Seasonal Song Research Articles

Spring-Time Ritual Folk Songs from Zvenyhorodshchyna: Ethnography, Typology, Geography

Spring-time ritual folk songs are currently a relict phenomenon in the local tradition of the historical Zvenyhorodka region (which covers the current Zvenyhorodka and parts of the neighbouring regions of the Right Bank of Cherkasy region) studies, so each recorded unit (song, text, description of a ritual or even a mention of their former life) is perceived by the researcher as an very important finding.
 In the Eastern Podillia region of Cherkasy region (on the lands of the historical Uman region) until recently, you could hear stories about the rituals and songs of the spring-time cycle. On the other hand, spring-time melotypes are almost completely absent in the Naddnipryanshchyna villages (except for Nadtyasmynnia area). In this way, Zvenyhorodshchyna appears as the frontier of the actual ritual folk songs certain layer existence and at the same time – a transition zone between two large ethnographic regions, which absorbed the musical and stylistic features of both of them.
 In the most complete collection of calendar and family rituals of the Right Bank of Cherkasy region, the beginning of the 20th century – monograph "Zvenyhorodshchyna" by A. Krymskyi, in addition to a detailed description of customs, rites and comments on them, contains more than 40 texts of spring dances, games and songs, as well as fasting verbal verses – "khrystuvannia", performed during the round of courtyards by children and young people on Easter. A certain number of samples of spring-time ritual genres are also found in music and ethnographic publications of different years and in the author's contemporary recordings.
 The largest part of the local spring repertoire is made up of round dance and dance songs: "Shum", "Kryvyi Tanec", "Mak", "Zaichyk", "Proso", "Podolyanochka", "Verbovaya Kladochka", "Tuman", etc. Spring dances begin to be led and sung from Easter or even during Lent.
 Among the genres of spring-time ritual singing, there are unique examples of early spring appeals, a group of lyrical ("velychalni" according to Y. Yefremov) ("Oh vesna, vesna, vesnyanochka", "Oi u pravuyu seredu", etc.) and timed ones to the spring season songs.
 The collected and analyzed musical and ethnographic data formed the basis of typological maps that allow us to draw conclusions about the geographical distribution of certain spring melotypes in the Zvenyhorodshchyna region.

Seasonal song ontogeny in western North Atlantic humpback whales: drawing parallels with songbirds

ABSTRACT The use of song as a reproductive display is common in the animal kingdom; however, for many taxa, little is known of song ontogeny. Male humpback whales produce elaborate songs on low latitude breeding grounds in winter and begin to sing on high latitude feeding grounds in late summer, yet songs from the two locations are rarely compared. Seasonal song ontogeny in western North Atlantic humpback whales was explored by comparing songs recorded in high latitude feeding grounds (Canada in spring 2016 and fall 2016 to winter 2017) with songs recorded in a low latitude breeding ground (Dominican Republic in winter and spring 2017). High-quality song samples were selected, and every phrase annotated. Song theme order, song duration, and number of phrase repetitions were compared across samples. The most variability in theme order was found between November and December in the Canadian recordings, a phase in song ontogeny that may be important for learning. Song duration gradually increased, via an increase in phrase repetitions, through the breeding season, before peaking in the Dominican Republic between January and March. A comparison to oscine bird seasonal song ontogeny revealed many similarities, highlighting potentially similar physiological processes between humpback whales and songbirds.

Seasonal song variation in male Carolina Wrens (Thryothorus ludovicianus)

Birdsong's primary function is attracting and stimulating mates and repelling rivals during the breeding season. However, many species also sing during the nonbreeding season, which raises questions about the function of nonbreeding season song and the mechanisms underlying its production. In this study, we compared spectral and temporal measurements from a large sample of breeding (N=267) and nonbreeding season songs (N=283) of the Carolina Wren (Thryothorus ludovicianus), a nonmigratory, temperate species that sings year round. We found that breeding season songs were longer than nonbreeding season songs and had more syllables within each song. Trill rate, the number of notes per syllable, minimum and maximum frequency, and frequency bandwidth did not differ detectably between the 2 seasons. This study is the first to examine seasonal song differences in Carolina Wrens and provides a basis for future investigations into the drivers behind this seasonal variation.

