61,556 research outputs found
Song post exposure, song features, and predation risk
No full textMale birds use song to attract mates and deter other males, but in doing so, they also attract the attention of predators and parasites. Such viability costs are inherent in reliable signals, potentially causing females to prefer mates that display from the most exposed sites. However, viability costs of sexual signals may be ameliorated by affecting the choice of microhabitat, which in turn may affect the design of song features that are most efficiently transmitted in this microhabitat. We estimated the exposure of song posts (microsites used by males when singing) used by passerine birds in relation to prey selection by the sparrowhawk Accipiter nisus, by calculating the proportion of males that sang from song posts that were at the maximum level of the vegetation, in an attempt to quantify the costs of sexual selection. We quantified prey susceptibility to predation as the difference between the log-transformed observed number of prey minus the log-transformed expected number of prey in the environment. This prey susceptibility index increased with increasing song post exposure similarly in sexually dichromatic and monochromatic species, although the prey susceptibility index was related to sexual dichromatism. Song post exposure was dependent on habitat, but comparative models controlling for the potentially confounding effects of habitat, sexual dichromatism, hole nesting, coloniality, body mass, cognitive capacities, and flying abilities indicated that the relationship between the prey susceptibility index and song post exposure is strong. Path analyses of the relationship between song post exposure, sexual dichromatism, and prey susceptibility index revealed that selection acting on sexual dichromatism and song post exposure has secondary impact on prey susceptibility index. The opposite causal mechanisms by which predation affects sexual traits are less likely. These models suggest that female preference for high song posts or dichromatic plumage increases predation risk on an evolutionary time scale. Copyright 2006.birds; costs of sexual selection; prey selection; sound transmission
Extrapair paternity and the evolution of bird song
No full textBird song is usually considered to have evolved in the context of sexual selection. Because extrapair paternity is a major component of sexual selection, mating advantages at the social level for males that produce songs of high quality may be transformed into higher success in extrapair paternity. Therefore, males with longer and more complex songs should suffer less from extrapair paternity intraspecifically, whereas species with high rates of extrapair paternity, reflecting intense sperm competition, should produce more elaborate songs. Although some intraspecific studies demonstrated a negative link between features of songs and extrapair paternity in own nest, others failed to detect such a relationship. Contrary to expectation, a meta-analysis of all studies revealed no significant intraspecific evidence for songs being associated with extrapair paternity. In addition, in comparative analyses based on generalized least squares (GLS) models, we found that no measures of song complexity and temporal output were significantly related to extrapair paternity interspecifically, even when potentially confounding factors such as social mating system, life history, migration, habitat, or sexual dichromatism were held constant. Only plumage dichromatism was significantly related to extrapair paternity. The absence of both intra- and interspecific relationships between measures of song variability and extrapair paternity suggests that factors other than postmating sexual selection have been the important evolutionary forces shaping differences in song. Copyright 2004.bird song; evolution; extrapair paternity; generalized least squares; meta-analysis; repertoire size; sexual selection
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Expression of GABAA receptor subunit genes in the avian song system and their role in learning and memory
No full textγ-aminobutyric acid type A (GABAA) receptors are the primary mediators of inhibitory neurotransmission in the brain. In avian systems, 14 GABAA receptor subunits (α1-6; β2-β4; γ1, 2 and 4, δ and π) have been identified. These assemble into pentameric transmembrane structures with an intrinsic chloride-selective pore and are involved in the modulation of learning and memory. Following imprinting training in the one-day old chicken, mRNA encoding the GABAA receptor γ4 subunit is significantly reduced in learning-relevant brain regions indicating a role for receptors comprising this subunit in learning and memory. The zebra finch (Taenopygia guttata) song system has long since been used as a paradigm for studying the underlying molecular mechanisms of learning and memory due to the discrete nature of song, the song system and established stages in song development. The avian brain displays many comparable structures and pathways to mammalian systems and there are striking parallels between birdsong and speech production in humans hence the fundamental neuronal mechanisms are similar. Despite major developments towards understanding the anatomical and electrophysiological properties of various song-system nuclei, the nature of the underlying molecular and biochemical/genetic architecture remains largely unknown. Electrophysiological and pharmacological techniques have localised GABAA receptors in the song system and more recently the spatial distribution of γ4-subunit mRNA has been mapped, producing striking results
Unofficial culture of 1950–70-es: types and art abilities of role author song genre
No full textВ статье рассматривается авторская песня как форма оппозиции официальной идеологии. Отмечается установка на устное исполнение, общение с близким кругом людей. Анализируются аспекты содержания и разновидности ролевого героя, жанровая палитра.The article considers the author song as a form of opposition to the official ideology. The focus on a verbal performance and communication with a close circle of people are marked here. The aspects of meaning, varieties of role character and variety of genres are analyzed
