Population Of Great Tits Research Articles

How many insects can a great tit population prey on in apple organic orchards? A modelling bioenergetics study

Orchards represent relevant study systems for investigating the functional role of insectivorous birds as regulators of pest insect populations. In this context, we used a bioenergetics model (Wiens and Innis, 1974) to estimate the seasonal variation in daily insect consumption by natural populations of the great tit (Parus major) in organic apple orchards. This model allowed us to estimate the changes in both adult densities and energy requirements in a P. major population, using field-measured parameters such as the brood size, and the length of incubation. The calculation of insect consumption rate by birds was based on both the existing literature on great tit diets and the simulated energy requirement of a great tit population. The effect of a temperature increase on energy requirement has been quantified. This study opens the way to consider the functional role of birds in agricultural landscapes and how this role may translate to ecosystem services.

Eggshell speckling in a passerine bird reveals chronic long-term decline in soil calcium

ABSTRACTCapsule: Long-term changes in eggshell speckling correlated temporally and spatially with declining soil calcium in an English Great Tit Parus major population.Aims: Eggshell speckling in the Great Tit correlates with eggshell thickness and calcium availability. We investigated whether eggshell speckling changed in a Great Tit population during a period when soil calcium declined, and estimated changes in eggshell thickness.Methods: Eggshell pigmentation of 2313 Great Tit clutches was recorded in 1988–2007 across a geological gradient in Wytham Woods, UK. Soil surveys conducted in 1974 and 1991 were repeated in 2008. Temporal and spatial changes in eggshell speckling and soil calcium were examined using generalized linear mixed models. We also estimated the change in eggshell thickness over this period.Results: Soil-calcium availability declined 1974–2008 especially in calcium-rich limestone areas. A systematic change in eggshell speckling, approximating to a 6.5% reduction in eggshell thickness, occurred between 1988 and 2007. The change was greatest in parts of Wytham that experienced the greatest decline in soil calcium. Hatching success was unaffected.Conclusion: Soil-calcium availability has declined in Wytham Woods, affecting Great Tit eggshell characteristics. This is the first evidence that declining soil calcium affects birds nesting in calcium-rich areas. Practical applications of these findings are considered.

Multi-Element Analysis of Blood Samples in a Passerine Species: Excesses and Deficiencies of Trace Elements in an Urbanization Study

Urbanization is a growing phenomenon characterized by a complete restructuring of natural areas. In urban bird populations, a reduced offspring survival and body condition and an overall lower breeding success are often observed compared to populations inhabiting more natural habitats. Higher pollution levels and poorer quality of natural resources in cities are two environmental factors frequently mentioned in the literature to explain the differences between urban and non-urban populations. Pollution and poor quality of food may lead to an excess of non-essential elements such as Pb or Cd or to deficiencies of essential elements such as Cu or Zn, which may explain some of the impacts, notably on immunity, observed in urbanization studies. The present study compared the breeding parameters, brood body mass and condition, and haptoglobin levels, a marker of inflammatory immunity, in two urban and two forest populations of Great tits in Eastern France, together with a multi-element analysis (25 non-essential and essential trace elements) of blood samples from 13-day-old nestlings from the four populations. The concentration of NO2, a gaseous pollutant typical of urban pollution, was also measured. The NO2 concentrations were significantly higher in the urban areas, but no association with biological variables was detected. Non-essential metals were undetectable in the plasma of the birds from both habitats, except Pb, whose concentrations, however, did not differ between the urban and forest birds. A positive relationship was found between the plasmatic richness in essential elements (as assessed from the coordinates of the first axis of a PCA including 12 elements) and the average brood body mass and condition. We suggest that lower quality resources or/and a higher metabolic demand may be a causal mechanism for the reduced body condition often observed in urban bird nestlings. Finally, our exploratory study could promote more mechanistic experiments (e.g. supplementation) to explain the negative effect of urban conditions on bird populations.

