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PubMed1987

Retinohypothalamic projection and suprachiasmatic nucleus of the house sparrow, Passer domesticus.

The distribution of retinohypothalamic projections and the organization of the suprachiasmatic region of the hypothalamus was investigated in the house sparrow (Passer domesticus). Retinohypothalamic projections (RHT) were studied by two anterograde tracing methods, and hypothalamic organization was investigated immunohistochemically with antisera against a number of substances known to be present in the mammalian suprachiasmatic nucleus (SCN): bombesin (BBS), glutamic acid decarboxylase (GAD), 5-hydroxytryptamine (5HT), neuropeptide Y (NPY), neurotensin (NT), somatostatin (SS), substance P (SP), vasoactive intestinal polypeptide (VIP), and arginine vasopressin (AVP). Observations from these experiments were analysed within the framework of a cytoarchitectural study using Nissl-stained material. From this study, we have identified an area in the anterior hypothalamus which we believe is an avian homologue of the mammalian SCN. This area contains a nucleus located in close apposition to the optic chiasm between the dorsal supraoptic decussation (DSD) and the ventral lateral geniculate body (GLv) for much of its rostrocaudal extent. The central portion of this nucleus contains neurons that exhibit GAD- and BBS-like immunoreactivity and is the terminal field for the RHT. For this reason, we term this nucleus the visual SCN. It also contains axon plexuses exhibiting 5HT-like, SP-like, and NPY-like immunoreactivity and is bordered ventrally by AVP-like, SP-like, and NT-like immunoreactive cells and medially by VIP-like and SS-like immunoreactive cells. Although it is not established that these cell groups together compose a single suprachiasmatic nucleus, the organization in the avian brain of a nuclear complex with a retinorecipient area surrounded by nonvisual components would be very similar to that of the mammalian SCN.

Animals↗
PubMed1987

Response of sparrows to songs of deaf and isolation-reared males: further evidence for innate auditory templates.

Adult song sparrows (Melospiza melodia) were tested for response to songs of conspecific males that had been reared in acoustic isolation or deafened early in life. Territorial males responded more aggressively to playback of songs of isolated males than to songs of deafened males but did not discriminate between songs of deafened males and heterospecific songs. Captive females showed an identical pattern when their response was measured in terms of the number and intensity of courtship displays evoked by song. The results support the auditory template theory of song development in demonstrating that species-identifying features are present in songs of isolates and in showing that males unable to hear their own song production do not incorporate these species-identifying features into their songs.

Animals↗
PubMed2003

Fos-like immunoreactivity in catecholaminergic brain nuclei after territorial behavior in free-living song sparrows.

The catecholaminergic cell groups of the brainstem play an important role in the regulation of motivated behavior, including reproductive behavior. In songbirds, these cell groups project to telencephalic nuclei involved in singing and contain steroid hormone receptors, implicating them in the seasonal regulation of song. Whether these nuclei are involved in the activation of song on a short-term, moment-to-moment basis is unknown. In this study, free-living male song sparrows (Melospiza melodia) were subjected to simulated territorial intrusion (STI), which stimulates territorial singing. The resulting fos-like immunoreactivity (FLI) was quantified in two HVc- and RA-projecting catecholaminergic regions of the brainstem: the area ventralis of Tsai (AVT) and the midbrain central gray (GCt). Males subjected to STI showed more FLI in both of these regions than control males. In addition, FLI in both nuclei was correlated positively with the number of songs sung in response to STI. The number of flights directed at the intruder was correlated with FLI in AVT but not GCt. These results suggest a role for AVT and GCt, and thus possibly catecholamines, in the regulation of territorial behavior in songbirds.

Agonistic Behavior↗
PubMed1987

Correlations between song acquisition, song production, and plasma levels of testosterone and estradiol in sparrows.

