179,417 research outputs found
Entrevista de H. Rosi Song con Toni Massanés
No full textEntrevista de H. Rosi Song a Toni MassanésInterview by H. Rosi Song with Toni Massané
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
AN EFFECTIVE OVERLAY H.263+VIDEO MULTICAST SYSTEM OVER THE INTERNET
No full textThis paper presents an effective overlay H.263+ video multicast system over the Internet. The proposed system consists of overlay multicast tree construction, target bandwidth determining process, and H.263+ rate control. Overlay multicast tree construction algorithm and target bandwidth determining process work alternatively to satisfy the average delay constraint, and H.263+ rate control is implemented to enhance the human visual perceptual quality over the multicast tree. Finally, experimental results are provided to show the performance of the proposed system.X11sciescopu
Sexually size dimorphic brains and song complexity in passerine birds
No full textNeural correlates of bird song involve the volume of particular song nuclei in the brain that govern song development, production, and perception. Intra- and interspecific variation in the volume of these song nuclei are associated with overall brain size, suggesting that the integration of complex songs into the brain requires general neural augmentation. In a comparative study of passerine birds based on generalized least square models, we tested this hypothesis by exploring the interspecific relationship between overall brain size and repertoire size. We found no significant association between song complexity of males and brain size adjusted for body size. However, species in which males produced complex songs tended to have sex differences in overall brain size. This pattern became stronger when we controlled statistically for female song complexity by using sex differences in song complexity. In species with large differences in song complexity, females evolved smaller brains than did males. Our results suggest no role for the evolution of extended neural space, as reflected by total brain size, owing to song complexity. However, factors associated with sexual selection mirrored by sex differences in song complexity were related to sexual dimorphism in overall brain size
Song sharing and repertoire change as indicators of social structure in the Noisy Scrub-bird
No full textThe Endangered Noisy Scrub-bird is a small passerine that is seldom seen but often heard in its range on the south coast of Western Australia. The difficulties in observing this cryptic bird mean that little is known about its social system. The loud, conspicuous territorial song of the male provides a convenient, non-intrusive means by which to study this species.
The aim of this project was to investigate the patterns of song sharing and repertoire change in the Noisy Scrub-bird to provide indications of the social structure. It was found that groups of up to ten territorial males shared the same set of about five song types. Song groups were discrete, with members of a song group sharing most, if not all, of their song types. Males from different song groups had no song types in common.
Repertoire change was rapid and, with the exception of one individual, was found in every territorial male studied in the Mt Gardner population. It occurred simultaneously in all members of a song group, with males making the same changes to their shared songs. The source of repertoire change was mainly modification of existing song types with occasional divergence of a single song type into two distinct song types, as well as some innovation providing new song types. The average life of a song type was approximately 6 months. Although some song types persisted for the entire 16 month sampling period, they were continually modified and a year later could no longer be recognised as the same type.
Translocation of eight male scrub-birds to the Porongurup National Park provided an opportunity to combine individuals that initially did not share any songs. This allowed the process of song group formation to be studied. Within a one to two month period these males altered their songs so that they shared with their new neighbours. There was some evidence that the songs of dominant males were copied. Observation of the population established on Bald Island by translocation confirmed that there were no appreciable long-term effects on the songs of translocated Noisy Scrub-birds. Song group size, repertoire size and levels of song sharing were very similar to those found in the Mt Gardner population.
The striking feature of Noisy Scrub-bird song groupings was their discreteness and cohesiveness even in the presence of continual repertoire change. It is suggested that each song group consists of a dominant male whose songs are more attractive to females and/or effective in territory defence. This dominant male is surrounded by subordinate males that copy his effective songs. Repertoire change can be explained by the dominant male continually making changes to his songs, with the other males copying these changes to retain their mimicked effectiveness. Each song group may in fact represent a dispersed lek. The scenario suggested to explain Noisy Scrub-bird song groupings bears striking similarities to the hotshot hypothesis to explain lek formation whereby males cluster around a successful male.
