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1.  Song environment affects singing effort and vasotocin immunoreactivity in the forebrain of male Lincoln’s sparrows 
Hormones and behavior  2010;58(3):544-553.
Male songbirds often establish territories and attract mates by singing, and some song features can reflect the singer’s condition or quality. The quality of the song environment can change, so male songbirds should benefit from assessing the competitiveness of the song environment and appropriately adjusting their own singing behavior and the neural substrates by which song is controlled. In a wide range of taxa social modulation of behavior is partly mediated by the arginine vasopressin or vasotocin (AVP/AVT) systems. To examine the modulation of singing behavior in response to the quality of the song environment we compared the song output of laboratory-housed male Lincoln’s sparrows (Melospiza lincolnii) exposed to one week of chronic playback of songs categorized as either high or low quality, based on song length, complexity and trill performance. To explore the neural basis of any facultative shifts in behavior, we also quantified the subjects’ AVT immunoreactivity (AVT-IR) in three forebrain regions that regulate socio-sexual behavior: the medial bed nucleus of the stria terminalis (BSTm), the lateral septum (LS) and the preoptic area. We found that high quality songs increased singing effort and reduced AVT-IR in the BSTm and LS, relative to low quality songs. The effect of the quality of the song environment on both singing effort and forebrain AVT-IR raises the hypothesis that AVT within these brain regions plays a role in the modulation of behavior in response to competition that individual males may assess from the prevailing song environment.
PMCID: PMC2916047  PMID: 20399213
arginine vasotocin (AVT); bird song; competition; sexual selection; social behavior network
2.  Potential trade-off between vocal ornamentation and spatial ability in a songbird 
Biology Letters  2013;9(4):20130344.
Bird song is hypothesized to be a reliable indicator of cognition because it depends on brain structure and function. Song features have been found to correlate positively with measures of cognition, but the relationship between song and cognition is complicated because not all cognitive abilities are themselves positively correlated. If cognition is not a unitary trait, developmental constraints on brain growth could generate trade-offs between some aspects of cognition and song. To further clarify the relationship between song and cognition in song sparrows (Melospiza melodia), we examined repertoire size and performance on a spatial task. We found an inverse relationship between repertoire size and speed of spatial learning and suggest that a developmental trade-off between the hippocampus and song control nuclei could be responsible for this relationship. By attending to male song, females may learn about a suite of cognitive abilities; this study suggests that females may glean information about a male's cognitive weaknesses as well as his strengths.
PMCID: PMC3730647  PMID: 23697642
song; spatial learning; trade-off
3.  Song Competition Affects Monoamine Levels in Sensory and Motor Forebrain Regions of Male Lincoln's Sparrows (Melospiza lincolnii) 
PLoS ONE  2013;8(3):e59857.
Male animals often change their behavior in response to the level of competition for mates. Male Lincoln's sparrows (Melospiza lincolnii) modulate their competitive singing over the period of a week as a function of the level of challenge associated with competitors' songs. Differences in song challenge and associated shifts in competitive state should be accompanied by neural changes, potentially in regions that regulate perception and song production. The monoamines mediate neural plasticity in response to environmental cues to achieve shifts in behavioral state. Therefore, using high pressure liquid chromatography with electrochemical detection, we compared levels of monoamines and their metabolites from male Lincoln's sparrows exposed to songs categorized as more or less challenging. We compared levels of norepinephrine and its principal metabolite in two perceptual regions of the auditory telencephalon, the caudomedial nidopallium and the caudomedial mesopallium (CMM), because this chemical is implicated in modulating auditory sensitivity to song. We also measured the levels of dopamine and its principal metabolite in two song control nuclei, area X and the robust nucleus of the arcopallium (RA), because dopamine is implicated in regulating song output. We measured the levels of serotonin and its principal metabolite in all four brain regions because this monoamine is implicated in perception and behavioral output and is found throughout the avian forebrain. After controlling for recent singing, we found that males exposed to more challenging song had higher levels of norepinephrine metabolite in the CMM and lower levels of serotonin in the RA. Collectively, these findings are consistent with norepinephrine in perceptual brain regions and serotonin in song control regions contributing to neuroplasticity that underlies socially-induced changes in behavioral state.
PMCID: PMC3608548  PMID: 23555809
4.  Female Lincoln's sparrows modulate their behavior in response to variation in male song quality 
Behavioral Ecology  2010;21(3):562-569.
Sexually reproducing organisms should mate with the highest quality individuals that they can. When female songbirds choose a mate, they are thought to use several aspects of male song that reflect his quality. Under resource-limited environmental conditions, male Lincoln's sparrows (Melospiza lincolnii) vary among one another in several aspects of song quality, including song length, song complexity, and trill performance. In a 2-pronged approach, we tested whether variation in song quality of male Lincoln's sparrows influences the behavior of females that are in a reproductive-like state. Over two trials, we exposed females to songs from the high and low ends of the distribution of naturally occurring song quality variation and found a higher level of behavioral activity in females exposed to high-quality songs, especially when they had first been exposed to low-quality songs. We also examined female phonotaxis toward antiphonally played songs with experimentally elevated and reduced trill performance and found that females moved preferentially toward the songs with elevated trill performance. Contrary to most studies investigating the behavioral responses of wild, female songbirds to variation in male song, we obtained our results without administering exogenous estradiol, which can artificially perturb the female's physiology. Our results demonstrate that the behavior of female Lincoln's sparrows is modulated by the quality of male songs to which they are exposed and that trill performance plays a significant role in this behavioral modulation. Furthermore, as the order of song quality presentation matters, it appears that recent song experience also influences female behavior.
PMCID: PMC2854529  PMID: 22476505
bird song; mate choice; Melospiza lincolnii; phonotaxis; sexual selection; song playback; trill performance; vocal performance
5.  Economy of mate attraction in the Cassin's finch 
Biology Letters  2005;1(1):34-37.
Mate attraction can be costly. Thus, individuals should modulate it according to its probable benefits. Specifically, individuals should modulate mate-attraction efforts based on their need for, the probability of attracting, and the reproductive competence of prospective mates. We tested these predictions by monitoring song output in laboratory-housed male Cassin's finches (Carpodacus cassinii) before, during and after brief female exposure following variable periods of isolation from females. We inferred individual reproductive competence from the product of season and reproductive schedule, the latter estimated from moult progress. Males produced little song in the presence of a female but robustly elevated song output in response to female loss. However, mere absence of a female did not elevate song output in males unaccustomed to female proximity. Furthermore, song output in response to female loss increased with her reproductive competence. We suggest that individuals modulate mate-attraction effort based on the benefits such efforts are likely to yield.
PMCID: PMC1629057  PMID: 17148122
bird song; courtship; reproductive decisions; moult; reproductive schedule; seasonal breeding

Results 1-5 (5)