Male birdsong is a sexually dimorphic behavior characterized by learned dialects. In a combined study of learning in relation to steroid levels in the plasma, changes in estradiol and testosterone levels were correlated with the timing of the sensitive period for song acquisition and with successive stages in song development. Male swamp sparrows were trained with a changing series of live singing tutors from 26 days to 1 year of age. Song acquisition was concentrated between 26 and 47 days of age (57%). By 85 days of age 71% of acquisition was completed; some occurred as late as 300 days. There were two major periods when testosterone levels were elevated. The first, from 30-80 days, encompassed most of the period of song acquisition. The second, from 260 to at least 360 days of age, coincided with song development. Estradiol levels were elevated from 18 to 170 days of age, encompassing almost all of the period of song acquisition. A marked estradiol peak between 40 and 50 days coincided with a trough in testosterone levels and a hiatus in song acquisition. The strong correlation between the second period of elevated testosterone and song motor development suggests a causal connection, with levels peaking in mid-development and declining during mature song production. Estradiol levels were elevated at the start of the study and remained so during early subsong production, from 30 to 165 days. They then fell to baseline, remaining there throughout the resumption of subsong and plastic song production at 250-326 days. Both estradiol and testosterone are candidates for possibly affecting song acquisition.

Aging↗
PubMed1995

White-throated sparrow morphs that differ in song production rate also differ in the anatomy of some song-related brain areas.

White-throated sparrows are unusual among songbirds in that they occur in two color morphs, white-striped and tan-striped, determined by a chromosomal inversion and maintained by negative assortative mating. These differ in several reproductive behaviors, including amount of singing: white-striped males sing frequently, tan-striped females never sing, and tan-striped males and white-striped females sing an intermediate amount. The present study measures the volumes of several nuclei in the avian song system and relates these to color morph and to sex. We find that robustus archistristalis and the tracheosyringeal part of the hypoglossal nucleus, nuclei closely involved in song production, are larger in white-striped than in tan-striped birds. We also find morph differences for nuclei in the rostral division of the song system, nuclei believed to be less directly involved in song production. We find sex differences throughout the song system as has been reported in other songbirds. Relationships between structure and function in the song system are discussed.

Animals↗
PubMed1998

Song learning and vocal tradition in Nuttall's white-crowned sparrows.

We investigated song sharing and dispersion of song types in the wild in a colour-marked population of the non-migratory Nuttall's white-crowned sparrow, Zonotrichia leucophrys nuttalli. The songs of fathers, their male progeny (sons), and the neighbours of the sons at recruitment sites were analysed spectrographically and compared qualitatively and quantitatively. To determine whether a son's song more closely matched that of his father or a neighbour at the site settled, we subjected frequency and temporal characteristics of songs within each father-son-neighbour triad to multivariate cluster analysis. The songs of 14 of 16 sons clustered with their neighbours' rather than their fathers' songs, confirming that song matching of neighbours is an integral component of territory settlement by juveniles. Principal components analysis of frequency and temporal measurements of song within a dialectal area show that songs group into neighbourhoods and are non-randomly distributed. Multivariate analysis suggests that sons may entrain on frequency and temporal characteristics of a neighbour's song without matching phrases or complex syllables. Implications for models of instructive versus selective learning are discussed. The timing of closure of the sensitive phase, the length of the silent interval between the sensory phase and plastic song stage, and the time to song crystallization remain open questions in song ontogeny. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1998

Cultural variation in savannah sparrow, Passerculus sandwichensis, songs: an analysis using the meme concept.

I used the meme concept to investigate patterns of cultural variation among the songs of eight, geographically distinct populations of savannah sparrows. Memes composed of only one syllable were geographically widespread and randomly distributed among populations, but memes of two-, three- and four-syllables became progressively more restricted in their geographical distribution. Thus, the populations were memetically more similar with respect to one-syllable memes and more divergent with respect to larger memes. These results suggest that differences in memetic mutation rates and susceptibility to loss by memetic drift could be sufficient to create the observed pattern of greater divergence among populations for large memes. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1999

Mate, neighbour and stranger songs: a female song sparrow perspective.

