Aspects Of Individual Quality Research Articles

A practical approach to measuring the acoustic diversity by community ecology methods

Abstract The study of the diversity of animal signals on within‐ and among‐species levels is the key to uncover mechanisms that shape the evolution of communication systems. However, the methods used to quantify acoustic diversity (like repertoire size) lack to grasp several aspects of acoustic diversity. Here, we propose a new framework for the study of animal communication, in which we decompose the acoustic diversity with the methodological toolbox from community ecology. We explore how different diversity estimates reflecting different aspects of acoustic diversity can be applied to characterise the complexity of acoustic signals. We propose that this approach can be used in a wide range of animal taxa to derive further insights about the function and evolution of communication systems besides the traditional methods. To illustrate the use of our approach in a case study, we used the song of the collared flycatcher Ficedula albicollis as model system. Based on three frequency and time variables, we calculated three functional diversity indices (FRic, FEve and FDiv) to characterise the distribution of song elements (syllables) in the acoustic parameter space. We aimed to uncover the interrelations of diversity indices, reveal the degree of among‐individual consistency and investigate their relationships with certain aspects of individual quality (body condition, age and arrival date). We found that the diversity indices were largely independent of each other and showed different consistency patterns that were time‐scale dependent, indicating different signalling potential of individual‐specific attributes. We also found that FEve strongly related to the age of males. Our case study showed that decomposing the diversity into different components can reveal additional biologically meaningful aspects of birdsong.

Multiple signals predict male mating success in the lek-mating lesser prairie-chicken (Tympanuchus pallidicinctus)

Sexual selection theory maintains that traits under selection honestly advertise qualities of signaling individuals and that only individuals in the best condition can survive while displaying maximally elaborated secondary sexual ornaments. Recent trends in mate choice studies have favored the consideration of the effects of multiple traits on mating success, including suites of traits transmitted in different sensory modalities. Sexual selection is expected to be especially strong in lek-mating species. The lesser prairie-chicken (Tympanuchus pallidicinctus) is a grouse species which breeds on leks. Males of this species perform audio and locomotor displays and exhibit two pairs of brightly colored ornaments. We performed an observational study of mate choice in spring 2016–2018 and noted 40 copulations on seven leks. We quantified behavioral, territorial, and morphological characteristics of males along with ornament color properties. We found that variables from all categories considered predicted female choice. Age had the strongest effect, with adult males experiencing higher female choice relative to yearlings. Allocation of aggressive behavior and comb color properties were also strongly correlated with female choice. Our results show that modulating behavior depending on whether females are present contributes to male mating success and highlight the importance of the size and color properties of secondary ornaments. Further research is required to determine how the variables most strongly associated with mate choice relate to one another and which aspects of individual quality, if any, are signaled by color ornaments. Future studies could also incorporate variables related to females to determine if selection on females occurs. The choice of a mate can help determine the survival and reproductive success of offspring. In species where males do not care for offspring, mate choice can be highly consistent among females, and mate choice decisions are often based on the evaluation of multiple traits such as vocalizations, behavior, and morphological trait size. Based on measurements of captured males and observations of breeding behavior, we demonstrate that mate choice in lesser prairie-chickens (Tympanuchus pallidicinctus) correlates with male behavior, morphology, skin patch color, and territorial characteristics. Our findings represent a rare demonstration of mating success being influenced by how male behavior (including aggression) changes when females are present or absent. Our results show how multiple traits can transmit information about individual quality and support theoretical links between mate choice and increased male age or male-male competition.

Unravelling the relationships between life history, behaviour and condition under the pace-of-life syndromes hypothesis using long-term data from a wild bird

The hypothesis of pace-of-life syndromes (POLS) predicts relationships between traits including life history traits and risk-taking behaviour that can be mediated by the trade-off between current and future reproductive value. However, alternative causal mechanisms may also generate covariance among these traits without trade-offs. We investigated the relationships between survival to the next year, current reproductive investment and risk-taking behaviour (flight initiation distance) in male collared flycatchers, Ficedula albicollis, using long-term data. We used structural equation modelling (SEM) to uncover whether the associations among traits are mediated by a common latent factor that determines how individuals balance the trade-off between current and future reproductive value. As trade-offs could be concealed when there are differences in resource acquisition between individuals, we also included potential causes of these differences, body mass and body size, in the analysis. We found that risk-taking behaviour was positively related to reproductive investment and negatively to survival to the next year as could be predicted if investment into a risky behaviour is traded against future prospects. However, the most supported SEM model also suggested that survival to the next year was positively related to current reproductive investment, contrary to predictions of a hypothesis based on trade-off. These results remained qualitatively similar when controlling for body condition. In conclusion, we only could derive partial support for the POLS hypothesis. We suggest that aspects of individual quality, and not only trade-offs, should also be considered when interpreting the relationships between life history and behavioural traits. We investigated the association between two life history components (survival to the next year and current reproductive effort) and risk-taking behaviour, relying on long-term records from a passerine bird, to investigate the predictions of the pace-of-life syndrome (POLS) hypothesis. Using structural equation modelling, we found support for a causal model that implies that risk-taking negatively affects survival to the next year and that survival to the next year and current reproductive effort are strongly and positively associated. Controlling for the effect of body condition did not fundamentally change these relationships. We could not find conclusive evidence for the investigated traits being mediated by a common underlying factor, as generally predicted by the POLS hypothesis. However, the sign of the relationship between risk-taking behaviour and survival to the next year was as predicted by the POLS hypothesis.

