Abstract: Avian wing length is an important trait that covaries with the ecology and migratory behaviour of a species and tends to change rapidly when the conditions are altered. Long-distance migrants typically have longer wings than short-distance migrants and sedentary species, and long-winged species also tend to be more dispersive. Although the substantial heritability of avian wing length is well established, the identification of causal genes has remained elusive. Based on large-scale genotyping of 1404 informative single nucleotide polymorphisms (SNP) in a captive population of 1067 zebra finches, we here show that the within-population variation of relative wing length (h2 = 0.74 ± 0.05) is associated with standing genetic variation in at least six genomic regions (one genomewide significant and five suggestive). The variance explained by these six quantitative trait loci (QTL) sums to 36.8% of the phenotypic variance (half of the additive genetic variance), although this likely is an overestimate attributable to the Beavis effect. As avian wing length is primarily determined by the length of the primary feathers, we then searched for candidate genes that are related to feather growth. Interestingly, all of the QTL signals co-locate with Wnt growth factors and closely interacting genes (Wnt3a, Wnt5a, Wnt6, Wnt7a, Wnt9a, RhoU and RhoV). Our findings therefore suggest that standing genetic variation in the Wnt genes might be linked to avian wing morphology,
although there are many other genes that also fall within the confidence regions.
Abstract: Mate choice based on sexual ornaments can impose strong selection, which raises the question of how genetic variation in ornaments is maintained. One mechanism that has been proposed is genic capture. If ornament expression is influenced by general condition and condition is under polygenic control, selection will be inefficient in removing genetic variation. Here we analyze whether the genetic architecture of beak color in a population of zebra finches supports this hypothesis. Zebra finch beak color is commonly assumed to be under strong selection by mate choice, although some of the evidence is ambiguous. We show that beak redness has a heritability of 34% in our population and that it is strongly genetically correlated between the sexes, suggesting that it is largely controlled by the same genes in males and females. We mapped variation in beak redness based on 1,404 SNP markers genotyped in a large pedigree. We find evidence for linkage on four chromosomes (Tgu1, Tgu5, Tgu13, Tgu21), which together explain a large part of the additive genetic variance. Our finding of genomic regions with major additive effects is not consistent with directional selection and genic capture, but rather suggests a role of antagonistic pleiotropy in maintaining genetic variation.
Abstract: Song is used as a signal in sexual selection in a wide range of taxa. In birds, males of many species continue to sing after pair formation. It has been suggested that a high song output after pair formation might serve to attract extrapair females and to minimise their own partner’s interest in extra-pair copulations. A non-exclusive alternative function that has received only scant attention is that the amount of song might stimulate the own female’s investment into eggs in a quantitative way. We address these hypotheses in a captive population of zebra finches, Taeniopygia guttata, by relating male undirected song output (i.e. non-courtship song) to male egg siring success and female reproductive investment in two different set-ups. When allowed to breed in aviaries, males with the highest song output were no more attractive than others to females in an analysis of 4,294 extra-pair courtships involving 164 different males, and they also did not sire more offspring (both trends were against the expectation). When breeding in cages with two different partners subsequently, females produced larger eggs with more orange yolks when paired to a male with a high song output. These findings suggest that singing activity in paired zebra finch males might primarily function to stimulate the partner and not to attract extra-pair females.
Abstract: Fitting generalised linear models (GLMs) with more than one predictor has become the standard method of analysis in evolutionary and behavioural research. Often, GLMs are used for exploratory data analysis, where one starts with a complex full model including interaction terms and then simplifies by removing non-significant terms. While this approach can be useful, it is problematic if significant effects are interpreted as if they arose from a single a priori hypothesis test. This is because model selection involves cryptic multiple hypothesis testing, a fact that has only rarely been acknowledged or quantified. We show that the probability of finding at least one ‘significant’ effect is high, even if all null hypotheses are true (e.g. 40% when starting with four predictors and their two-way interactions). This probability is close to theoretical expectations when the sample size (N) is large relative to the number of predictors including interactions (k). In contrast, type I error rates strongly exceed even those expectations when model simplification is applied to models that are over-fitted before simplification (low N/k ratio). The increase in false-positive results arises primarily from an overestimation of effect sizes among significant predictors, leading to upward-biased effect sizes that often cannot be reproduced in follow-up studies (‘the winner's curse’). Despite having their own problems, full model tests and P value adjustments can be used as a guide to how frequently type I errors arise by sampling variation alone. We favour the presentation of full models, since they best reflect the range of predictors investigated and ensure a balanced representation also of non-significant results.