We investigated discrimination by female song sparrows Melospiza melodia, between different categories of male song using the copulation solicitation display as a preference assay. Females responded most strongly to songs recorded from their mates, less strongly to songs of neighbouring males and least strongly to songs of stranger males. Among the stranger songs, however, females preferred songs that were most similar structurally to song types in their mates' repertoires (matching songs). These results are interpreted as evidence that females can recognize individual males based on the songs in their repertoires. Moreover, the observed female preferences for nonmatching neighbour and matching stranger song over nonmatching stranger song, suggest that any male with songs structurally similar to mate songs or even to nonmate but local neighbourhood songs, will be at an advantage in sexual interactions with local females. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2000

Song-type matching between neighbouring song sparrows.

In our study population, neighbouring song sparrows typically share two or more of their 6-10 song types. In an earlier experiment, we found that established neighbours typically reply to playback of neighbour-shared song with a different song they share with that neighbour ('repertoire matching'), rather than with the same song ('type matching') or with a nonshared song. In the present experiment, we considered the hypothesis that type matching is a threat or warning signal (Krebs et al. 1981, Animal Behaviour, 29, 918-923). We tested the specific prediction that a bird is more likely to type-match early in the breeding season when territory boundaries are new and still unstable, and more likely to repertoire-match later in the season, once those boundaries have become well established. Birds were played a shared song of a new neighbour once early (April) and again late (June) in the breeding season. As predicted, early in the season birds usually type-matched the playback (73% of the trials) but late in the season they type-matched only rarely (18%); birds never replied (early or late) with a nonshared song type. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2000

Social influences during song development in the song sparrow: a laboratory experiment simulating field conditions.

Oscine songbirds are exposed to many more songs than they keep for their final song repertoire and little is known about how a bird selects the particular song(s) to sing as an adult. We simulated in the laboratory the key variables of the natural song learning environment and examined the song selection process in nine hand-reared male song sparrows, Melospiza melodia, a species in which males sing 5-11 song types. During their second and third months (their presumed sensitive period), subjects were rotated equally among four live adult male tutors that had been neighbours in the field. Tutors were housed in individual aviary 'territories' in four corners of the roof of a building; subjects could see only one tutor at a time, but they could hear the others at a short distance. Later in their first year (months 5-12), half the subjects were again rotated among all four tutors and the other half were randomly stationed next to just one tutor. Results from this experiment confirm and extend the findings from our two previous field studies of song learning in this species. Young males in this experiment (1) learned whole song types, (2) learned songs from multiple tutors, (3) preferentially learned songs that were shared among their tutors, (4) learned songs that other young males in their group also chose, and (5) learned more songs from the tutor they were stationed next to during the later stage (stationary subjects). These last two results support the late influence hypothesis that interactions after a bird's sensitive period affect song repertoire development. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2000

Re-expression of songs deleted during vocal development in white-crowned sparrows, Zonotrichia leucophrys.

White-crowned sparrows learn and produce multiple song types as juveniles, but most individuals stop singing all except one by the end of the first singing season. This single song type is generally maintained throughout adulthood. We demonstrate that, at the start of the second and subsequent singing seasons, this species can recall songs that had been deleted during the first singing season. The re-expression of song occurred in both the oriantha and the gambelii subspecies. Although all our males recrystallized the original song in the second year, our results indicate a mechanism for seasonal song change without new song memorization. The traditional dichotomy of closed-ended versus open-ended learning is inadequate for birds that learn early in life but can change their song output seasonally. We suggest that species can exhibit a closed sensitive period for song memorization and first production, with the ability to recall deleted songs later in life. This type of learning, selective attrition followed by subsequent re-expression, may be used by some species currently considered open-ended learners. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2000

Song overproduction, selective attrition and song dialects in the white-crowned sparrow.