Unilateral vocal nerve resection alters neurogenesis in the avian song system in a region-specific manner.

New neurons born in the adult brain undergo a critical period soon after migration to their site of incorporation. During this time, the behavior of the animal may influence the survival or culling of these cells. In the songbird song system, earlier work suggested that adult-born neurons may be retained in the song motor pathway nucleus HVC with respect to motor progression toward a target song during juvenile song learning, seasonal song restructuring, and experimentally manipulated song variability. However, it is not known whether the quality of song per se, without progressive improvement, may also influence new neuron survival. To test this idea, we experimentally altered song acoustic structure by unilateral denervation of the syrinx, causing a poor quality song. We found no effect of aberrant song on numbers of new neurons in HVC, suggesting that song quality does not influence new neuron culling in this region. However, aberrant song resulted in the loss of left-side dominance in new neurons in the auditory region caudomedial nidopallium (NCM), and a bilateral decrease in new neurons in the basal ganglia nucleus Area X. Thus new neuron culling may be influenced by behavioral feedback in accordance with the function of new neurons within that region. We propose that studying the effects of singing behaviors on new neurons across multiple brain regions that differentially subserve singing may give rise to general rules underlying the regulation of new neuron survival across taxa and brain regions more broadly.

Neuroendocrine patterns underlying seasonal song and year-round territoriality in male black redstarts

BackgroundThe connection between testosterone and territoriality in free-living songbirds has been well studied in a reproductive context, but less so outside the breeding season. To assess the effects of seasonal androgenic action on territorial behavior, we analyzed vocal and non-vocal territorial behavior in response to simulated territorial intrusions (STIs) during three life-cycle stages in free-living male black redstarts: breeding, molt and nonbreeding. Concurrently, we measured changes in circulating testosterone levels, as well as the mRNA expression of androgen and estrogen receptors and aromatase in the preoptic, hypothalamic and song control brain areas that are associated with social and vocal behaviors.ResultsTerritorial behavior and estrogen receptor expression in hypothalamic areas did not differ between stages. But plasma testosterone was higher during breeding than during the other stages, similar to androgen receptor and aromatase expression in the preoptic area. The expression of androgen receptors in the song control nucleus HVC was lower during molt when birds do not sing or sing rarely, but similar between the breeding and the nonbreeding stage. Nevertheless, some song spectral features and the song repertoire differed between breeding and nonbreeding. Territorial behavior and song rate correlated with the expression of steroid receptors in hypothalamic areas, and in the song control nucleus lMAN.ConclusionsOur results demonstrate seasonal modulation of song, circulating testosterone levels, and brain sensitivity to androgens, but a year-round persistency of territorial behavior and estrogen receptor expression in all life-cycle stages. This suggests that seasonal variations in circulating testosterone concentrations and brain sensitivity to androgens is widely uncoupled from territorial behavior and song activity but might still affect song pattern. Our study contributes to the understanding of the complex comparative neuroendocrinology of song birds in the wild.

Humpback whale song occurrence reflects ecosystem variability in feeding and migratory habitat of the northeast Pacific.