Abstract: Consistent between-individual differences in context-general behavioral traits (often called personality traits) are particularly interesting for behavioral ecologists because they might show unexpected cross-context correlations and explain maladaptive behavior. In order to understand their evolutionary significance, it is relevant to know the heritability of these traits and how they relate to reproductive success. This might give insights into selective processes that maintain variation as well as into potential trade-offs. We scored approach to novel objects of 530 captive zebra finches in a familiar environment. Scores were highly repeatable and showed substantial additive genetic variation. We measured reproductive success, promiscuity, and extrapair paternity rates under aviary conditions and calculated linear and nonlinear selection differentials based on fertilization success as well as effects on chick-rearing success of pairs. Approach to novel objects had little influence on these components of reproductive success. However, we found that the social environment (manipulated operational sex ratios) influenced the correlation between approach to a novel object and the proportion of extrapair paternity. We also found that the sex ratio manipulation affected measures of the intensity of sexual selection. Both effects were stronger in males than in females. We conclude that despite the lack of differences in overall reproductive success, approach to novel objects reflects variation in reproductive strategies.
Abstract: Backgound. It is a common observation in evolutionary studies that larger, more ornamented or earlier breeding individuals have higher fitness, but that body size, ornamentation or breeding time does not change despite of sometimes substantial heritability for these traits. A possible explanation for this is that these traits do not causally affect fitness, but rather happen to be indirectly correlated with fitness via unmeasured non-heritable aspects of condition (e.g. undernourished offspring grow small and have low fitness as adults due to poor health). Whether this explanation applies to a specific case can be examined by decomposing the covariance between trait and fitness into its genetic and environmental components using pedigree-based animal models. We here examine different methods of doing this for a captive zebra finch population where male fitness was measured in communal aviaries in relation to three phenotypic traits (tarsus length, beak colour and song rate).
Results. Our case study illustrates how methods that regress fitness over breeding values for phenotypic traits yield biased estimates as well as anti-conservative standard errors. Hence, it is necessary to estimate the genetic and environmental covariances between trait and fitness directly from a bivariate model. This method, however, is very demanding in terms of sample sizes. In our study parameter estimates of selection gradients for tarsus were consistent with the hypothesis of environmentally induced bias (ßA = 0.035 ± 0.25 (SE), ßE = 0.57 ± 0.28 (SE)), yet this differences between genetic and environmental selection gradients falls short of statistical significance.
Conclusions. To examine the generality of the idea that phenotypic selection gradients for certain traits (like size) are consistently upwardly biased by environmental covariance a meta-analysis across study systems will be needed.
Abstract: In many species that form socially monogamous pair bonds, a considerable proportion of the offspring is sired by extrapair males. This observation has remained a puzzle for evolutionary biologists: although mating outside the pair bond can obviously increase the offspring production of males, the benefits of such behavior to females are less clear, yet females are known to actively solicit extrapair copulations. For more than two decades adaptionist explanations have dominated the discussions, yet remain controversial, and genetic constraint arguments have been dismissed without much consideration. An intriguing but still untested hypothesis states that extrapair mating behavior by females may be affected by the same genetic variants (alleles) as extrapairmating behavior bymales, such that the female behavior could evolve through indirect selection on the male behavior. Here we show that in the socially monogamous zebra finch, individual differences in extrapair mating behavior have a hereditary component. Intriguingly, this genetic basis is shared between the sexes, as shown by a strong genetic correlation between male and female measurements of extrapair mating behavior. Hence, positive selection on males to sire extrapair young will lead to increased extrapair mating by females as a correlated evolutionary response. This behavior leads to a fundamentally different view of female extrapair mating: it may exist even if females obtain no net benefit from it, simply because the corresponding alleles were positively selected in the male ancestors.
