122 research outputs found

    Effect of timing and female quality on clutch size in the Collared Flycatcher Ficedula albicollis

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    Capsule: Laying date and female age appear to be related to clutch size. Aims: To test two hypotheses ('date' and 'quality'), which might explain why fewer eggs are laid late in the season. Methods: Four years of data and multivariate analysis were used to test the effects of timing of breeding and female quality reflected by morphological variables and age on clutch size in the Collared Flycatcher Ficedula albicollis. We estimated food supply during parental care by measuring diet composition of nestlings. Results: We distinguished the independent effects of date and age of females on clutch size. The type of prey fed to nestlings was different early and late in the season. Hence food supply during the nestling care period may be a limiting environmental factor that indirectly determines clutch size. Conclusion: Our results are consistent with the predictions of the date hypothesis, but the quality hypothesis was also partially supported. Depending on year effects, 30-50% of the variance in clutch size may be related to the timing of breeding and an additional 5-10% may be due to quality (age) differences between early- and late-breeding birds

    Depigmented wing patch size is a condition-dependent indicator of viability in male collared flycatchers

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    Honesty of sexual advertisement is thought to be the result of signalling costs. Because production costs of depigmented plumage patches are probably very low, their role as honest signals of individual quality has been questioned. Costs of bearing these traits, however, should also be taken into account. Studies on proximate determination and possible information content of white badges are very rare. We investigated repeatability, sensu lato heritability, and condition- and age-dependence of white wing patch size, a male display trait in a population of collared flycatchers (Ficedula albicollis), based on 4 years of data. By comparing relationships between age and wing patch size (1) within individuals among years versus (2) among individuals within years, we could address the viability indicator value of the trait. Wing patch size approximately doubled at the transition from subadult to adult plumage, and its change was significantly related to body condition the previous season. Repeatability and heritability values suggest that the trait is informative already in subadult plumage, and that genetic and early environmental effects are important in its determination, the latter only during the first year of life. Thus, wing patch size can act as a condition-dependent signal of genetic quality. Indeed, discrepancy between results from the horizontal and vertical age-dependence approaches shows that the trait was positively related to expected lifespan. After examining several alternative explanations, we conclude that wing patch size indicates genetically based viability. This is the first study to demonstrate a good genes viability benefit conferred by a depigmented plumage patch

    Avian Song Complexity is Associated With High Field Metabolic Rate

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    Question: Is the production of bird song costly? Analyses of oxygen consumption during singing provided conflicting results. Data studied: Data on 28 passerine species with quantitative information on song complexity and field metabolic rate, which reflects energy requirements of wild birds. The phylogenetic relationship data came from molecular sources. Search method: Generalized least squares models to control for phylogenetic associations. First, we adjusted field metabolic rate to body size, and calculated the phylogenetic correlation between relative field metabolic rate and measures of song complexity. Second, we compared song complexity of birds inhabiting and and mesic environments. Conclusion: A measure of short-term song complexity, relative syllable repertoire size, is positively and significantly related to relative field metabolic rate. Species from and habitats have less complex songs than species from mesic habitats

    Sexually size dimorphic brains and song complexity in passerine birds

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    Neural 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

    Dynamics of multiple sexual signals in relation to climatic conditions

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    Question: Can trait-specific phenotypic plasticity in response to annual environmental variation lead to changes in the strength of sexual selection through the relative expression of sexual ornaments at the population level? Data description: We recorded breeding dates and the sizes of white forehead and wing patches of male collared flycatchers (Ficedula albicollis) from 1998 to 2005 in a nestboxbreeding population in the Pilis Mountains, Hungary. As environmental predictors, we used the North Atlantic Oscillation (NAO) index and local weather data, classified as direct or indirect effects relative to the moult of the given ornament. Search method: First, we used general linear mixed models to assess environmental effects on the within-individual changes and absolute yearly sizes of forehead and wing patches. We then used similar models to determine whether the relative sizes of the two plumage traits at the population level varied among years. Finally, we used multiple regressions to establish if the relative yearly expression of an ornament affected standardized sexual selection gradients on this ornament in the given year. Conclusions: Within-individual changes in forehead and wing patch size were predicted by the climate of their moulting season (winter and summer, respectively). There was also an indirect effect of previous winter climate on changes in wing patch size. Environmental effects on the absolute expression of ornaments at the population level followed the within-individual patterns. The relative population-level expression of forehead and wing patches fluctuated significantly among years. Sexual selection on a given ornament increased with its relative expression in that year

