1,720,976 research outputs found
Male Golden-collared Manakins Manacus vitellinus do not adapt their courtship display to spatial alteration of their court
No full textMale Golden-collared Manakins Manacus vitellinus perform an elaborate courtship display composed of acrobatic jumps between saplings delimiting a court on the forest floor. Males rehearse their displays for hours until they are executed with amazing precision and speed. Here we investigated the plasticity of the display by examining whether males modify their choreography in response to a disturbance, such as when a small branch is placed against one of the saplings. Male Manakins performed displays that were longer and lacked a key element that invites females to copulate, supporting the hypothesis that males learn a specific sequence of moves to build their choreography. © 2011 The Authors. Ibis © 2011 British Ornithologists' Union
Female choice for male motor skills
No full textSexual selection was proposed by Darwin to explain the evolution of male sexual traits such as ornaments and elaborate courtship displays. Empirical and theoretical studies have traditionally focused on ornaments; the reasons for the evolution of elaborate, acrobatic courtship displays remain unclear. We addressed the hypothesis that females choose males on the basis of subtle differences in display performance, indicating motor skills that facilitate survival. Male golden-collared manakins (Manacus vitellinus) perform elaborate, acrobatic courtship displays. We used high-speed cameras to record the displays of wild males and analysed them in relation to male reproductive success. Females preferred males that performed specific display moves at greater speed, with differences of tens of milliseconds strongly impacting female preference. In additional males, we recorded telemetrically the heart rate during courtship using miniature transmitters and found that courtship is associated with profoundly elevated heart rates, revealing a large metabolic investment. Our study provides evidence that females choose their mates on the basis of subtle differences in motor performance during courtship. We propose that elaborate, acrobatic courtship dances evolve because they reflect motor skills and cardiovascular function of males
Sexually dimorphic neural phenotypes in golden-collared manakins (manacus vitellinus)
No full textMale golden-collared manakins (Manacus vitellinus) perform a high-speed acrobatic courtship display punctuated by loud 'snaps' produced by the wings. Females join males on display courts to select individuals for copulation; females follow displaying males but do not perform acrobatics or make wing snaps. Sexually dimorphic courtship displays such as those performed by manakins are the result of intense sexual selection and suggest that differences between sexes exist at neural levels as well. We examined sex differences in the volume of brain areas that might be involved in the male manakin courtship display and in the female assessment of this display. We found that males had a larger hippocampus (HP, spatial learning) and arcopallium (AP, motor and limbic areas) than females when adjusted for the size of the telencephalon (TELE) minus the target area. Females had a larger ventrolateral mesopallium (MVL) both when adjusting for the size of the remaining TELE and by direct comparison. The entopallium (E) was not sexually dimorphic. The E is part of the avian tectofugal pathway and the MVL is linked to this pathway by reciprocal connections. The MVL likely modulates visually guided behavior via descending brainstem pathways. We found no sex differences in the volume of the cerebellum or cerebellar nuclei. We speculate that the HP is important to males for cross-season site fidelity and for local spatial memory, the AP for sexually driven motor patterns that are complex in males, and that the MVL facilitates female visual processing in selecting male display traits. These results are consistent with the idea that sexual selection has acted to select sex-specific behaviors in manakins that have neural correlates in the brain. © 2011 S. Karger AG, Basel
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Energetics of the acrobatic courtship in male golden-collared manakins (Manacus vitellinus)
No full textIn lek mating systems, females choose mates through indicators of quality, which males may exhibit by their performance of courtship displays. In temperate regions, displaying seasons are brief (one to two months), whereas in the tropics courtship seasons may be prolonged. Moreover, in temperate-breeding animals lekking behaviour can be energetically demanding, but little is known about the energy costs of lekking in tropical animals. Daily, over the course of a nearly seven-month-long breeding season, male golden-collared manakins (Manacus vitellinus) of Panamanian rainforests perform acrobatic courtship displays that markedly elevate heart rates, suggesting that they require high energy investment. Typically, animals of tropical lowland forests (such as manakins) exhibit a 'slow pace of life' metabolic strategy. We investigated whether male manakin courtship is indeed metabolically costly or whether the birds retain a low daily energy expenditure (DEE), as seen in other tropical species. To assess these questions, we calibrated manakin heart rate against metabolic rate, examined daily lek activity and, using telemetry, obtained heart rates of individual wild, lekking male manakins. Although metabolic rates peak during courtship displays, we found that males actually invest minimal time (only approx. 5 min d-1) performing displays. As a consequence, the DEE of approximately 39 kJ d-1 for male manakins is comparable to other lowland tropical species. The short, intense bursts of courtship by these birds make up only approximately 1.2% of their total DEE. Presumably, this cost is negligible, enabling them to perform daily at their arenas for months on end.publishe
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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