Notes: Evaluation at F1000 - http://f1000.com/11707957
Abstract: Although sleep is fundamental for survival, not much is known about sleep behaviour in free-living animals and between-individual variation in sleep patterns has hardly been studied, except in humans. We analysed sleep behaviour in a free-living population of blue tits in southern Germany. We recorded individuals roosting in nestboxes between November and April using infrared-sensitive cameras. We investigated the following sleep parameters: time of entering and leaving the nestbox, sleep onset, awakening time, sleep duration, midpoint of sleep, latency to sleep and frequency and duration of nocturnal awakenings. Sleep onset, awakening time and sleep duration followed seasonal changes in daylength. Blue tits slept ca. 4.8 h longer in winter than in spring. During the night, birds woke up between 23 and 230 times, but this did not change seasonally. Local light conditions influenced awakening time: birds at brighter locations woke up earlier. Females slept on average 15 min longer per night than males and this sex difference became more pronounced in early spring. Although females spent a greater proportion of the night awake than males, they still slept more overall. First-year birds spent more time in the nestbox after waking up and left the nestbox later in the morning than older individuals. Repeatability estimates showed that individuals were consistent in their sleep behaviour over the 2-year study period. Our results indicate that sleep patterns are individual-specific traits in blue tits. We suggest that the observed sex difference in sleep duration is caused by sexual selection.
Abstract: Background: Obtaining a draft genome sequence of the zebra finch (Taeniopygia guttata), the second bird genome to be sequenced, provides the necessary resource for whole-genome comparative analysis of gene sequence evolution in a non-mammalian vertebrate lineage. To analyze basic molecular evolutionary processes during avian evolution, and to contrast these with the situation in mammals, we aligned the protein-coding sequences of 8,384 1:1 orthologs of chicken, zebra finch, a lizard and three mammalian species.
Results: We found clear differences in the substitution rate at fourfold degenerate sites, being lowest in the ancestral bird lineage, intermediate in the chicken lineage and highest in the zebra finch lineage, possibly reflecting differences in generation time. We identified positively selected and/or rapidly evolving genes in avian lineages and found an overrepresentation of several functional classes, including anion transporter activity, calcium ion binding, cell adhesion and microtubule cytoskeleton.
Conclusions: Focusing specifically on genes of neurological interest and genes differentially expressed in the unique vocal control nuclei of the songbird brain, we find a number of positively selected genes, including synaptic receptors. We found no evidence that selection for beneficial alleles is more efficient in regions of high recombination; in fact, there was a weak yet significant negative correlation between ω and recombination rate, which is in the direction predicted by the Hill-Robertson effect if slightly deleterious mutations contribute to protein evolution. These findings set the stage for studies of functional genetics of avian genes.
Abstract: Population size estimates of waders, gulls and terns passing through or breeding in Central Asia are very scarce, although highly important for global flyway population estimates as well as for targeting local conservation efforts. The Tengiz-Korgalzhyn region is one of the largest wetland complexes in Central Asia. We conducted surveys in this region between 1999 and 2008 and present estimates of population size as well as information on phenology and age structure for 50
species of Charadriiformes. The Tengiz-Korgalzhyn wetlands are especially important for Red-necked Phalaropes Phalaropus lobatus and Ruffs Philomachus pugnax with, respectively, 41% and 13% of their flyway populations using the area during spring migration. The region is also an important post-breeding moulting site for Pied Avocets Recurvirostra avosetta and Black-tailed Godwits Limosa limosa used by, respectively, 5% and 4% of their flyway populations. Besides its key importance as a migratory stopover site, the study area is a key breeding site for the Critically Endangered Sociable Lapwing Vanellus gregarius, the Near Threatened Black-winged Pratincole Glareola nordmanni and for Pallas’s Gull Larus ichthyaetus with 16%, 6% and 5% of their world populations, respectively. We identified 29 individual sites that held more than 1% of the relevant flyway populations of at least one species of Charadriiformes. Including data on other species of waterbirds (mainly waterfowl), there were 93 sites that qualify for Important Bird Areas (IBA). About half of them are protected in a state nature reserve, while an additional 20% are recognised as IBAs. Nevertheless, 28 important sites are currently not recognised as IBAs nor are they protected by other conservation means. These sites require conservation attention.