Hatching asynchrony vs. foraging efficiency: the response to food availability in specialist vs. generalist tit species.

Breeding mistiming is increasingly frequent in several ecosystems in the face of current climate change. Species belonging to higher trophic levels must employ mechanisms to reduce it. One of these mechanisms is hatching asynchrony, with the eggs in a clutch hatching over a period of several days. Some authors have suggested it to be adaptive when food is unpredictable. However, these birds can also suffer associated costs. We tested whether a species with higher foraging efficiency avoid hatching asynchrony compared to its sister species. We studied hatching asynchrony and nestling provisioning in relation to food availability in sympatric populations of blue and great tits. For the first time, we show that sister species respond to food availability with different strategies. Blue tit feeding rates readily responded to the abundance of their main prey, and also reduced the impact of nestling size hierarchy on mean nestling weight, consequently increasing fledging rate. Our results suggest that levels of hatching asynchrony seem to be influenced by species-specific life history traits, as generalist foragers rely less on it. They also highlight the importance of multi-species approaches when studying the response of organisms to environmental unpredictability.

Effect of an anti-malaria drug on behavioural performance on a problem-solving task: An experiment in wild great tits

Malaria parasites have been shown to decrease host fitness in several species in the wild and their detrimental effects on host cognitive ability are well established in humans. However, experimental demonstrations of detrimental effects on non-human host behaviour are currently limited. In this study, we experimentally tested whether injections of an anti-malaria drug affected short-term behavioural responses to a problem-solving task during breeding in a wild population of great tits (Parus major) naturally infected with malaria. Adult females treated against malaria were more active than control females, even though they were not more likely to solve the task or learn how to do so, suggesting that energetic constraints could shape differences in some behaviours while changes in cognitive performances might require more time for the neural system to recover or may depend mainly on infection at the developmental stage. Alternatively, parasite load might be a consequence, rather than a cause, of inter-individual variation in cognitive performance. These results also suggest that inter-individual as well as inter-population differences in some behavioural traits may be linked to blood parasite load.

Nestling Growth is Impaired by Heat Stress: an Experimental Study in a Mediterranean Great Tit Population.

Samuel Rodríguez and Emilio Barba (2016) During the nestling stage, nestlings of small altricial birds face energetic limitations due to their rapid development and the need to maintain a stable body temperature once homeothermy is achieved. In Mediterranean habitats, high air temperatures reached during the breeding season could negatively affect the health and condition of the nestlings. The aim of this study was to determine the effect of an experimental increase of nest temperatures during the nestling stage on the growth and survival of Great Tit (Parus major) nestlings. Additionally, changes in parental brooding and feeding behavior as a result of the alteration of the nest microclimate were addressed. Increased nest temperatures affected nestling mass, as heated nestlings were lighter than controls on day 15 in the warmer of the two breeding seasons considered. Moreover, females from the heating treatment reduced their brooding time. Fledging success and parental feeding rates were not altered by the experimental treatment. The results of this study suggest that high nest temperatures may impair nestling development and therefore affect post-fledging survival probability. Negative effects are more likely to occur in warm habitats and/or warmer years, where juveniles are liable to suffer from thermal stress.

Relationship between Blood Haemoglobin and Glucose Concentrations in Adult Great Tits (Parus Major) and Blue Tits (Cyanistes Caeruleus)

Haematological and blood chemistry variables are widely used in ecophysiological research as physiological indices of body condition in various vertebrate taxa. In this study, we analysed relationships between blood glucose and blood haemoglobin concentrations of adult birds in wild populations of Blue Tits ( Cyanistes caeruleus) and Great Tits ( Parus major) during the breeding season in central Poland. We found that blood glucose and blood haemoglobin concentrations are negatively correlated. We also show that individual Blue Tits have higher mean haemoglobin levels adjusted for the common value of glucose concentration than individual Great Tits and that females of both species have higher mean haemoglobin concentrations than males. Our results suggest that haematological as well as biochemical variables may be used in tune as complementary indices of body condition in wild bird populations.

