified a previously denoted continuous song, which is mainly sung during the dawn chorus, as a new song type in this species. Males with high song rate and high song diversity were more likely to gain extrapair paternity. These two song traits were also positively related to the number of extrapair offspring sired. However, most of the variance in extrapair paternity success was explained by age. Old males sired significantly more extrapair young than young males. Possibly, the new song type plays an important role in the female choice of extrapair mates. Reed bunting females may prefer males that sing at high rates and with high diversity because this indicates high phenotypic and genetic quality. Alternatively, these song parameters may be linked to other sexually selected traits or be important in the intersexual competition for extrapair fertilizations.

CHARACTERIZING THE SPATIAL STRUCTURE OF SONGBIRD CULTURES

Recent advances have shown that human-driven habitat transformations can affect the cultural attributes of animal populations in addition to their genetic integrity and dynamics. Here I propose using the song of oscine birds for identifying the cultural spatial structure of bird populations and highlighting critical thresholds associated with habitat fragmentation. I studied song variation over a wide geographical scale in a small and endangered passerine, the Dupont's Lark Chersophilus duponti, focusing on (1) cultural population structure, to determine a statistical representation of spatial variation in song and identify cultural units, and (2) the minimum patch size needed for an individual to develop a stable repertoire. I found that overall song diversity depends on variation among populations (beta-cultural diversity). Abrupt thresholds occurred in the relationships between individual song dissimilarity and geographic distance, and between individual song diversity and patch area. Spatial autocorrelation analysis showed that populations located as little as 5 km apart may have independently evolved their song traditions. Song diversity stabilized in patches as small as 100 ha supporting as few as 8-20 males. Song repertoires of smaller patches were significantly poorer. Almost one-quarter of the study populations inhabited patches <100 ha, and their cultural traditions appear to have eroded. The analysis of spatial patterns in birdsong may be a useful tool for detecting subpopulations prone to extinction.

Song Diversity Predicts the Viability of Fragmented Bird Populations

In the global scenario of increasing habitat fragmentation, finding appropriate indicators of population viability is a priority for conservation. We explored the potential of learned behaviours, specifically acoustic signals, to predict the persistence over time of fragmented bird populations. We found an association between male song diversity and the annual rate of population change, population productivity and population size, resulting in birds singing poor repertoires in populations more prone to extinction. This is the first demonstration that population viability can be predicted by a cultural trait (acquired via social learning). Our results emphasise that cultural attributes can reflect not only individual-level characteristics, but also the emergent population-level properties. This opens the way to the study of animal cultural diversity in the increasingly common human-altered landscapes.

Song Variation in a Recently Founded Population of the Dark‐Eyed Junco (Junco hyemalis)

AbstractDuring natural colonization events, songs are expected to change as a result of both selection and drift‐like processes. We studied song variation within a small isolated population of dark‐eyed juncos, Junco hyemalis, which became established in an unusual environment on the University of California at San Diego (UCSD) campus in the early 1980’s, and compared this variation with the native range. At UCSD, the average repertoire size is 4.2 song types/male, which is similar to that in the native range. There is a low level of song‐type sharing across the population. Typically a male shares at least one song type with on average 40% of his neighbors, and song‐type sharing decreases rapidly with distance. Thus song‐type diversity is high, and in this respect appears similar to that in ancestral mountain populations. These results suggest a moderate to large number of males founded and/or subsequently immigrated into the UCSD population, but several selection mechanisms, if coupled with a high cultural mutation rate, may also favor high song‐type diversity. When combined with results from a previous study, songs are significantly shorter at UCSD than in the mountain population we studied. It appears that founder effects have not influenced the evolution of songs in this population. More generally, if song‐type diversity and other features of song result from various social and natural selection pressures, many of these pressures may have remained similar between the native and the recently established population.

Folk Music from Wisconsin (review)

