1,721,071 research outputs found
The number and coloration of white flank spots predict the strength of a cutaneous immune response in female Diamond Firetails, Stagonopleura guttata
No full textColour variation in birds is often used to signal functional differences between individuals and sexes, though white plumage has usually been disregarded because white feathers were thought to be cheap to produce and hence unreliable signals. Here, we provide evidence for sex-specific morphological and colour differences in the strikingly patterned but apparently monomorphic Diamond Firetail (Stagonopleura guttata). We found that males had longer and darker tails, wider lores and a darker bill, while females had significantly more white flank spots. These gender-specific trait differences could be used to signal individual quality in sexual or social interactions, and hence we examined the correlation between these traits and the cell-mediated immune response (phytohaemagglutinin, PHA test). During both the breeding and non-breeding seasons, we found a positive correlation between PHA response and white flank spot number as well as their ultra-violet reflectance in females, and a negative correlation with white chroma and hue. In males, there was a positive correlation between PHA response and red rump reflectance (hue, red-chroma). There was no association between PHA response and either tail length or lore depth in either sex. These results add to a growing body of evidence that female spot number and white plumage reflectance signal quality
Males with a Faster Courtship Display have More White Spots and Higher Pairing Success in the Diamond Firetail,Stagonopleura guttata
No full textThere is growing evidence that female mate choice could be based on a combination of multiple signals that often involve both ornamental colourful traits and behavioural displays. The Diamond Firetail is an Australian finch with a variable number of white spots on their black flank feathers. The number of white spots is a dimorphic characteristic: females have more spots than males, and males prefer females with many spots. Previously, we found assortative pairing for spot number despite the absence of experimental evidence for female preference for male spot number. Here, we test whether the male behavioural courtship display (bobbing while waving a grass stem) correlates with male spot number and pairing success. We also test whether male spot number predicts the outcome (winner or loser) of intrasexual competition over courtship materials (grass stem, perch, nest site). Males with many spots had higher pairing success, and male spot number correlated with the intensity of courtship display. In a multivariate statistical analysis, male courtship display was the stronger predictor of male pairing success. Finally, male spot number predicted the outcome of intrasexual interactions: males with many spots consistently won contests over grass stems, perches and nest sites. We suggest that intrasexual selection could favour male spot number, whereas courtship intensity appears to be under stronger intersexual selectio
Maternal Investment in Diamond FiretailsStagonopleura guttata: Female Spot Numbers Predict Egg Volume and Yolk Lutein Content
No full textIt is widely known that parents invest into reproduction to increase offspring survival and thereby increase reproductive success. In particular, female birds allocate maternal resources including lipids, hormones, and nutrients into the egg yolk. Carotenoid pigments, which are responsible for the characteristic yellow, orange, and red colours, are particularly important as antioxidant for the developing embryo. The Investment Hypothesis addresses variable female allocation of maternal resources into egg yolk and predicts that high quality females and females paired to high-quality males will invest more in their eggs. We test predictions of the Investment Hypothesis in the Diamond Firetail Stagonopleura guttata. In captive females and their pair males, we compare yolk carotenoid (lutein and zeaxanthin) allocation and egg size in relation to traits indicative of individual quality (body condition, flank spot number, bill and rump colour). Females with more white flank spots laid larger eggs that contained more lutein, the major carotenoid found in the Diamond Firetail eggs. Total carotenoid concentration in egg yolk was not related to any other female characteristic. Females laid larger eggs when paired with a high quality male (dark red rump)
White Flank Spots Signal Feeding Dominance in Female Diamond Firetails, Stagonopleura guttata
No full textPlumage colour can be used as an honest signal to convey health and status, which has traditionally been examined in the sexual selection context of choosy females and elaborate males. We use a model avian system to study the role of plumage coloration in a social context such as inter- and intrasexual competition over food resources. The diamond firetail (Stagonopleura guttata) is an endemic Australian finch: females have more white flank spots than males, and white spot number was correlated with cell-mediated immune response in females. We use two experimental designs to test the role of white flank spots for feeding dominance and dominance discrimination in a group-living bird. The results from two-choice trials and from single-arena trials showed that female ornamentation was consistently important in social food contests, and males consistently responded to female spot number. Females with higher spot number fed first, in trials with males and/or females. Also, females preferred to feed next to test birds with low spot number, but males showed no preference for feeding next to birds with few or many spots. Finally, latency to feed was predicted by spot number: both males and females had longer latency to feed if test birds had more spots than the focal birds. We conclude that female, but not male, ornamentation was important for inter- and intrasexual food competition. This is one of the very few studies to show that the same plumage ornament can have a different function between the sexes as a signal of social status. Moreover, this study shows that white plumage can be a signal of dominance
When subspecies matter: resident Superb Fairy-wrens (Malurus cyaneus) distinguish the sex and subspecies of intruding birds
No full textThe widely accepted functions of complex bird song - to defend a territory or attract a mate, or both - have generally been tested in northern hemisphere species in which males produce the song and females choose the singer. In our study species, the Superb Fairy-wren (Malurus cyaneus), both males and females sing a solo song throughout the year. We compare the chatter song in males and females of two genetically distinct subspecies, and test if resident birds respond to the sex and subspecies of the intruder song. Compared with island birds (M. c. ashbyi), mainland Superb Fairy-wrens (M. c. leggei) produced songs with lower frequency and fewer elements. Compared with females, males produced longer songs with more elements. Resident birds showed acoustical discrimination for the sex and subspecies of the intruder bird. The response of resident pairs was positively correlated, but each sex showed a solo response. Resident males were the first to respond to male intruders, and resident females were the first to respond to female intruders. Fairy-wrens had the strongest response towards (1) intruders of the same subspecies and (2) male intruders. The finding of signal divergence and acoustical discrimination in males and females makes this a model system to test the mechanism of reproductive isolation when both sexes sing
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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