This study examines the occurrence of humpback whale (Megaptera novaeangliae) song in the northeast Pacific from three years of continuous recordings off central California (36.713°N, 122.186°W). Song is prevalent in this feeding and migratory habitat, spanning nine months of the year (September–May), peaking in winter (November–January), and reaching a maximum of 86% temporal coverage (during November 2017). From the rise of song in fall through the end of peak occurrence in winter, song length increases significantly from month to month. The seasonal peak in song coincides with the seasonal trough in day length and sighting-based evidence of whales leaving Monterey Bay, consistent with seasonal migration. During the seasonal song peak, diel variation shows maximum occurrence at night (69% of the time), decreasing during dawn and dusk (52%), and further decreasing with increasing solar elevation during the day, reaching a minimum near solar noon (30%). Song occurrence increased 44% and 55% between successive years. Sighting data within the acoustic detection range of the hydrophone indicate that variation in local population density was an unlikely cause of this large interannual variation. Hydrographic data and modeling of acoustic transmission indicate that changes in neither habitat occupancy nor acoustic transmission were probable causes. Conversely, the positive interannual trend in song paralleled major ecosystem variations, including similarly large positive trends in wind-driven upwelling, primary productivity, and krill abundance. Further, the lowest song occurrence during the first year coincided with anomalously warm ocean temperatures and an extremely toxic harmful algal bloom that affected whales and other marine mammals in the region. These major ecosystem variations may have influenced the health and behavior of humpback whales during the study period.

Literate Shamanism: The Priests Called Then among the Tày in Guangxi and Northern Vietnam

Then is the designation in Vietnamese and Tày given to shamanic practitioners of the Tày ethnicity, who reside mainly in the northern provinces of Vietnam. Scholars are long aware that the predominantly female spirit mediums among the Zhuang in Guangxi, variously called mehmoed or mehgimq, had a ritual repertoire which included shamanic journeys up to the sky as their essential element. The ritual songs of the mehmoed are orally transmitted, unlike the rituals of male religious practitioners in Guangxi such as Taoist priests, Ritual Masters, and mogong, all of which are text-based. One was led rather easily to posit a dichotomy in which male performers had texts, and female performers had repertoires which were orally transmitted. This division also seemed to hold true for certain seasonal song genres, at least in Guangxi. For that matter, shamanic traditions cross-culturally are seen as predominantly or exclusively oral traditions. Recent research among the Tày-speaking communities in northern Vietnam has confounded this tidy picture. Religious practitioners among the Tày include the Pụt, who in many cases have texts which incorporate segments of shamanic sky journeys and may be either male or female; and the Then, also both male and female, who have extensive repertoires of shamanic rituals which are performed and transmitted textually. The Then have a performance style that is recognisably based on shamanic journeying, but elaborated as a form of art song, complete with instrumental accompaniment (two- or three-stringed lutes), ritual dances, and flamboyant costumes. Apart from individual performances, there are large-scale rituals conducted by as many as a dozen priests. The present paper gives an overview of the practices and rituals of the Then, based on recent fieldwork in Vietnam and Guangxi, and discusses the implications these have for our conventional understandings of shamanism, literacy, gender, and the cultural geography of the border regions.

Seasonal plasticity of song behavior relies on motor and syntactic variability induced by a basal ganglia–forebrain circuit

The plasticity of nervous systems allows animals to quickly adapt to a changing environment. In particular, seasonal plasticity of brain structure and behavior is often critical to survival or mating in seasonal climates. Songbirds provide striking examples of seasonal changes in neural circuits and vocal behavior and have emerged as a leading model for adult brain plasticity. While seasonal plasticity and the well-characterized process of juvenile song learning may share common neural mechanisms, the extent of their similarity remains unclear. Especially, it is unknown whether the basal ganglia (BG)–forebrain loop which implements song learning in juveniles by driving vocal exploration participates in seasonal plasticity. To address this issue, we performed bilateral lesions of the output structure of the song-related BG–forebrain circuit (the magnocellular nucleus of the anterior nidopallium) in canaries during the breeding season, when song is most stereotyped, and just after resuming singing in early fall, when canaries sing their most variable songs and may produce new syllable types. Lesions drastically reduced song acoustic variability, increased song and phrase duration, and decreased syntax variability in early fall, reverting at least partially seasonal changes observed between the breeding season and early fall. On the contrary, lesions did not affect singing behavior during the breeding season. Our results therefore indicate that the BG–forebrain pathway introduces acoustic and syntactic variability in song when canaries resume singing in early fall. We propose that BG–forebrain circuits actively participate in seasonal plasticity by injecting variability in behavior during non-breeding season. Significance StatementThe study of seasonal plasticity in temperate songbirds has provided important insights into the mechanisms of structural and functional plasticity in the central nervous system. The precise function and mechanisms of seasonal song plasticity however remain poorly understood. We show here that a basal ganglia–forebrain circuit involved in the acquisition and maintenance of birdsong is actively inducing song variability outside the breeding season, when singing is most variable, while having little effect on the stereotyped singing during the breeding season. Our results suggest that seasonal plasticity reflects an active song-maintenance process akin to juvenile learning, and that basal ganglia–forebrain circuits can drive plasticity in a learned vocal behavior during the non–injury-induced degeneration and reconstruction of the neural circuit underlying its production.