    Latitudinal distribution, migration, and testosterone levels in birds

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    Tropical bird species usually have lower testosterone (T) levels during breeding than temperate species. However, the potential mechanisms behind the positive interspecific correlation between T and latitude remain unexplored. In a comparative study of more than 100 bird species, we examined whether social constraints during male-male competition arising from migration and breeding synchrony are responsible for the latitude effects. Species that breed at higher latitudes are more likely to migrate and experience more intense intrasexual competition upon spring arrival than nonmigrant species from lower atitudes. Additionally, species from higher latitudes cope with shorter breeding seasons and thus with more synchronous breeding, which selects for high T titers via increased male-male conflicts. Accordingly, peak T levels were associated with migration and the duration of the egg laying period that reflects breeding synchrony. Because migration and breeding synchrony were related to latitudinal distribution, they appear to be important components of the latitude effects on T. A multivariate model controlling for covariation of predictor variables revealed that latitude remained the strongest predictor of peak T. Therefore, selection due to migration and breeding synchrony may partially cause the latitude effect, but other geographically varying factors may also play a role in mediating peak T levels at different latitudes

    Roll with the fear: environment and state dependence of pill bug (Armadillidium vulgare) personalities

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    Most studies on animal personality evaluate individual mean behaviour to describe individual behavioural strategy, while often neglecting behavioural variability on the within-individual level. However, within-individual behavioural plasticity (variation induced by environment) and within-individual residual variation (regulatory behavioural precision) are recognized as biologically valid components of individual behaviour, but the evolutionary ecology of these components is still less understood. Here, we tested whether behaviour of common pill bugs (Armadillidium vulgare) differs on the among- and within-individual level and whether it is affected by various individual specific state-related traits (sex, size and Wolbachia infection). To this aim, we assayed risk-taking in familiar vs. unfamiliar environments 30 times along 38 days and applied double modelling statistical technique to handle the complex hierarchical structure for both individual-specific trait means and variances. We found that there are significant among-individual differences not only in mean risk-taking behaviour but also in environment- and time-induced behavioural plasticity and residual variation. Wolbachia-infected individuals took less risk than healthy conspecifics; in addition, individuals became more risk-averse with time. Residual variation decreased with time, and individuals expressed higher residual variation in the unfamiliar environment. Further, sensitization was stronger in females and in larger individuals in general. Our results suggest that among-individual variation, behavioural plasticity and residual variation are all (i) biologically relevant components of an individual’s behavioural strategy and (ii) responsive to changes in environment or labile state variables. We propose pill bugs as promising models for personality research due to the relative ease of getting repeated behavioural measurements

    Egy összetett szignalizációs mechanizmus: a madárének lokális, regionális és evolúciós mintázatai = Bird song as a multiple functioning sexual signal: patterns on individual, population and regional levels

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    Tervezett vizsgálataink célja egy komplex, ivarilag szelekctált szignál, a madárének funkcionális kapcsolatrendszereinek felderítése volt. Különböző szinteken, egyedektől a poulációs szinten keresztül a fajok közötti kapcsolatokig vizsgáltuk a szignál információ tartalmát és annak szerepét az ivari kiválasztódás és a természetes szelekció folyamatában. Terepi vizsgálataink bizonyították, hogy az ének különböző paraméterei az egyedi minőség más és más komponensét (parazitáltság, kor, stressz-tolerancia, személyiség) jelzik. Kimutattuk továbbá az ének szerepét a hím-hím versengésben valamint a hölgyválasz mechanizmusában. Populációs szintű vizsgálatainkban szimpatrikusan és allopatrikusan élő légykapók énekszegregációját elemeztuk az együttélés időskáláját is figyelembe véve. Modern komparatív analízisekkel interspecifikus kapcsolatot tártunk fel az ének összetettsége és az agyméret közötti, míg heterospecifikus vokális mimikri evolúcióját is vizsgáltuk. A kutatás során egy általunk először alkalmazott repertoárméret-becslő módszer fejlesztését is folytattuk egy nemzetközi kooperáció keretén belül. Eredményeinket nemzetközileg elismert folyoíratokban publikáltiuk. | The aim of the planned research was to investigate the functional relationships of a complex, sexually selected trait, namely bird song. We studied the information content of the signal, and its roles in sexual and natural selection by focusing on three organizational levels, such as individuals, populations and species. Our field research with the collared flycatcher (Ficedula albicollis) proved that different characteristics of the song signal different aspects of male quality (parasite load, age, stress-tolerance and personality). We also found that the song plays role in male-male competition and female choice. Comparisons of sympatric and allopatric populations of flycatchers in Europe revealed evidence for the segregation of song depending on the duration of the evolutionary contact. By using modern comparative methods, we failed to demonstrate an interspecific relationship between bird song and speciation, but discovered that the complexity of songs is evolutionary related to brain dimorphism between sexes. We also demonstrated some evolutionary patterns in association with heterospecific vocal mimicry. During this research, we developed a new method for estimating repertoire size. Our results have been published in the leading journals of the field