Abstract: Repeatability (more precisely the common measure of repeatability, the intra-class correlation coefficient, ICC) is an important index for quantifying the accuracy of measurements and the constancy of phenotypes. It is the proportion of phenotypic variation that can be attributed to between-subject (or between-group) variation. As a consequence, the non-repeatable fraction of phenotypic variation is the sum of measurement error and phenotypic flexibility. There are several ways to estimate repeatability for Gaussian data, but there are no formal agreements on how repeatability should be calculated for non-Gaussian data (e.g. binary, proportion and count data). In addition to point estimates, appropriate uncertainty estimates (standard errors and confidence intervals) and statistical significance for repeatability estimates are required regardless of the types of data. We review the methods for calculating repeatability and the associated statistics for Gaussian and non-Gaussian data. For Gaussian data, we present three common approaches for estimating repeatability: correlation-based, analysis of variance (ANOVA)-based and linear mixed-effects model (LMM)-based methods, while for non-Gaussian data, we focus on generalised linear mixed-effects models (GLMM) that allow the estimation of repeatability on the original and on the underlying latent scale. We also address a number of methods for calculating standard errors, confidence intervals and statistical significance; the most accurate and recommended methods are parametric bootstrapping, randomisation tests and Bayesian approaches. We advocate the use of LMM- and GLMM-based approaches mainly because of the ease with which confounding variables can be controlled for. Furthermore, we compare two types of repeatability (ordinary repeatability and extrapolated repeatability) in relation to narrow-sense heritability. This review serves as a collection of guidelines and recommendations for biologists to calculate repeatability and heritability from both Gaussian and non-Gaussian data.
Abstract: Many species show substantial between-individual variation in mating preferences, but studying the causes of such variation remains a challenge. For example, the relative importance of heritable variation versus shared early environment effects (like sexual imprinting) on mating preferences has never been quantified in a population of animals. Here, we estimate the heritability of and early rearing effects on mate choice decisions in zebra finches based on the similarity of choices between pairs of genetic sisters raised apart and pairs of unrelated foster sisters. We found a low and nonsignificant heritability of preferences and no significant shared early rearing effects. A literature review shows that a low heritability of preferences is rather typical, whereas empirical tests for the relevance of sexual imprinting within populations are currently limited to very few studies. Although effects on preference functions (i.e., which male to prefer) were weak, we found strong individual consistency in choice behavior and part of this variation was heritable. It seems likely that variation in choice behavior (choosiness, responsiveness, sampling behavior) would produce patterns of nonrandom mating and this might be the more important source of between-individual differences in mating patterns.
Abstract: 1. Linear regression models are an important statistical tool in evolutionary and ecological studies. Unfortunately, these models often yield some uninterpretable estimates and hypothesis tests, especially when models contain interactions or polynomial terms. Furthermore, the standard errors for treatment groups, although often of interest for including in a publication, are not directly available in a standard linear model.
2. Centring and standardization of input variables are simple means to improve the interpretability of regression coefficients. Further, refitting the model with a slightly modified model structure allows extracting the appropriate standard errors for treatment groups directly fromthe model.
3. Centring will make main effects biologically interpretable even when involved in interactions and thus avoids the potential misinterpretation of main effects. This also applies to the estimation
of linear effects in the presence of polynomials. Categorical input variables can also be centred and this sometimes assists interpretation.
4. Standardization (z-transformation) of input variables results in the estimation of standardized slopes or standardized partial regression coefficients. Standardized slopes are comparable in magnitude
within models as well as between studies. They have some advantages over partial correlation coefficients and are often the more interesting standardized effect size.
5. The thoughtful removal of intercepts or main effects allows extracting treatment means or treatment slopes and their appropriate standard errors directly from a linear model. This provides a simple
alternative to the more complicated calculation of standard errors from contrasts and main effects.
6. The simple methods presented here put the focus on parameter estimation (point estimates as well as confidence intervals) rather than on significance thresholds. They allow fitting complex, but meaningful models that can be concisely presented and interpreted. The presented methods can also be applied to generalised linear models (GLM) and linear mixed models.
Notes: Evaluation at F1000 - http://f1000.com/12760956
Abstract: The developmental stress hypothesis offers a mechanism to maintain honesty of sexually selected ornaments, because only high quality individuals will be able to develop full ornamentation in the face of stress during early development. Experimental tests of this hypothesis have traditionally involved the manipulation of one aspect of the rearing conditions and an examination of effects on adult traits. Here, we instead use a statistically powerful quantitative genetic approach to detect condition dependence. We use animal models to estimate environmental correlations between a measure of early growth and adult traits. This way, we could make use of the sometimes dramatic differences in early growth of more than 800 individually cross-fostered birds and measure the effect on a total of 23 different traits after birds reached maturity. We find strong effects of environmental growth conditions on adult body size, body mass and fat deposition, moderate effects on beak colour in both sexes, but no effect on song and plumage characters. Rather surprisingly, there was no effect on male attractiveness, both measured in mate choice trials and under socially complex conditions in aviaries. There was a trend for a positive effect of good growth conditions on the success at fertilizing eggs in males breeding in aviaries whereas longevity was not affected in either sex. We conclude that zebra finches are remarkably resilient to food shortage during growth and can compensate for poor growth conditions without much apparent life-history trade-offs. Our results do not support the hypothesis that sexually selected traits show heightened condition dependence compared to nonsexually selected traits.