The role of the mating system and intraspecific brood parasitism in the costs of reproduction in a passerine bird.

Limited resources trigger trade-offs in resource allocation. Reproduction is one of the most demanding activities in terms of energy, and costs related to reproduction can be apparent either as reduced future reproduction or as survival. However, costs are not always detected, because individual heterogeneity in quality and resource acquisition may explain variation in costs among individuals. We conducted a comprehensive study in spotless starlings (Sturnus unicolor) nesting in Central Spain to determine whether costs of reproduction could be detectable in the short and/or long term and whether prenatal or postnatal investment were driving these costs. We took into account the lifehistory of the species, where egg volume is highly repeatable, males are facultatively polygynous, and intraspecific brood parasitism occurs. Females with a high reproductive effort in a breeding event also had a high reproductive effort in the second event of the season. The mating system and maternal age were reliable predictors of breeding success within a breeding event: monogamous and primary females, as well as older mothers, raised more nestlings than secondary females and 1-year-old females, respectively. However, when high-investing females suffered intra-brood parasitism in 1 year, we found a negative correlation between current and futurereproduction. These results suggest that, under some circumstances, females are able to skip the short-term costs of reproduction, but when extra effort is added, trade-offs arise. While most studies have focused on different aspects of individual quality on costs, the ecological context seems to represent an important component that should be taken into account.

Bill colour pattern in Bewick’s swan: information on sex and body size displayed on face?

Ornamental traits in birds (plumage/bare part colours) have been shown to provide information on diverse aspects of individual quality and behaviour. In bird species with achromatic plumages (uniformly white, grey or black), signals encoded in bare parts are the major mode of visual communication. In this study we analysed the influence of sex, age, body condition and selected biometric traits on the bill colour pattern in Bewick’s swans Cygnus columbianus bewickii. The results indicate that sex and body size (weight and tarsus length) are associated with the bill colour pattern in Bewick’s swans. Individuals with a larger black area on the bill were heavier and had a longer tarsus. Moreover, females had more black on their bills than males did. Age, head length and body condition index were not significantly related to bill colour pattern. The present work indicates that Bewick’s swans may display information on their sex and size by means of their bill colour pattern. These findings also suggest the possibility that swans can remotely quantify one another’s traits from the appearance of their bill colouration. Proper assessment of an opponent or of mate quality during face-to-face signalling may help birds to avoid unnecessary interaction or to maintain bonds between mates and family groups.

Evolutionary trade-off between naturally- and sexually-selected melanin-based colour traits in worldwide barn owls and allies

Natural selection typically constrains the evolution of sexually-selected characters. The evolution of naturally- and sexually-selected traits can be intertwined if they share part of their genetic machinery or if sex traits impair foraging success or increase the risk of depredation. The present study investigated phenotypic correlations between naturally- and sexually-selected plumage traits in the Tytonidae (barn owls, grass owls, and masked owls). Phenotypic correlations indicate the extent to which selection on one trait will indirectly influence the evolution of another trait. In this group of birds, the ventral body side varies from white to dark reddish, a naturally-selected pheomelanin-based colour trait with important roles in predator–prey interactions. Owls also exhibit eumelanin-based black spots, for which number and size signal different aspects of individual quality and are used in mate choice. These three plumage traits are strongly heritable and sexually dimorphic, with females being on average darker reddish and more spotted than males. Phenotypic correlations were measured between these three plumage traits in 3958 free-living barn owls in Switzerland and 10 670 skin specimens from 34 Tyto taxa preserved in museums. Across Tyto taxa, the sexually-selected plumage spottiness was positively correlated with the naturally-selected reddish coloration, with redder birds being more heavily spotted. This suggests that they are genetically constrained or that natural and sexual selection are not antagonistically exerted on plumage traits. In a large sample of Swiss nestlings and within 34 Tyto taxa, the three plumage traits were positively correlated. The production of melanin pigments for one plumage trait is therefore not traded off against the production of melanin pigments for another plumage trait. Only in the most heavily-spotted Tyto taxa do larger-spotted individuals display fewer spots. This indicates that, at some threshold value, the evolution of many spots constrains the evolution of large spots. These analyses raise the possibility that different combinations of melanin-based plumage traits may not be selectively equivalent.