Male Puget Sound white-crowned sparrows, Zonotrichia leucophrys pugetensis, form large vocal dialects along the Pacific northwest coast of North America. Most adult males sing a single song dialect throughout their lives. To determine how dialects are maintained in this species, I studied two populations at the Columbia River mouth in a contact zone between two dialects. Singers of each of the two dialects clustered together in space, forming local song 'neighbourhoods'. Two hypotheses for the maintenance of dialects were tested. The late acquisition hypothesis predicts that yearling or adult male immigrants memorize their song from the territory neighbours they settle next to. The selective attrition hypothesis predicts that males memorize a variety of dialects early in life, overproduce song dialects upon arrival, and later selectively retain the one prelearned dialect that best matches what their neighbours sing. In 1997 and 1998, 35-40% of new territory occupants sang two dialects upon arrival in April, and then over the course of days to several weeks, discarded one dialect from their repertoire. Fourteen of 16 (88%) kept as their adult song the dialect that matched the dialect sung by the majority of their neighbours. No male added a new dialect to his repertoire after arrival, nor did males alter their retained dialect to more closely resemble their neighbours' songs. New arrivals that overproduced dialects upon arrival were significantly more likely to match their neighbours' dialect than males that did not overproduce upon arrival. In a playback experiment, males in the overproduction stage engaged in matched countersinging to the dialect played to them. These observations and the experiment support the selective attrition hypothesis: males visit and memorize a variety of dialects, probably in their hatching-year summer, overproduce dialects upon arrival the next spring, and then selectively retain the one dialect that matches the local song culture. Vocal plasticity late in life is not the result of a late sensitive phase for song memorization, but rather results from behavioural selection operating on a pre-existing repertoire of song dialects. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1996

Interrelationship of day length and temperature on the control of gonadal development, body mass, and fat score in white-crowned sparrows, Zonotrichia leucophrys gambelii.

We tested the effects of naturally relevant environmental temperatures on long day-induced reproductive development in male and female white-crowned sparrows, Zonotrichia leucophrys gambelii. Transfer from short days (8L 16D) to long days (20L 4D) resulted in rapid testicular development and partial ovarian development as has been reported many times previously. Exposure of experimental groups to low (5 degrees), moderate (20 degrees), and high (30 degrees) temperature during photostimulation had only subtle effects on plasma levels of follicle-stimulating hormone and luteinizing hormone over time and no effects on the size of testes, cloacal protuberance, ovaries, or brood patch at Day 30 of treatment. Long days resulted in the well known increase in body mass and fat score, indicative of preparations for migration. In females, treatment with low temperature resulted in a reduction in the premigratory increase in fat and body mass when transferred to long days. This was accompanied by an increase in plasma levels of corticosterone during the early stages of photostimulation at low temperature. Temperature regimes had no effects on fattening or body mass in males, despite an early increase in plasma corticosterone at low temperature. Circulating levels of thyroxine (T4) and triiodothyronine (T3) increased to varying degrees following photostimulation. Temperature treatment had no effect on plasma levels of thyroid hormones in males, but low temperature did inhibit thyroid hormone secretion (particularly T4) in females. Although reproductive development appears to be resistant to naturally relevant temperature extremes in both sexes, low environmental temperature impaired preparations for migration in females but not males. This effect may be mediated through glucocorticosteroids and not thyroid hormones. Reasons for the sexual dimorphism in this response are unknown, but may be related to sexual selection for males to arrive on the breeding grounds ahead of females regardless of local weather conditions.

Adipose Tissue↗
PubMed1997

Effects of day length and temperature on gonadal development, body mass, and fat depots in white-crowned sparrows, Zonotrichia leucophrys pugetensis.