Abstract: Understanding the causes and consequences of variation in the rate of recombination is essential since this parameter is considered to affect levels of genetic variability, the efficacy of selection, and the design of association and linkage mapping studies. However, there is limited knowledge about the factors governing recombination rate variation. We genotyped 1920 single nucleotide polymorphisms in a multigeneration pedigree of more than 1000 zebra finches (Taeniopygia guttata) to develop a genetic linkage map, and then we used these map data together with the recently available draft genome sequence of the zebra finch to estimate recombination rates in 1 Mb intervals across the genome. The average zebra finch recombination rate (1.5 cM/Mb) is higher than in humans, but significantly lower than in chicken. The local rates of recombination in chicken and zebra finch were only weakly correlated, demonstrating evolutionary turnover of the
recombination landscape in birds. The distribution of recombination events was heavily biased toward ends of chromosomes, with a stronger telomere effect than so far seen in any organism. In fact, the recombination rate was as low as 0.1
cM/Mb in intervals up to 100 Mb long in the middle of the larger chromosomes. We found a positive correlation between recombination rate and GC content, as well as GC-rich sequence motifs. Levels of linkage disequilibrium (LD) were significantly
higher in regions of low recombination, showing that heterogeneity in recombination rates have left a footprint on the genomic landscape of LD in zebra finch populations.
Notes: Evaluation at F1000 - http://f1000.com/4258956
Abstract: Conspecific brood parasitism (CBP) brings the obvious fitness advantage of decreased breeding costs. However, the successful development of parasitic eggs depends on appropriate timing in relation to the host’s own eggs. A detailed documentation of CBP requires full knowledge of parentage.We achieved this in a captive population of zebra finches, Taeniopygia guttata, breeding in aviaries. The overall frequency of CBP was relatively high (21% of all host clutches, 5.4% of all eggs in host clutches) and comparable to what has been found in the wild in this species. A large proportion of paired females adopted a mixed strategy, laying one or two additional eggs in other nests before initiating their own clutches. Females showed a high individual consistency in whether they adopted a pure nonparasitic strategy or a mixed strategy, which is indicative of individual specialization. About 38% of all eggs laid outside a pair’s own nest were incubated by host pairs and can thus be considered successfully parasitic. No paired females were purely parasitic but unpaired females used CBP as a best of a bad job strategy. Hosts were targeted during the early phase of clutch initiation with the majority of parasitic eggs laid 0e5 days before the onset of incubation and usually before the host commenced egg laying. We did not find evidence that particular types of host females were targeted. The within-female repeatability of being a host was estimated to be negative. Overall, the systematic temporal patterns indicate targeted CBP behaviour in zebra finches.
Abstract: Recent developments in ecological statistics have reached behavioral ecology, and an increasing number of studies now apply analytical tools that incorporate alternatives to the conventional null hypothesis testing based on significance levels. However, these approaches continue to receive mixed support in our field. Because our statistical choices can influence research design and the interpretation of data, there is a compelling case for reaching consensus on statistical philosophy and practice.Here, we provide a brief overview of the recently proposed approaches and open an online forum for future discussion (https://bestat.ecoinformatics.org/). From the perspective of practicing behavioral ecologists relying on either correlative or experimental data, we review the most relevant features of information theoretic approaches,Bayesian inference, and effect size statistics. We also discuss concerns about data quality, missing data, and repeatability. We emphasize the necessity of moving away from a heavy reliance on statistical significance while focusing attention on biological relevance and effect sizes, with the recognition that uncertainty is an inherent feature of biological data. Furthermore, we point to the importance of integrating previous knowledge in the current analysis, for which novel approaches offer a variety of tools. We note, however, that the drawbacks and benefits of these approaches have yet to be carefully examined in association with behavioral data. Therefore, we encourage a philosophical change in the interpretation of statistical outcomes, whereas we still retain a pluralistic perspective for making objective statistical choices given the uncertainties around different approaches in behavioral ecology. We provide recommendations on how these concepts could be made apparent in the presentation of statistical outputs in scientific papers.