Reviewed by: Folk Music from Wisconsin James P. Leary Folk Music from Wisconsin. [1960] 2001. Compiled and annotated by Helene Stratman-Thomas; reissue produced by Bob Carlin. American Folklife Center, Library of Congress, in cooperation with Rounder Records, CD (1), Rounder 1521. Folk Music from Wisconsin, once available only as an LP in a plain but durable record jacket stuffed with a stapled typescript, is now in a far more attractive package, thanks to the American Folklife Center's joint venture with Rounder Records to reissue titles from the old Folk Music of the United States series of the Archive of Folk Culture at the Library of Congress. The twenty-one tracks, remastered for excellent sound, are culled from the 1940s field recordings of Helene Stratman-Thomas, a faculty member in the School of Music at the University of Wisconsin. With the exception of two pages devoted to credits and a historical sketch of the Archive of Folk Culture, the text of the thirty-eight-page booklet faithfully reproduces Stratman-Thomas's fine original notes, including the places and dates of recordings, performers' biographies, comparative discussions of songs and tunes, song lyrics, references, and a bibliography. The new booklet adds eleven photographs, most of them portraits of performers made during Stratman-Thomas's 1941 and 1946 forays around Wisconsin. In keeping with the high degree of cultural pluralism that has characterized Wisconsin since the early nineteenth century, Stratman-Thomas did fieldwork with nearly thirty ethnic groups, recording Ho-Chunk morning songs, Luxembourger immigrant ballads, Walloon dance tunes, Swiss yodels, French singing games, Polish highlander fiddling, and much more—over seven hundred performances altogether. This production, however, includes "only ballads and songs in the English tongue" (p. 1), an indication of both the antiforeign, assimilationist ideology dominating American public culture and the prevailing Anglophile orientation of American folksong scholarship at the time of its initial release. Regrettable limitations aside, we hear fine versions of nine ballads concerning tarrying nobles ("Lord Lovel," Child 75), Irish robbers ("Brennan on the Moor," Laws L7), suffering sweethearts ("Charming Beauty Bright," Laws M6, and "The Drowsy Sleeper," Laws M4), faithful lovers ("The Lake of Ponchartrain," Laws H9), valiant cowboys ("Billy Vanero," Laws B6), snake-bit farmhands ("Springfield Mountain," Laws G16), disaster victims ("Milwaukee Fire," Laws G15), and contesting lumberjacks ("Little Brown Bulls," Laws C16). The last two, as well as Eben Rexford's composition, "The Ride of Paul Venarez" (the source of "Billy Vanero"), originated in Wisconsin. Lyric folksongs include a children's singing game ("Pompey is Dead") and a fox hunter's ditty ("How Happy is the Sportsman"); the Irish "Shule Aroon"; two celebrations of lumber camps and woods workers ("Shantyman's Life," "The Bold McIntyres"); a harvesters' anthem ("The Cranberry Song"); and a cante-fable spread by traveling shills for Hamlin's Wizard Oil ("Reuben Wright and Phoebe Brown"). The foregoing sixteen performances, seven by women and nine by men, are all unaccompanied, with the exception of Luther Royce's guitar-backed rendition of "Billy Vanero." Royce's twangy, rather than crooning, emulation of singing cowboys like Jules Verne Allen is paralleled in its vernacular culture orientation by Hamilton Lobdell's Wizard Oil campiness. The other singers rely variously on the folk styles of Cornish, English, Irish, and Welsh immigrants; Yankees and Yorkers; and the "Kentucks" who settled in northern Wisconsin in [End Page 76] the 1890s. The haunting lilt of Antigo's Pearl Jacobs Borusky, a "Kentuck" from a singing family, and the Irish-derived woods singing of Rhinelander's Emery DeNoyer are particularly stellar. They may also be heard singing "The Rich Old Farmer" and "The Little Brown Bulls," respectively, on Anglo American Ballads (Rounder 1511). Pearl Jacobs Borusky's marriage into an extended Polish family and the acquisition of Irish American performance mannerisms by the French Canadian DeNoyer hint at the broader linguistic and cultural diversity of vocal styles and songs prevailing in Wisconsin in the 1940s. Although we hear none of that diversity on Folk Music from Wisconsin, we are treated to five highly creolized "lumber camp" tunes performed by Iva and Otto Rindlisbacher of Rice Lake. The children of Swiss German immigrants, the Rindlisbachers were adept players of Swiss...

REGIONAL SEISMIC SONG DIFFERENCES IN SKY ISLAND POPULATIONS OF THE JUMPING SPIDER HABRONATTUS PUGILLIS GRISWOLD (ARANEAE, SALTICIDAE)

Jumping spiders have long been used as model organisms to study visual communication. However, recent studies documenting the presence of intricate multicomponent seismic songs during court- ship displays suggest an important role of seismic communication as well. Given the relatively recent focus on seismic communication, the extent to which seismic songs vary among jumping spider species or even among populations remains poorly understood. Here, we use the extensively studied Habronattus pugillis Griswold 1987 complex to explore putative seismic song diversity among males from isolated populations. H. pugillis populations have been studied extensively because of the tremendous diversifi- cation of male visual secondary sexual ornaments observed among adjacent mountain-top populations in southeastern Arizona (''sky islands''). Here, we aim to explore putative parallel patterns of diversification in seismic courtship songs between different sky island populations. Using laser vibrometry, we examined in detail the songs of three mountaintop populations (Atascosa (AT), Santa Rita (SR), and Santa Catalina (SC)) and observed an extraordinary diversity of songs and song types among these three populations. Large differences were seen in both the temporal and spectral properties of male seismic songs. In addition, we observed differences in song complexity between populations with some populations having ''simple'' songs (1 component) and others having ''complex'' songs (3 components). We also present preliminary data from four additional populations (Galiuro (GA), Huachuca (HU), Mule (MU), and Patagonia (PA)). Results from this study suggest that the diversification of male visual signals observed among populations of H. pugillis finds a counterpart in male seismic songs