Dominance-related seasonal song production is unrelated to circulating testosterone in a subtropical songbird

Circulating testosterone (T) is widely considered to play a key role in the production of sexual displays by male vertebrates. While numerous studies support a role for circulating T in promoting the production of song in male birds, this understanding is based primarily on evidence from seasonally breeding northern temperate species, leaving it unclear whether this mechanism generalizes to other regions of the world. Here we investigate whether variation in circulating levels of T can explain the marked within- and among-individual variation in male song performance observed in a subtropical population of the year-round territorial white-browed sparrow weaver (Plocepasser mahali mahali). Our findings reveal that both circulating T and male song production peaked at a similar time point, halfway through the population-level breeding season. However, while dominant males were more likely to sing and sang for longer than subordinate males, within-group paired comparisons revealed no dominance-related differences in circulating T. Moreover, comparisons both among and within individual dominant males revealed that song duration, syllable rate and proportion of time spent singing were all unrelated to circulating T. Together, our findings suggest that natural variation in male song production, at least in this population of white-browed sparrow weavers, is achieved principally through mechanisms other than variation in circulating T concentration. More widely, our results are in line with the view that male song production is not exclusively regulated by gonadally synthesized steroids.

Dawn-song onset coincides with increased HVC androgen receptor expression but is decoupled from high circulating testosterone in an equatorial songbird

The song of songbirds is a testosterone-sensitive behavior that is controlled by brain regions expressing androgen receptors. At higher latitudes, seasonal singing is stimulated by increasing day-length and elevated circulating testosterone. However, a large number of songbird species inhabit equatorial regions under a nearly constant photoperiod, and the neuroendocrine mechanisms of seasonal song in these species have rarely been investigated. We studied males from an equatorial population of the silver-beaked tanager (Ramphocelus carbo), an Amazonian songbird. We found seasonality in dawn-song behavior, which was displayed continuously for more than half a year throughout an extended breeding territoriality stage. The seasonal activation of dawn-song was correlated with an increased area of androgen receptor expression in HVC, a major brain area of song control. However, testosterone levels remained low for several weeks after activation of dawn-song. Circulating levels of testosterone were elevated only later in the breeding season, coinciding with a higher dawn-song output and with the mating period. Our results suggest that the seasonal activation of dawn-song and territoriality involves an increase of androgen target cells in HVC. This mechanism could potentially function to circumvent adverse effects of high testosterone levels in a species with an extended breeding season.

Semantic Fields in Selected Poems from "Season Songs" by Ted Hughes

Ted Hughes (1930–1998), the Poet Laureate (1984–1998) wrote a collection entitled Season Songs, originally intended for child audience. Analysis of the obvious semantic fields in three selected poems from the collection shows that the poems possess more than the aspects intended for children – alongside observation of the season and nature, they point also at transcendent values and experiences beyond and outside childhood.

Using the canary genome to decipher the evolution of hormone-sensitive gene regulation in seasonal singing birds.