Abstract: The classical version of the differential allocation hypothesis states that, when females reproduce over their lifetime with partners that differ in their genetic quality, they should invest more in reproduction with highquality males. However, in species with lifetime monogamy, such as the zebra finch, partner quality will typically remain the same. In this case, the compensatory investment (CI) hypothesis predicts higher investment for low-quality males, because low genetic quality offspring are more dependent on maternal resources. Here, we show that female zebra finches invested more resources, both in terms of egg volume and yolk carotenoid content, when paired to a low genetic quality male, as judged from his previous ability to obtain extra-pair paternity in aviary colonies. We also found that females deposited slightly larger amounts of testosterone into eggs when paired to a low parental quality male, as judging from his previous success in rearing offspring. This is, to our knowledge, the first experimental support for the CI hypothesis in a species with lifetime monogamy. We stress that in more promiscuous species, the benefits of classical differential allocation may partly be neutralized by the supposed benefits of CI.
Abstract: Mixed-effect models are frequently used to control for the nonindependence of data points, for example, when repeated measures from the same individuals are available. The aim of these models is often to estimate fixed effects and to test their
significance. This is usually done by including random intercepts, that is, intercepts that are allowed to vary between individuals. The widespread belief is that this controls for all types of pseudoreplication within individuals. Here we show that this is not the case, if the aim is to estimate effects that vary within individuals and individuals differ in their response to these effects. In these cases, random intercept models give overconfident estimates leading to conclusions that are not supported by the data. By allowing individuals to differ in the slopes of their responses, it is possible to account for the nonindependence of data points that pseudoreplicate slope information. Such random slope models give appropriate standard errors and are easily implemented in standard statistical software. Because random slope models are not always used where they are essential, we suspect that many published findings have too narrow confidence intervals and a substantially inflated type I error rate. Besides reducing type I errors, random slope models have the potential to reduce residual variance by accounting for between-individual variation in slopes, which makes it easier to detect treatment effects that are applied between individuals, hence reducing type II errors as well.
Abstract: Range expansion linked to global warming is a widespread phenomenon among insects. This range expansion may be either gradual and on a broad-front or discontinuous following long distance dispersal. Many species of Orthoptera show a distinct wing-length dimorphism related to dispersal and rare long-wing individuals are assumed to contribute significantly to the colonisation of new habitat patches. Grid-based distribution surveys of Roesel's bush cricket Metriopera roeselii (Hagenbach 1822) at the edge of the species' range in NW' Germany were conducted in 1991, 1996 and 2004. Most newly colonised grid cells were directly adjacent to cells that were occupied in previous surveys or were connected to them by other colonised cells. The maximal distance between newly colonised grid cells and cells that were occupied in previous surveys was 6.3 km between 1991 and 1996 and 5.1 km between 1996 and 2004. The proportion of macropterous individuals sampled in 2004 was very low (1.4%). Macropterous individuals tended to occur in newly colonised, more isolated and low abundance grid cells. Hence, range expansion of M roeselii took place by short-distance colonisation from cells that were occupied in previous surveys rather than by single events of long-distance dispersal.
Abstract: Kin recognition abilities allow individuals to treat relatives differently. In mate choice contexts, kin recognition can ensure individuals avoid the costs of inbreeding. However, there is also the potential for assortative preferences for genetic similarity as part of an optimal outbreeding strategy. We tested the kin recognition abilities of captive female zebra finches, Taeniopygia guttata, in standard mate choice trials. A full individual cross-fostering scheme ensured that all subjects grew up in broods of only unrelated nestmates and were raised by unrelated foster parents. Therefore, individuals could use only self-referent phenotype matching (or recognition alleles), since exposure to genetic kin was excluded completely. Females were allowed the simultaneous choice between an unfamiliar genetic brother and unfamiliar, unrelated stimulus males. We used three cohorts of birds (199 females in total) that allowed three independent hypothesis tests. We found a significant avoidance of the unfamiliar brother in the first cohort, but could not replicate this finding in the other two cohorts. This was not easily explained by differences in the treatment of the cohorts, since the difference between cohorts was nonsignificant and testable differences in treatments did not show significant effects. The combined effect size was very low (d = -0.048) and nonsignificant. The initial finding of disassortative preferences may represent a type I error or there may be a true effect that is very weak and not easily reproducible. In any case, we did not find evidence of assortative preferences based on self-referent phenotype matching.