Immune challenge mediates vocal communication in a passerine bird: an experiment
No full textSecondary sexual characters may have evolved in part to signal resistance to parasites. Avian song has been hypothesized to be involved in this process, but the role of parasites in modulating acoustic communication systems in birds remains largely unknown, owing to lack of experiments. We studied the relationship between parasitism, testosterone, song performance, and mating success in male collared flycatchers (Ficedula albicollis) by experimentally challenging their immune system with a novel antigen. We predicted that a challenge of the immune system would reduce song performance, and that this reduction would be conditional on the size of a visual sexual signal, the forehead patch that was previously found to reflect resistance. An antagonistic linkage between testosterone and immune function would predict that a challenge of the immune system should suppress testosterone level. An immunological treatment by sheep red blood cells (SRBCs) triggered a decrease in body mass, testosterone level, and song rate, but other song traits were not significantly affected by the antigen challenge. Initial testosterone level was associated with forehead patch size and all song traits except song rate. SRBC injection caused stronger reduction in song rate among males with smaller forehead patches, and the change in song rate was also predictable by song features such as strophe complexity and length. We show that song rate and other song characteristics may be important cues in male-male competition and female choice. These results suggest that parasite-mediated sexual selection has contributed in shaping a complex acoustic communication system in the collared flycatcher, and that testosterone may play an important role in this process. Parasitism may drive a multiple signaling mechanism involving acoustic and visual traits with different signal function. Copyright 2004.bird song; collared flycatcher; immunocompetence; parasites; secondary sexual characters; testosterone
Unofficial culture of 1950–70-es: types and art abilities of role author song genre
No full textВ статье рассматривается авторская песня как форма оппозиции официальной идеологии. Отмечается установка на устное исполнение, общение с близким кругом людей. Анализируются аспекты содержания и разновидности ролевого героя, жанровая палитра.The article considers the author song as a form of opposition to the official ideology. The focus on a verbal performance and communication with a close circle of people are marked here. The aspects of meaning, varieties of role character and variety of genres are analyzed
Heterologous Expression of a Putative Na+/H+ Antiporter in E. coli System Enhances Tolerance to pH Shock and Salt Stress
No full textDroplet de-entrainment by inertial impaction on vertical rods in an air-droplet mixture flow
No full textWe experimentally investigate the de-entrainment of droplets by inertial impaction on an array of vertical rods in an air-droplet mixture flow. The de-entrainment efficiencies are measured for a single rod, for a single row of rods, and for a multi-row of rods. We investigate the effects of the droplet mass flux (0.5-5.4kg/m(2) s), the droplet Weber number (3000-8000), the air velocity (0-6 m/s), the rod geometry, and the surface roughness on the de-entrainment, and the rod diameter-to-pitch ratio effect on the de-entrainment. The results for a single rod show that the de-entrainment efficiency decreases slightly as the droplet mass flux increases; however, in our experimental ranges, there is negligible dependence on the droplet Weber number, the air velocity, and the surface roughness. The rod geometry affects the de-entrainment efficiency. The results for a single row of rods show that the existence of neighboring rods promotes de-entrainment due to droplet splashing, and we develop a correlation to show the effect of diameter-to-pitch ratio on the de-entrainment. Using information on the de-entrainment efficiencies of a single rod and those of a single row of rods, we propose a correlation that predicts the de-entrainment efficiency for a multirow of rods with a staggered array. The RMS errors of the correlation from the de-entrainment efficiencies experimentally obtained are within 13.5%. (c) 2005 Elsevier B.V. All rights reserved
Traumatic identity and aura in David Lodge's "Author, author"
No full textEste artículo analiza la novela Author, Author (2004) de David Lodge como ejemplo de bioficción neo-victoriana centrada en una celebridad, en este caso concreto, Henry James. El género forma parte del renacimiento Victoriano actual que afecta a los estudios culturales en su conjunto. Mi argumento central es que la novela de Lodge constituye una respuesta a las ansiedades culturales actuales, en particular a las que se refieren a la crisis identitaria y autoría literaria, así como a la pérdida del aura artística de Walter Benjamin, sublimándolas a través de los traumas de finales del siglo XIX. La elección de James, como demuestra el artículo, no es casual. Es el último representante de un mundo perdido en el que el aura aún tenía un espacio; el ser humano en crisis y traumatizado porque no encaja en un status quo nuevo.This paper delves into David Lodge’s Author, Author (2004) as an example of neo-Victorian celebrity biofiction, more concretely on Henry James. The genre belongs to the wave of Victorian revival in current literature which also affects cultural studies in general. My main contention is that Lodge’s novel responds to current cultural anxieties, particularly the crisis of identity and authorship and the end of Walter Benjamin’s concept of aura, by sublimating them into late-nineteenth-century traumata. The choice of James is, the article argues, not casual. He represents the redeeming figure of a lost auratic world; the human in crisis, traumatized because he does not fit in the new status quo
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