This study demonstrates the potential of using song to investigate aspects of the social system of a species which is otherwise very difficult to observe. Management of an Endangered species such as the Noisy Scrub-bird will always benefit from increased knowledge about their social system. For example, this study showed that taking males from different song groups for translocation probably has little impact on their success at the new site because of their ability to rapidly alter their songs to form new song groups. An additional benefit of regularly monitoring the songs of translocated males was that it allowed ongoing identification of individuals, even though their songs were continually changing
Delayed development of song control nuclei in the zebra finch is related to behavioral development
No full textHerrmann K, Bischof H-J. Delayed development of song control nuclei in the zebra finch is related to behavioral development. The Journal of Comparative Neurology. 1986;245(2):167-175.The postnatal development of two visual areas (nucleus rotundus and ectostriatum) and two song control areas (hyperstriatum ventrale pars caudale, HVc, and nucleus robustus archistriatalis, RA) of the zebra finch brain was followed from birth to adulthood. The following parameters were investigated: (1) neuron size, (2) volume of the brain nuclei, and (3) myelination of axons. The nucleus rotundus, the diencephalic station of the tectofugal pathway, exhibits the fastest development: rotundal neurons reach their maximum size at 20 days of age; the volume of this structure reaches adult size at the same time. The process of myelination begins between day 5 and day 10 and is completed at 40 days of age. A similar temporal sequence of development is seen in the ectostriatum, except myelination starts some days later. Thus the development of these visual areas is completed at 40 days. In, contrast, the development of the song control nuclei is delayed. Neurons in RA and HVc grow steadily up to 40 days of age, attaining a size larger than that observed in adults. Whereas the volume of HVc increases until day 40 and remains stable thereafter, RA volume increases until day 70 and evidences a decrease thereafter. It is not until postnatal day 20 (RA) and day 40 (HVc) that the myelination process starts in the song control areas. Adult myelin density is achieved by 70 days in RA and by 100 days in HVc. It can be demonstrated that the development of the visual system parallels the development of visual performance of the birds. Delayed growth of song control nuclei coincides with development of song
Age-dependent health status and song characteristics in the barn swallow
No full textBird song has been hypothesized to evolve, partly, to signal health status of males, and song features should therefore correlate with parasite load. Immune function, parasitism, and secondary sexual characters can, however, differ between age classes, and any apparent relationship between song and parasite loads can be the result of systematic age effects. We tested for an age-dependent relationship between sexually selected characters and measures of parasitism in a Spanish population of the barn swallow Hirundo rustica. A comparison across age classes revealed that chewing lice load, song duration, mean peak amplitude frequency of songs, and tail length differed significantly between yearlings and adults. In a longitudinal analysis, we found significant evidence for mean peak amplitude frequency of songs, tail length and chewing louse parasitism, and a nonsignificant tendency for song duration to change with age of an individual. We found a significant association between song duration and chewing louse load and between hematocrit and peak amplitude frequency of the rattle, the typical harsh terminal syllable. In tests for associations between song traits and health status, while controlling for age, age and chewing louse load were independently related to song duration. We found a significant relationship between pairing success and song duration, implying that females may use this song trait in their choice of parasite-free males. Although the song of the barn swallow may provide information about both male age and parasite resistance, signaling of health status appears to be independent of age effects, in accordance with the theory of parasite-mediated sexual selection, suggesting that male signals can be used as reliable indicators of parasitism. Copyright 2005.age; barn swallow; bird song; chewing louse; hematocrit; sedimentation rate
Sexual selection on song and cuticular hydrocarbons in two distinct populations of Drosophila montana
No full textSexual selection has the potential to contribute to population divergence and speciation. Most studies of sexual selection in Drosophila have concentrated on a single signaling modality, usually either courtship song or cuticular hydrocarbons (CHCs), which can act as contact pheromones. We have examined the relationship between both signal types and reproductive success using F1–3 offspring of wild- collected flies, raised in the lab. We used two populations of the Holarctic species Drosophila montana that represent different phylogeographic clades that have been separate for ca. 0.5 million years (MY), and differ to some extent in both traits. Here, we characterize the nature and identify the targets of sexual selection on song, CHCs, and both traits combined within the populations. Three measures of courtship outcome were used as fitness proxies. They were the probability of mating, mating latency, and the production of rejection song by females, and showed patterns of association with different traits that included both linear and quadratic selection. Courtship song predicted courtship outcome better than CHCs and the signal modalities acted in an additive rather than synergistic manner. Selection was generally consistent in direction and strength between the two populations and favored males that sang more vigorously. Sexual selection differed in the extent, strength, and nature on some of the traits between populations. However, the differences in the directionality of selection detected were not a good predictor of population differences. In addition, a character previously shown to be important for species recognition, interpulse interval, was found to be under sexual selection. Our results highlight the complexity of understanding the relationship between within-population sexual selection and population differences. Sexual selection alone cannot predict differences between populations.Peer reviewe
Wireless link state-aware H.264 MGS coding-based mobile IPTV system over WiMAX network
No full textThis paper presents a simple but effective architecture for the transmission of H.264 MGS coding-based IPTV stream over WiMAX network. The proposed system is implemented to provide more subscribers with an enhanced mobile IPTV service considering their wireless link states. In the proposed system, the base layer of the IPTV stream is transmitted with the sparsest modulation scheme and the lowest coding rate to provide IPTV service of minimum quality to as many subscribers as possible. And some parts of the enhancement layer are transmitted with the modulation scheme and the coding rate adaptive to wireless link states of subscribers. Basically, we pursue an efficient tradeoff between the number of subscribers that receive the enhancement layer stream and their IPTV service quality. Finally, experimental results are provided to show the performance of the proposed system. (C) 2009 Elsevier Inc. All rights reserved.X116sciescopu
Humpback whale song on the southern ocean feeding grounds: implications for cultural transmission
No full textMale humpback whales produce a long, complex, and stereotyped song on low-latitude breeding grounds; they also sing while migrating to and from these locations, and occasionally in high-latitude summer feeding areas. All males in a population sing the current version of the constantly evolving display and, within an ocean basin, populations sing similar songs; however, this sharing can be complex. In the western and central South Pacific region there is repeated cultural transmission of song types from eastern Australia to other populations eastward. Song sharing is hypothesized to occur through several possible mechanisms. Here, we present the first example of feeding ground song from the Southern Ocean Antarctic Area V and compare it to song from the two closest breeding populations. The early 2010 song contained at least four distinct themes; these matched four themes from the eastern Australian 2009 song, and the same four themes from the New Caledonian 2010 song recorded later in the year. This provides evidence for at least one of the hypothesized mechanisms of song transmission between these two populations, singing while on shared summer feeding grounds. In addition, the feeding grounds may provide a point of acoustic contact to allow the rapid horizontal cultural transmission of song within the western and central South Pacific region and the wider Southern Ocean
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