How Hormone-Sensitive Are Bird Songs And What Are The Underlying Mechanisms?
It is generally assumed that the main function of bird song is sexual, i.e. concerns mate attraction and territorial defense. In relation, singing is frequently thought to be a male behavior that is controlled by the gonadal production of testosterone and its androgenic and estrogenic neural metabolites. These hormones seem to act on the preoptic brain area to facilitate song performance and on the song control system to control song structure. However, in many species of the temperate zones males sing out-side of the breeding season when testosterone production is very low, in males of many tropical species singing occurs year-round including non-breeding periods, in a considerable number of species of the temperate zones females sing regularly in various periods of the year, in many tropical species females sing regularly solo or in male-female duets. Thus, the gonadal endocrine control of song performance and song structure is likely only for a sub-group of songbird species. The observation that female singing occurs scattered in most oscine families coincides with the observation that the song control system differentiates in males and females of all studied oscine species, but becomes rudimentary in species with non-singing females such as the zebra finch. Singing males and females, independently of their gonadal status and levels of blood testosterone, express high levels of androgen receptors in most areas of the neural song control system and estrogen receptors in the song area HVC, either throughout or in its caudo-medial extension (called para-HVC). Thus although circulating levels of testosterone and estradiol are low in non-breeding males and in non-breeding and breeding females, these low levels might still be functional or might be amplified in song areas. The mechanisms that explain any particular song structure are unknown but estrogenic activity in the HVC seems required for the production of song features typical of reproductively active males. This estrogenic activity seems to involve the regulation of BDNF (brain derived neurotrophic factor) in the HVC that then might act locally and trans-synaptically in song areas downstream of HVC.
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Document Type: Research Article
Publication date: July 1, 2014
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- Acta Acustica united with Acustica, published together with the European Acoustics Association (EAA), is an international, peer-reviewed journal on acoustics. It publishes original articles on all subjects in the field of acoustics, such as general linear acoustics, nonlinear acoustics, macrosonics, flow acoustics, atmospheric sound, underwater sound, ultrasonics, physical acoustics, structural acoustics, noise control, active control, environmental noise, building acoustics, room acoustics, acoustic materials, acoustic signal processing, computational and numerical acoustics, hearing, audiology and psychoacoustics, speech, musical acoustics, electroacoustics, auditory quality of systems. It reports on original scientific research in acoustics and on engineering applications. The journal considers scientific papers, technical and applied papers, book reviews, short communications, doctoral thesis abstracts, etc. In irregular intervals also special issues and review articles are published.
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