We tested the effects of ambient temperature (5 degrees, 20 degrees, and 30 degrees) on photoperiodically induced reproductive functions in male and female white-crowned sparrows, Zonotrichia leucophrys pugetensis. Transfer from short days (9L 15D) to long days (16L 8D) resulted in rapid testicular growth and partial ovarian development in all three temperature treatments. There were no differences in sizes of testes and cloacal protuberance following 30 or 70 days of exposure to long days at the different temperatures. However, brood patch and follicular development were enhanced in females at 30 degrees compared with the 5 degrees and 20 degrees groups. Many of these females exposed to 30 degrees had large yolky follicles by Day 70. This enhancement was evident only when females were housed in the same room with males, however. Despite the effects of high temperature on ovarian development, there were no differences among groups in plasma levels of follicle-stimulating hormone or luteinizing hormone, suggesting that differential ovarian development may have been mediated by gonadal sensitivity to gonadotropins rather than by differential secretion of these hormones. We examined circulating levels of corticosterone (B) and both tri-iodothyronine (T3) and thyroxine (T4) as possible regulators of this differential ovarian sensitivity to gonadotropins. Plasma B levels showed transitory increases in males at 5 degrees and 20 degrees, but were suppressed in males at 30 degrees. Titers of B were not influenced by temperature treatments in females. Circulating T4 increased following photostimulation in both sexes, but this increase was reduced at 5 degrees. T3 concentrations in plasma were highly variable and not influenced by either photo-period or temperature in males, but were significantly lower in females exposed to 30 degrees by Day 70. Thus, B and T4 levels do not appear to help explain differential ovarian development, but circulating T3 levels cannot yet be excluded as a regulator of ovarian sensitivity to gonadotropins. Long days resulted in no change, or a gradual decrease, in body mass and fat deposit in males and females, and temperature regimes had no further effects on fattening or body mass. Thus, reproductive development under long days appears to be resistant to naturally relevant temperature extremes in male Z.l. pugetensis, whereas follicular development (i.e., yolk deposition in follicles leading to ovulation and onset of nesting) can be enhanced by high temperature. Reasons for the dimorphism in this response are unknown, but may be explained by the role of females in determining onset of final ovarian maturation and nesting in relation to favorable environmental conditions. In a second experiment, in which the sexes were isolated from one another, we determined the effects of the same treatments on.Z.I. pugetensis. Again there was no effect of temperature on photoperiodically induced testicular growth, and the enhancement of follicular development in females at 30 degrees was greatly reduced in the absence of males. We also continued this experiment up to 116 days of treatment to investigate effects on onset of photorefractoriness (spontaneous gonadal regression) and onset of prebasic moult. In both sexes it was clear that low temperature (5 degrees) retarded gonadal regression and high temperature (30 degrees) advanced it. Similarly, the prebasic moult score was greater at 30 degrees and less at 5 degrees in both sexes. There were no effects of temperature on plasma levels of LH at Day 116 of treatment, but plasma levels of T4 were higher in the 5 degrees group of both males and females sampled at Day 116. Clearly, the effects of temperature can have different effects on gonadal recrudescence, onset of breeding (yolk deposition), and termination of breeding. Whether these influences of temperature on reproductive function at different stages in the breeding cycle have different mechanisms remains to be determ

Adipose Tissue↗
PubMed1998

Thyroidectomy of house sparrows (Passer domesticus) prevents photo-induced testicular growth but not the increased hypothalamic gonadotrophin-releasing hormone.

Thyroidectomy of starlings (Sturnus vulgaris) prevents the decrease in hypothalamic gonadotrophin-releasing hormone (GnRH) which normally occurs at the onset of photorefractoriness. To extend this observation to another species, changes in testicular mass, bill colour, moult, and hypothalamic GnRH content were monitored in photostimulated and nonphotostimulated intact and thyroidectomized house sparrows (Passer domesticus). Photostimulated intact birds rapidly increased testicular mass and GnRH. Later, testicular mass and GnRH decreased, and birds moulted, as they became photorefractory. Nonphotostimulated intact birds showed an increase in testicular mass and GnRH. Neither photostimulated nor nonphotostimulated thyroidectomized birds showed a marked increase in testicular mass, but both showed an increase in GnRH. Photostimulated thyroidectomized birds showed no subsequent decrease in GnRH and they did not moult. It is suggested that in this species, thyroidectomy inhibits the release of GnRH as well as preventing the downregulation of GnRH synthesis normally associated with the development of photorefractoriness.

Animals↗
PubMed1999

Effects of ambient temperature on photo-induced prolactin secretion in three subspecies of white-crowned sparrow, Zonotrichia leucophrys.