BackgroundWhile the song of all songbirds is controlled by the same neural circuit, the hormone dependence of singing behavior varies greatly between species. For this reason, songbirds are ideal organisms to study ultimate and proximate mechanisms of hormone-dependent behavior and neuronal plasticity.ResultsWe present the high quality assembly and annotation of a female 1.2-Gbp canary genome. Whole genome alignments between the canary and 13 genomes throughout the bird taxa show a much-conserved synteny, whereas at the single-base resolution there are considerable species differences. These differences impact small sequence motifs like transcription factor binding sites such as estrogen response elements and androgen response elements. To relate these species-specific response elements to the hormone-sensitivity of the canary singing behavior, we identify seasonal testosterone-sensitive transcriptomes of major song-related brain regions, HVC and RA, and find the seasonal gene networks related to neuronal differentiation only in the HVC. Testosterone-sensitive up-regulated gene networks of HVC of singing males concerned neuronal differentiation. Among the testosterone-regulated genes of canary HVC, 20% lack estrogen response elements and 4 to 8% lack androgen response elements in orthologous promoters in the zebra finch.ConclusionsThe canary genome sequence and complementary expression analysis reveal intra-regional evolutionary changes in a multi-regional neural circuit controlling seasonal singing behavior and identify gene evolution related to the hormone-sensitivity of this seasonal singing behavior. Such genes that are testosterone- and estrogen-sensitive specifically in the canary and that are involved in rewiring of neurons might be crucial for seasonal re-differentiation of HVC underlying seasonal song patterning.Electronic supplementary materialThe online version of this article (doi:10.1186/s13059-014-0578-9) contains supplementary material, which is available to authorized users.

The function of seasonal song in a tropical resident species, the Red-throated Ant-tanager (Habia fuscicauda)

Recent studies of tropical birds with year-round territoriality indicate that song rate is relatively low year-round in association with lower seasonality and relatively stable social environment over the year. We examined seasonal variation in the song rate of Red-throated Ant-tanagers (Habia fuscicauda), a socially monogamous species in which males predominantly sing during the breeding season, to determine to what extent increased song rate is driven by (1) increased territory defense, (2) pair coordination of nest initiation, and (3) competition for extra-pair mating opportunities. Song was infrequent during the non-breeding season, increased dramatically prior to nesting (17 % time spent singing), and increased even more so during nesting (32 % time spent singing). Male song output was inversely related to frequency of interactions between pairs at territorial borders; however, interactions may also serve in a mating context. Extra-pair matings were common, and 17 of 41 nestlings in ten of 19 broods were extra-pair young, suggesting that high male song output may be sexually selected via extra-pair mate choice. Although males spent much less time singing prior to nesting, our results also indicate that male initiation of singing was associated with female egg-laying date, indicating also a role in within-pair coordination of reproduction. Our results suggest that high song output during the breeding season may be more common in omnivorous species that experience increased seasonality and that it may be indicative of an extra-pair mating system. More studies of species with diverse life histories are needed to examine the ecological conditions that explain interspecific variation in song output.

Regulatory mechanisms of testosterone-stimulated song in the sensorimotor nucleus HVC of female songbirds

BackgroundIn male birds, influence of the sex steroid hormone testosterone and its estrogenic metabolites on seasonal song behavior has been demonstrated for many species. In contrast, female song was only recently recognized to be widespread among songbird species, and to date, sex hormone effects on singing and brain regions controlling song development and production (song control nuclei) have been studied in females almost exclusively using domesticated canaries (Serinus canaria). However, domesticated female canaries hardly sing at all in normal circumstances and exhibit only very weak, if any, song seasonally under the natural photoperiod. By contrast, adult female European robins (Erithacus rubecula) routinely sing during the winter season, a time when they defend feeding territories and show elevated circulating testosterone levels. We therefore used wild female European robins captured in the fall to examine the effects of testosterone administration on song as well as on the anatomy and the transcriptome of the song control nucleus HVC (sic). The results obtained from female robins were compared to outcomes of a similar experiment done in female domesticated canaries.ResultsTestosterone treatment induced abundant song in female robins. Examination of HVC transcriptomes and histological analyses of song control nuclei showed testosterone-induced differentiation processes related to neuron growth and spacing, angiogenesis and neuron projection morphogenesis. Similar effects were found in female canaries treated with testosterone. In contrast, the expression of genes related to synaptic transmission was not enhanced in the HVC of testosterone treated female robins but was strongly up-regulated in female canaries. A comparison of the testosterone-stimulated transcriptomes indicated that brain-derived neurotrophic factor (BDNF) likely functions as a common mediator of the testosterone effects in HVC.ConclusionsTestosterone-induced singing of female robins correlated with cellular differentiation processes in the HVC that were partially similar to those seen in the HVC of testosterone-treated female canaries. Other modes of testosterone action, notably related to synaptic transmission, appeared to be regulated in a more species-specific manner in the female HVC. Divergent effects of testosterone on the HVC of different species might be related to differences between species in regulatory mechanisms of the singing behavior.Electronic supplementary materialThe online version of this article (doi:10.1186/s12868-014-0128-0) contains supplementary material, which is available to authorized users.