Female Performance of Male Courtship Display in Northern Cardinals

Abstract Courtship behaviors in birds are often considered male-specific, as males compete for mates through displays that exhibit individual quality. Several courtship displays have been described for male Northern Cardinals including the complex song-dance display. We observed female cardinals performing the song-dance display on two separate occasions in south Mississippi within pre-breeding and breeding periods. Female performance of the display was very similar as reported for males. Given the behavioral attributes of cardinal mating pairs, it is plausible that bi-directional mate choice exists for this species and females are demonstrating aspects of individual quality to males through the song-dance display. Additional monitoring of courtship behavior is needed to determine the function of female performance display that was previously thought to be male specific.

Integrated plumage colour variation in relation to body condition, reproductive investment and laying date in the collared flycatcher

The possible integration of different sexual ornaments into a composite system, and especially the information content of such ornament complexes, is poorly investigated. Many bird species display complex plumage coloration, but whether this represents one integrated or several independent sexual traits can be unclear. Collared flycatchers (Ficedula albicollis) display melanised and depigmented plumage areas, and the spectral features (brightness and UV chroma) of these are correlated with each other across the plumage. In a 5-year dataset of male and female plumage reflectance, we examined some of the potential information content of integrated, plumage-level colour attributes by estimating their relationships to previous and current year body condition, laying date and clutch size. Females were in better condition the year before they became darker pigmented, and males in better current year condition were also darker pigmented. Female pigment-based brightness was positively, while male structurally based brightness was negatively related to current laying date. Finally, the overall UV chroma of white plumage areas in males was positively associated with current clutch size. Our results show that higher degree of pigmentation is related to better condition, while the structural colour component is associated with some aspects of reproductive investment. These results highlight the possibility that correlated aspects of a multiple plumage ornamentation system may reflect together some aspects of individual quality, thereby functioning as a composite signal.

Environmental and Genetic Effects on Pigment-Based vs. Structural Component of Yellow Feather Colouration

BackgroundCarotenoid plumage is of widespread use in bird communication. Carotenoid-based feather colouration has recently been shown to be dependent on both pigment concentration and feather structure. If these two components are determined differently, one plumage patch may potentially convey different aspects of individual quality.Methodology/Principal FindingsWe evaluated the effects of genetic and environmental factors on carotenoid-based yellow breast colouration of Great Tit (Parus major) nestlings. By partial cross-fostering, we separated the genetic and pre-natal vs. post-natal parental effects on both the structural and the pigment-based component of carotenoid-based plumage colouration. We also simultaneously manipulated the post-hatching environment by brood size manipulation. The structural component of nestling colouration reflected features of female colouration. On the other hand, the pigment-based component was more affected by rearing conditions presumably representing food quality. While the structural component was related to both origin- and environment-related factors, the pigment-based component seemed to be environment-dependent only. These results support the notion that pigment-based and structural components of feather colouration are determined differently.Conclusions/SignificanceChromatic and achromatic components of carotenoid-based feather colouration reflected different aspects of individual quality and history, and thus may potentially form a multicomponent signal.

Plumage coloration predicts paternity and polygyny in the American redstart

Many animals display multiple signals that can be used by conspecifics to gather information about the condition or quality of potential mates or competitors. Different signals can indicate different aspects of individual quality or function in spatially or temporally separated periods. However, for long-distance migratory birds, it is unclear if signals, such as plumage traits, function in different phases of the annual cycle. We investigated the potential role of carotenoid-based tail and flank plumage, and bib size, in relation to extrapair paternity and polygyny in the American redstart, Setophaga ruticilla. This work complements our previous research suggesting tail feather brightness acts as a status signal, mediating territory acquisition during the nonbreeding season in Jamaica. Here, we show that tail feather brightness also serves as an important signal during the breeding season. Specifically, our results indicate that polygyny, a behaviour highly dependent on obtaining and defending multiple territories, is significantly predicted by tail brightness. Interestingly, flank redness best predicted whether individuals secured paternity at their nest and the proportion of within-pair offspring sired. We suggest that by expanding the study of plumage function in long-distance migrants to events occurring throughout the annual cycle, we gain a critical perspective on the function and evolution of ornamental traits.