We tested the effects of naturally relevant ambient temperatures (5, 20, and 30 degrees C) on photoinduced prolactin (PRL) secretion in three subspecies of white-crowned sparrow, Zonotrichia leucophrys. In all three subspecies, transfer from short to long days triggered an increase in plasma PRL typical of an avian seasonal breeder. In Z. l. gambelii, which breeds at high latitudes, temperature does not affect the rate of photoinduced gonadal maturation or luteinizing hormone (LH) secretion. In this subspecies, we found that changes in plasma PRL concentrations were similar in all temperature treatments. In Z. l. pugetensis, which breeds in the Pacific Northwest, high temperatures accelerate gonadal development in females but not males and does not affect LH secretion. In this subspecies, we found that like gonadal growth, photoinduced changes in PRL secretion in Z. l. pugetensis vary with ambient temperature in females but not males. In Z. l. oriantha, which breeds in alpine regions of the West, both males and females respond to temperature cues by modulating gonadal growth but not LH secretion. We found in Z. l. oriantha that ambient temperature affects PRL secretion in both sexes. These results suggest that PRL may be involved in the transduction of ambient temperature cues used to time reproductive development and the termination of seasonal breeding. Alternatively, temperature-mediated differences in plasma PRL may be a result rather than a cause of differences in gonadal development, since sex steroids affect PRL secretion in some species.

Animals↗
PubMed2001

Seasonal growth of song control nuclei precedes seasonal reproductive development in wild adult song sparrows.

In seasonally breeding adult songbirds, the brain regions that control song undergo dramatic seasonal morphological changes. During late winter and early spring, increasing day length triggers an increase in circulating testosterone that ultimately causes several song nuclei to grow in volume. The timing of this growth relative to the seasonal development of the reproductive system is not known. This question was investigated in two populations of wild song sparrows (Melospiza melodia morphna). Both populations live at the same latitude (46 degrees N), but breed at different altitudes. One population resides on the Pacific coast in Washington, and the other resides in the foothills of the Cascade Mountains. Both populations experienced the same photoperiodic conditions, but the timing of seasonal reproductive development differed between populations. Coastal birds initiated gonadal recrudescence approximately 2 weeks earlier than montane birds. Despite this temporal difference in reproductive development, there were no differences between these groups in the seasonal growth of two song control nuclei, HVc and RA. During late February, both groups had low circulatory levels of testosterone (mean for coastal birds was 1.01 +/- 0.37 ng/ml; mean for montane birds was 1.41 +/- 0.26 ng/ml) and fully recrudesced song nuclei (for example, mean HVc volume in coastal birds was 1.77 +/- 0.08 mm(3); mean HVc volume in montane birds was 1.76 +/- 0.09). Also at this time, both populations were in the earliest stages of seasonal reproductive development as judged by the degree of gonadal recrudescence (mean gonad volume was less than 10% of typical breeding size in both populations). It is concluded that seasonal song system growth is completed before seasonal reproductive development in response to submaximal levels of circulating testosterone.

Animals↗
PubMed1994

Behavioral and hormonal responses of male song sparrows to estradiol-treated females during the non-breeding season.

Previous studies on several species have shown that behavior of female vertebrates given estradiol implants to maintain sexual receptivity resulted in elevated levels of testosterone in males and even delayed termination of breeding in their otherwise untreated mates. However, the efficacy of such treatment in the non-breeding season was unclear. In this study, female song sparrows, Melospiza melodia morphna, given implants of estradiol in autumn showed elevated sexual behavior--especially "chitters," a loud, female-specific vocalization used mostly during the breeding season. Males in autumn appeared to ignore the sexual behavior of these females, showed no difference in response to simulated territorial intrusion, and had basal circulating levels of testosterone when compared with males tested in an area of control females. However, by late winter (February) males in the area where females were treated with estradiol had elevated levels of testosterone compared to control males and those of both groups sampled in autumn. These data indicate that sexual behavior of females, experimentally induced by estradiol implants, failed to increase sexual and territorial behavior in males during the autumn. On the other hand, reproductive behavior of females did appear to accelerate the vernal increase in testosterone concentrations in blood of males.

Aggression↗