The role of the pineal gland in the photoperiodic control of bird song frequency and repertoire in the house sparrow, Passer domesticus

Temperate zone birds are highly seasonal in many aspects of their physiology. In mammals, but not in birds, the pineal gland is an important component regulating seasonal patterns of primary gonadal functions. Pineal melatonin in birds instead affects seasonal changes in brain song control structures, suggesting the pineal gland regulates seasonal song behavior. The present study tests the hypothesis that the pineal gland transduces photoperiodic information to the control of seasonal song behavior to synchronize this important behavior to the appropriate phenology. House sparrows, Passer domesticus, expressed a rich array of vocalizations ranging from calls to multisyllabic songs and motifs of songs that varied under a regimen of different photoperiodic conditions that were simulated at different times of year. Control (SHAM) birds exhibited increases in song behavior when they were experimentally transferred from short days, simulating winter, to equinoctial and long days, simulating summer, and decreased vocalization when they were transferred back to short days. When maintained in long days for longer periods, the birds became reproductively photorefractory as measured by the yellowing of the birds' bills; however, song behavior persisted in the SHAM birds, suggesting a dissociation of reproduction from the song functions. Pinealectomized (PINX) birds expressed larger, more rapid increases in daily vocal rate and song repertoire size than did the SHAM birds during the long summer days. These increases gradually declined upon the extension of the long days and did not respond to the transfer to short days as was observed in the SHAM birds, suggesting that the pineal gland conveys photoperiodic information to the vocal control system, which in turn regulates song behavior.

Testosterone-dependency of male solo song in a duetting songbird — Evidence from females

For male songbirds of the temperate zone there is a tight link between seasonal song behaviour and circulating testosterone levels. Such a relationship does not seem to hold for tropical species where singing can occur year-round and breeding seasons are often extended. White-browed sparrow weavers (Plocepasser mahali) are cooperatively breeding songbirds with a dominant breeding pair and male and female subordinates found in eastern and southern Africa. Each group defends an all-purpose territory year-round. While all group members sing duets and choruses, the most dominant male additionally sings a solo song that comprises a distinct and large syllable repertoire. Previous studies suggested this type of song being associated with reproduction but failed to support a relationship with males' circulating testosterone levels. The present study aimed to investigate the steroid hormone sensitivity of the solo song in more detail. We found that dominant males had significantly higher circulating testosterone levels than subordinates during the early and late breeding seasons. No changes in solo song characteristics were found between both time points. Further, experimental implantation of captive adult females with exogenous testosterone induced solo singing within one week of treatment. Such females produced male-typical song regarding overall structure and syllable composition. Sex differences existed, however, concerning singing activity, repertoire size and temporal organisation of song. These results suggest that solo singing in white-browed sparrow weavers is under the control of gonadal steroid hormones. Moreover, the behaviour is not male-specific but can be activated in females under certain conditions.

Ted Hughes: The Development of a Children’s Poet

This article looks at how Ted Hughes’ poetry for children developed over more than 30 years of publication. It traces the movement from his earlier, more conventional rhyming poems, such as Meet My Folks! (1961) and Nessie the Mannerless Monster (1964), to the mature, free verse “animal poems” for older readers of Season Songs (1976c), Under the North Star (1981) and the “farmyard fable” What is the Truth? (1984). The article argues that the later lyrical poems for younger readers where Hughes returned to rhyme, The Cat and the Cuckoo (1987) and The Mermaid’s Purse (1993), represent an undervalued final phase of Hughes’ work for children which is rarely discussed by critics. The discussion considers Hughes’ changing attitude to the concept of the “children’s poet” at different periods of his career. Reference is made throughout to Hughes’ own writing about children and poetry, such as Poetry in the Making (1967), and to parallel developments in his poetry for adults.