    Döntési mechanizmusok a madarak viselkedésökológiájában: anyai eredetű biomolekulák környezetfüggő átvitele a petesejtbe = Decision marking in behaviour ecology of birds: maternal preference

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    Az öröklött tulajdonságok mellett az utódok rátermettségét a korai környezeti (anyai) hatások jelentősen módosíthatják. Madaraknál vizsgáltuk, hogy a tojó által a tojásba juttatott anyagok (ivari hormonok, vitaminok, karotinoidok, immunanyagok) hogyan segítik a fiókák fejlődését ill. az anyagok allokációs mintázatát milyen (proximális és ultimális) változók magyarázhatják. Megállapítottuk, hogy az örvös légykapónál a tojásméretet a környezeti tényezők és a tojó minősége, a tojás IgG-szintjét a tojó minősége prediktálta. A karotinoidok, az E- és A-vitamin, valamint a biliverdin (tojáshéj pigment) deponálása a tojó párjának korától függött. Kompenzációs mechanizmusra utal, hogy a tapasztalatlan fiatal hímek fészekaljaiban a tojók növelték a tesztoszteront és az antioxidánsokat. Kísérletesen bizonyítottuk, hogy a tesztoszteron depozíciójára hat, a karotinoidok és az IgG depozíciójára viszont nem hat a szociális környezet változása. Az örvös légykapó tojások biopsziás vizsgálataiból és japánfürj tojások hormonkoncentrációjának kísérletes megemeléséből arra következtethetünk, hogy a tojásokban lévő androgének (T, A4, DHT) rövid távon eltérően hatnak az utódok rátermettségére. A kék cinegéknél pozitív kapcsolatot találtunk a hímek egy ivari szignálja (fejtető UV visszaverése) és a tojások becsült karotinoidmennyisége között. Végül a széncinege többszörös ivari szignalizációját elemezve rámutattunk a szignalizáció és az anyai hatások környezetfüggőségére. | In addition to genetic effects, the fitness of offspring is considerably modified by early environmental (maternal) effects. We examined how egg constituents deposited by the female (sexual hormones, vitamins, carotenoids, immune mediators) help offspring development and what proximate and ultimate factors may explain the allocation pattern of these substances. In the collared flycatcher we found that egg size was predicted by environmental factors and female quality, while IgG level by the quality of the female. The deposition of carotenoids, biliverdin, vitamins A and E depended on the characteristics of the female's mate. Consistent with a compensation mechanism, females increased the concentration of egg testosterone and antioxidants in clutches laid for inexperienced young males. We experimentally demonstrated that changing social environment modifies the deposition of testosterone but not that of carotene metabolites and IgG. By conducting biopsy studies of collared flycatcher eggs and experimentally elevating sex steroid levels in Japanese quail eggs, we found that different androgens in the egg (T, A4, DHT) have different short term effects on offspring fitness. In blue tits, we found a positive relationship between a sexual signal of males (crown UV reflectance) and the estimated carotenoid levels of eggs. Finally, analyses of multiple sexual signals in great tits indicated the environment-dependence of signalization and maternal effects
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