Abstract: Realistic population size estimates for waterbirds are crucial for the application of wetland conservation strategies, since the identification of internationally important wetlands is based on local numbers relative to the population size of the respective species. Central Asia is a poorly surveyed region that is situated at the intersection of migration routes that lead waterbirds from Western Siberia to the south-west (South-West Asia, East Africa) and to the south-east (South Asia, India). We calculated waterbird population estimates for the Tengiz–Korgalzhyn region, a large wetland complex in the steppe zone of Central Kazakhstan, based on waterbird surveys conducted between 1999 and 2004. For 20 of 43 species analysed the region supported more than 5% of the relevant flyway populations. Five species occurred with more than 40% of the flyway totals, including the Endangered White-headed Duck Oxyura leucocephala and the Vulnerable Dalmatian Pelican Pelecanus crispus. Peak numbers were recorded in summer and autumn and for most species numbers were more than an order of magnitude lower on spring migration compared with autumn migration. We identified 72 individual sites that held more than 20,000 waterbirds or more than 1% of a particular flyway population at least once. These sites are likely to constitute priorities for conservation. The general conservation status of the region is favourable, since many of the important sites are located within a strict nature reserve. However, outside the reserve hunting, fishing and powerline casualties represent conservation issues that should be monitored more carefully in the future.
Abstract: Sexual imprinting on discrete variation that serves the identification of species, morphs or sexes is well documented. By contrast, sexual imprinting on continuous variation leading to individual differences in mating preferences within a single species, morph and sex has been studied only once (in humans). We measured female preferences in a captive population of wildtype zebra finches. Individual cross-fostering ensured that all subjects grew up with unrelated foster parents and nest mates. Females from two cohorts (N = 113) were given a simultaneous choice between (two or four) unfamiliar males, one of which was a genetic son of their foster parents (SFP). We found no significant overall preference for the SFP (combined effect size d = 0.14 ± 0.15). Additionally, we tested if foster parent traits could potentially explain between-female variation in preferences. However, neither the effectiveness of cooperation between the parents nor male contribution to parental care affected female preferences for the son of the foster father. We conclude that at least in zebra finches sexual imprinting is not a major source of between-individual variation in mating preferences.
Abstract: To study the population genetics as well as the mating system of captive zebra finch (Taeniopygia guttata) populations, we developed primers for 12 microsatellite loci and screened them in 529 individuals from two successive generations of a single captive population. All markers were polymorphic with five to 14 alleles per locus. We checked all markers for Mendelian inheritance in 307 offspring whose parents were known for sure. Four markers showed evidence for the presence of null alleles. Once allowing for null alleles, we found no mismatches between offspring and parents, suggesting a very low rate of mutation. Average observed and expected heterozygosities across the eight loci showing no evidence for null-alleles was 0.819 and 0.812, respectively.
Abstract: Colourful ornaments are typically thought to be selected through female choice (intersexual selection), but often they also function as signals of dominance in intrasexual competition. The zebra finch, Taeniopygia guttata, is a well-studied model species for the evolution of colourful ornaments through female choice, and most research interest has focused on the red beak of males. However, results have been mixed, and in our population, we have found no female preference for males with redder beaks. To investigate whether beak colour is instead used as a signal in intrasexual competition, we studied aggressive behaviour of 160 male and 133 female zebra finches in experimentally staged encounters. Beak coloration was sexually dimorphic in the red and orange, as well as the ultraviolet (UV) part of the spectrum, where females showed a more pronounced UV peak. There was a trend for females with less male-like UV reflectance to be more aggressive, but otherwise, beak colour explained little, if any, of the variation in aggressiveness within sexes during competition for a potential partner. Hence beak colour is unlikely to be a signal of dominance, at least under our experimental conditions. Body size often influences the outcome of competition, and we found a weak but significant correlation between body size and aggressiveness that differed between the sexes. Large males were more aggressive than small males whereas small females were more aggressive than large females. Generally, the level of aggressiveness was highly repeatable within individuals, but beak colour and body size explained only little of the between-individual variation.