Ted Hughes: a literary life

Acknowledgements Introduction Formation and Juvenilia 'The Thought-Fox': Hughes and Cambridge The Encounter with Sylvia Plath Dreaming from America: Lupercal Wodwo : the 'Single Adventure' and the Death of Sylvia Plath The Making of Crow The 'Plath Wars' The Shaman-Poet and Masculine Guilt: Gaudete and Cave Birds Farmer Hughes: Moortown Diary and Season Songs Return to the Calder Valley: Remains of Elmet, Wolfwatching and Elmet Fisherman Hughes: River The Poet Laureate Writing for Children Hughes as Translator Mourning Plath: Birthday Letters Epilogue Select Bibliography Index

Androgens and estrogens induce seasonal-like growth of song nuclei in the adult songbird brain.

In seasonally breeding songbirds, the brain regions that control song behavior undergo dramatic structural changes at the onset of each annual breeding season. As spring approaches and days get longer, gonadal testosterone (T) secretion increases and triggers the growth of several song control nuclei. T can be converted to androgenic and estrogenic metabolites by enzymes expressed in the brain. This opens the possibility that the effects of T may be mediated via the androgen receptor, the estrogen receptor, or both. To test this hypothesis, we examined the effects of two bioactive T metabolites on song nucleus growth and song behavior in adult male white-crowned sparrows. Castrated sparrows with regressed song control nuclei were implanted with silastic capsules containing either crystalline T, 5alpha-dihydrotestosterone (DHT), estradiol (E(2)), or a combination of DHT+E(2). Control animals received empty implants. Song production was highly variable within treatment groups. Only one of seven birds treated with E(2) alone was observed singing, whereas a majority of birds with T or DHT sang. After 37 days of exposure to sex steroids, we measured the volumes of the forebrain song nucleus HVc, the robust nucleus of the archistriatum (RA), and a basal ganglia homolog (area X). All three steroid treatments increased the volumes of these three song nuclei when compared to blank-implanted controls. These data demonstrate that androgen and estrogen receptor binding are sufficient to trigger seasonal song nucleus growth. These data also suggest that T's effects on seasonal song nucleus growth may depend, in part, upon enzymatic conversion of T to bioactive metabolites.

Facultative development of courtship and communication in juvenile male cowbirds (Molothrus ater)

We investigated effects of naturally occurring variation in experience with adult males on development of song and courtship competence in captive juvenile cowbirds. We studied birds in groups housed in large outdoor aviaries that allowed birds to regulate access to social stimulation. In two aviaries, we housed juvenile males and females either with or without adult males. Birds remained in these conditions from September 1999 through their breeding season. We documented social and vocal development of juvenile males in the two aviaries by measuring social assortment and patterns and frequencies of their song interactions. We then brought the juveniles from the two aviaries together to compete against each other for access to females. In addition, we recorded juveniles' songs four times over the study and played back their breeding season songs to females in sound-attenuating chambers to measure the effectiveness of songs in eliciting copulatory responses from the females. Compared to juvenile males housed with adult males, juvenile males housed without adult males developed atypical behavior patterns. They (1) displayed little intrasexual aggression or near-neighbor associations and (2) exhibited different patterns of courtship and copulation, but (3) were as successful at competing for copulations. Furthermore, they developed stereotyped songs sooner and developed more potent breeding season songs. These different outcomes could not be traced to one variable but to a cascade of effects involving diverging patterns of song acquisition and social interaction. The patterns of social skills that emerged indicate considerable plasticity in the mechanisms underlying acquisition of courtship competence. Copyright 2002.