Extrapair paternity in chestnut-sided warblers is correlated with consistent vocal performance

The elaborateness of many bird songs is commonly presumed to have evolved under the influence of sexual selection by female mate choice. Thus, aspects of acoustic diversity, such as song repertoire size, are seen as likely targets of female choice. In many songbird species with song repertoires, however, the repertoires are small. In such species, female choice might be based on song features other than, or in addition to, song diversity. To investigate this conjecture, I assessed singing and paternity in a population of chestnut-sided warblers (Dendroica pensylvanica), a species in which song repertoires are of modest size. Twenty-two song traits were evaluated to determine which ones best predicted male extrapair reproductive success. The candidate traits encompassed measures of song diversity (e.g., song repertoire size), gross-scale song performance (e.g., singing rate), and fine-scale song performance (e.g., variability among songs in a bout). Regression analysis revealed that the best predictor of extrapair success was singing with little variability. In particular, the most successful males sang with consistent pitch and timing, as well as high pitch. The greater extrapair success of males with more consistent vocal performance may be due to female preference for such performance, which could be an indicator of male quality. Copyright 2007.

Song repertoire size is correlated with body measures and arrival date in common nightingales, Luscinia megarhynchos

In songbirds, the individual features of a male's song play a role in female choice and male–male interactions. Therefore, it has been hypothesized that the song characteristics of an individual should be correlated with its quality and this has been shown for some species. The species studied so far have only small or medium-sized song repertoires, leaving open the question of whether, in species with large repertoires, song characteristics such as repertoire size are related to male quality. We investigated the correlations between body measures, song characteristics and arrival dates of common nightingales, a songbird species in which males have extraordinarily large song type repertoires. We found that birds with large repertoires had longer wings and were heavier, and arrived earlier, than those with small repertoires. Other song characteristics, such as song diversity and proportion of whistle songs, were not significantly correlated with body measures. When we correlated body measures with arrival date, we found that birds that arrived earlier were heavier and tended to be in better condition. These findings provide supporting evidence that repertoire size is an indicator of a male's quality.

Narishige Zoological Science Symposium: From Sensory Reception, Behavior to Brain Functions: Neuroscience in Invertebrates

Cricket calling song is a species-specific signal and plays an important role in species recognition. The role of cricket song as a pre-mating isolation mechanism should be examined in a comparative study of closely related species inhabit sympatrically. On the Japanese Archipelago, three Teleogryllus species have wide distribution areas. T. yezoemma ranges from Hokkaido Island to the Kanto region, T. emma from Hokkaido to the Kyushu region, and T. taiwanemma from south of the Kii Peninsula to the South Asian tropics. The distribution of T. emma overlaps that of T. yezoemma in the north and that of T. taiwanemma in the south. T. yezoemma and T. taiwanemma are allopatric. I compared calling songs of the three species using principal component analysis. Furthermore, three-choice playback experiments using females of the three Teleogryllus species were performed to test whether female crickets can discriminate accurately their conspecific mates on the basis of their calling song. The results showed that the allopatric species (T. yezoemma and T. taiwanemma) have similar songs that females cannot discriminate accurately, whereas the partially sympatric species (T. yezoemma and T. emma, T. emma and T. taiwanemma) have divergent songs that females can distinguish accurately. This empirical evidence suggests that calling song plays an important role as a pre-mating isolation mechanism in three species of Teleogryllus. Furthermore, I performed three-choice playback experiments for females of each species using a synthetic song in order to identify the key feature for mate choice. The results showed that females preferred the song with the conspecific pulse period, while did not show a clear preference for dominant frequency. For pulse number and inter-phrase duration, females showed open-ended preference. These results suggest that pulse period is the key feature for species-specific song recognition. Studies of acoustic animal communication have shown that temporal patterns are more important than frequency parameters for song recognition. Previous neurophysiological studies of other cricket species support these results. In addition, there were differences in female preference shape among the three species. This suggests that even closely related species evaluate key features differently, and consequently calling song diversity could have appeared in the evolutionary process.