Abstract: The Sociable Lapwing Vanellus gregarius is a critically endangered species, probably declining from 5000 pairs to 500 pairs in 11 years. Fieldwork was conducted at two sites in Kazakhstan, May-August 2004, to identify causes of the species' decline. In total, 58 nests and a minimum of 36 broods in 16 colonies were found: colonies consisted of 1-8 nests that were on average 154 m apart, with 2.1 km between colonies. Although classified as biparental, the total proportion of time both parents spent incubating was low (77 +/- 2% se, n = 13 nests). Daily survival rates (Mayfield method) were very low during incubation (0.943 +/- 0.009 se) but high during the chick stage (0.986 +/- 0.004 se); incubation and chick-stage durations were found to be 28.5 and 29 days, respectively, so that the overall probability of any breeding attempt fledging chicks was 0.124 (0.055-0.274 95% confidence interval). A breeding attempt that produced fledglings, fledged 2.2 +/- 0.2 se chicks (n = 26) on average. Observed productivity predicted the population decline over the last 11 years well (using the maximum number of nesting attempts per pair of 1.4 that could have occurred in this study, and assuming an adult and first-year survival rate of 0.74 and 0.60, respectively, based on the means for Northern Lapwing Vanellus vanellus and Golden Plover Pluvialis apricalia). Nest survival during incubation (controlling for colony effects) may have been longer for nests in predominantly Artemisia rather than grass habitat. Mean nest survival for a colony was higher in areas with more bare ground and more nest predators, suggesting that predators were relatively unimportant in nest (egg or chick) mortality, but was lower in areas with high numbers of cattle, suggesting that trampling was important (64% of known-cause nest failures, n = 11, were trampled). Nests were preferentially sited in areas of Artemisia, where there was greater dung abundance, and probably shorter vegetation, suggesting that highly grazed vegetation is important for nesting. Chicks preferentially selected areas with a lower percentage of bare ground and possibly taller vegetation, suggesting that more vegetated areas are important for chicks. The results suggest that low egg survival due to nesting in areas of high grazer density may be responsible for the Sociable Lapwing's decline. Although grazers may create suitable vegetation for initial nesting, if those grazers remain at high density as in anthropogenic systems then they may reduce nest survival, probably through trampling. Experimentally maintaining grazing early but reducing it later in the breeding season is the logical first step in managing the species to increase egg survival and so to increase productivity.
Abstract: This paper presents recent data for the white-headed duck Oxyura leucocephala in the Tengiz-Korgalzhyn region, Central Kazakhstan. Most data were collected during surveys in the summer and autumn (July-October) 1999-2002. The region proved to hold significant numbers of the Central Asian population of white-headed duck in late summer/autumn. Numbers peak in September. It is estimated that 4 ,000-4,500 birds are present at t this time of the year. The size of the local breeding population is unknown. It is assumed that both the local population and birds from northern Kazakhstan and southern Siberia contribute to the autumn gatherings. Most autumn aggregations were found on lakes outside the Korgalzhynskij Nature Reserve (Zapovednik) while the reserve itself holds the main breeding sites. As it is essential to maintain numbers to ensure the survival of the Central Asian population, threats and conservation actions are discussed. The legal protection status seems favourable for the protection of the population. The main threats stem from water supply and management. Further problems include disturbance by hunters and fishermen.
Abstract: This paper summarises results of almost daily counts of Wood Sandpiper and an extensive ringing and colour-marking scheme at the sewage farm of Münster from 1969 to 2000. In the course of this 32-year period, migration phenology tended to have advanced in spring, and delayed in autumn. While roosting numbers remained stable in spring, they decreased in autumn, which is partly attributed to changes of the local habitat quality. A total of 1432 Wood Sandpipers were ringed and measured. Analysis of biometric data revealed larger wing and tail length in juveniles due to feather wear in adults, whereas bill and nalospi were longer in adult birds. In spring, birds had longer wings and tails, but lower body mass than adults caught in autumn. While birds with active primary moult have so far hardly been reported from other sites in Central Europe, our data indicate that a low number of birds regularly start moult of remiges at an early stage of autumn migration. Recoveries indicate that birds passing through Münster take a more south-westerly route than generally assumed for Central European migrants. A bird ringed at Münster is to our knowledge the oldest known individual of the species (at least 11-years-old).
Abstract: In 1991, a pair of Two-barred Crossbills bred successfully on a cemetery of Berlin, which is the first certain breeding record in Central Europe of this species. Two young fledged May 29. The tree stand of the cemetery consists of 80 % deciduous trees and 20 % conifers only, which means the selection of an open, mixed deciduous forest type. This event has to be seen in connection with a very intense invasion of Crossbills to Central and Western Europe. Some notes are given on plumage characters, behaviour and vocalizations.