Age‐related differences in plumage characteristics of male tree swallows Tachycineta bicolor: hue and brightness signal different aspects of individual quality

Age‐related differences in plumage characteristics of birds can be the result of differential survival of more ornamented individuals, within‐individual changes in plumage attributes with age, or a combination of both. In this study, we investigated age‐class related differences in plumage attributes of male tree swallows Tachycineta bicolor by performing both cross‐sectional and longitudinal analyses. Male tree swallows in their first breeding season do not display delayed plumage maturation, and possess, like experienced breeders, metallic green to metallic blue iridescent plumage on their dorsal surface. Our results showed that, at the population level, older males were brighter and reflected light maximally at shorter wavelengths (i.e. were more blue). Differences in plumage brightness were most likely caused by changes within individuals as males increased in brightness between the first time they were captured and the subsequent year. Differences in hue, however, were not due to within‐individual changes, but rather appear to be the result of greener individuals having lower survival and/or nest site fidelity. Indeed, relatively dull, greener birds had a lower probability of being recaptured the subsequent year. In contrast, we found that if birds captured in their first year as breeding adults were relatively bright, hue was not related to the probability of recapture. These results suggest that plumage attributes in male tree swallows have the potential of being honest signals of quality. Furthermore, plumage brightness and plumage hue might signal different aspects of male quality in this species.

Quality assessment and comparison of grading between examiners and supervisors of Bachelor theses in nursing education

This study compares supervisors' and examiners' grading of quality of theses at Bachelor level in nursing. An instrument developed to asses the quality of theses was used. Eight aspects of quality were rated. One hundred and fifteen theses were rated by both examiner and supervisor. Significant correlations were found between examiners' and supervisors' ratings of all aspects of quality. Good agreement was found in 89-96% of the ratings on individual aspects of quality. The means of differences between ratings were small but significantly differed from zero in four out of eight aspects. In theses rated low for quality of language and formality, differences between examiners' and supervisors' ratings on all aspects of quality were significantly larger than in theses rated high for quality of language and formality. The general conclusion is that the evaluations made by examiners and by supervisors corresponded well. Differences found indicates that examiners in general give lower scores than supervisors especially on quality aspects that are most closely related to research methods and experiences. This study is part of a larger project that is investigating quality of theses and the student's attitudes and learning experiences of writing theses.

Melanin pigmentation negatively correlates with plumage preening effort in barn owls

SummaryAccording to the handicap principle of sexual selection, colourful ornaments honestly signal absolute quality only if they entail fitness costs. The degree of melanism often covaries positively with aspects of individual quality, and hence melanin‐based coloration should be costly to produce or to maintain in a good shape. This is, however, unlikely because melanin‐based coloration is often strongly heritable and in birds the rate of feather wear decreases with the amount of melanin pigments packed in feathers.The hypothesis that melanin pigments reduce the cost of maintaining colourful ornaments in a good shape predicts a negative correlation between the degree of melanism and both the size of the uropygial gland that produces preening secretions and the intensity of preening behaviour.Using a correlative approach, I evaluated these two predictions in the barn owlTyto albain which the body underside varies from immaculate to heavily marked with black spots, a eumelanin‐based trait, and from white to reddish‐brown, a phaeomelanin‐based trait. I correlated plumage traits with preening behaviour in nestlings and with the size and mass of the uropygial gland in dead adults. I also weighed nonornamental wing and tail feathers to assess whether the quality of nonornamental feathers is positively correlated with the degree of melanism of an ornamental plumage trait.The degree of phaeomelanism was neither associated with preening behaviour nor with the size and mass of the uropygial gland. In line with the two predictions, individuals with more and larger black spots had a lighter uropygial gland and preened less frequently. Because nonornamental wing and tail feathers of spottier individuals were heavier per unit of surface area, the entire plumage of eumelanic individuals may be more robust and in turn require less care than the plumage of nonmelanic conspecifics.In conclusion, the degree of eumelanism can be associated with aspects of individual quality even if eumelanic ornaments are neither costly to produce nor to maintain in a good shape.

Why do melanin ornaments signal individual quality? Insights from metal element analysis of barn owl feathers.

Melanin-based variation in colour patterns is under strong genetic control and not, or weakly, sensitive to the environment and body condition. Current signalling theory predicts that such traits may not signal honestly phenotypic quality because their production does not entail a significant fitness cost. However, recent studies revealed that in several bird species melanin-based traits covary with phenotypic attributes. In a first move to understand whether such covariations have a physiological basis, we quantified concentrations of five chemical elements in two pigmented plumage traits in the barn owl (Tyto alba). This bird shows continuous variation from immaculate to heavily marked with black spots (plumage spottiness) and from dark reddish-brown to white (plumage coloration), two traits that signal various aspects of individual quality. These two traits are sexually dimorphic with females being spottier and darker coloured than males. We found an enhancement in calcium and zinc concentration within black spots compared with the unspotted feather parts. The degree to which birds were spotted was positively correlated with calcium concentration within spots, whereas the unspotted feather parts of darker reddish-brown birds were more concentrated in zinc. This suggests that two different pigments are responsible for plumage spottiness and plumage coloration. We discuss the implications of our results in light of recent experimental field studies showing that female spottiness signals offspring humoral response towards an artificially administrated antigen, parasite resistance and fluctuating asymmetry of wing feathers.