Density dependence in an age-structured population of great tits: identifying the critical age classes.

Classical approaches for the analyses of density dependence assume that all the individuals in a population equally respond and equally contribute to density dependence. However, in age-structured populations, individuals of different ages may differ in their responses to changes in population size and how they contribute to density dependence affecting the growth rate of the whole population. Here we apply the concept of critical age classes, i.e., a specific scalar function that describes how one or a combination of several age classes affect the demographic rates negatively, in order to examine how total density dependence acting on the population growth rate depends on the age-specific population sizes. In a 38-yr dataset of an age-structured great tit (Parus major) population, we find that the age classes, including the youngest breeding females, were the critical age classes for density regulation. These age classes correspond to new breeders that attempt to take a territory and that have the strongest competitive effect on other breeding females. They strongly affected population growth rate and reduced recruitment and survival rates of all breeding females. We also show that depending on their age class, females may differently respond to varying density. In particular, the negative effect of the number of breeding females was stronger on recruitment rate of the youngest breeding females. These findings question the classical assumptions that all the individuals of a population can be treated as having an equal contribution to density regulation and that the effect of the number of individuals is age independent. Our results improve our understanding of density regulation in natural populations.

Genetic variation in variability: Phenotypic variability of fledging weight and its evolution in a songbird population.

Variation in traits is essential for natural selection to operate and genetic and environmental effects can contribute to this phenotypic variation. From domesticated populations, we know that families can differ in their level of within-family variance, which leads to the intriguing situation that within-family variance can be heritable. For offspring traits, such as birth weight, this implies that within-family variance in traits can vary among families and can thus be shaped by natural selection. Empirical evidence for this in wild populations is however lacking. We investigated whether within-family variance in fledging weight is heritable in a wild great tit (Parus major) population and whether these differences are associated with fitness. We found significant evidence for genetic variance in within-family variance. The genetic coefficient of variation (GCV) was 0.18 and 0.25, when considering fledging weight a parental or offspring trait, respectively. We found a significant quadratic relationship between within-family variance and fitness: families with low or high within-family variance had lower fitness than families with intermediate within-family variance. Our results show that within-family variance can respond to selection and provides evidence for stabilizing selection on within-family variance.

More daughters in a less favourable world: Breeding in intensively-managed orchards affects tertiary sex-ratio in the great tit

Offspring sex-ratio is a key life-history trait that shows considerable variation among many bird species. Habitat quality is one of the numerous environmental factors acting on bias in sex-ratios in passerines. For the great tit Parus major, southern French apple orchards constitute both feeding and breeding habitats of considerably varying quality depending on the annual amount of chemical pesticides used for pest control, which have both direct (toxicity) and indirect (lower prey availability) effects on bird populations. In a two-year study, we specifically assessed the effect of three pest management strategies involving high (conventional), moderate (IPM) and no (organic) chemical pesticide inputs on fledgling sex-ratio using molecular sexing techniques. We found that great tit populations had significant variations in fledgling sex-ratio across our range of habitat quality, with conventional apple orchards producing a more biased sex-ratio towards daughters than IPM and organic orchards. Estimates of maternal traits (female body condition, first egg-laying date, clutch size and hatching rate) were also analysed but they were not significant predictors of brood sex-ratio. This study supports the sensitivity of bird tertiary sex-ratio to habitat quality. It also suggests that highly pesticide-treated agro-ecosystems may be poorer habitats for temperate insectivorous bird species. We provide further evidence that reducing chemical pressure might mitigate anthropogenic impacts on bird life-histories and population dynamics.

Multivariate selection and intersexual genetic constraints in a wild bird population.

When selection differs between the sexes for traits that are genetically correlated between the sexes, there is potential for the effect of selection in one sex to be altered by indirect selection in the other sex, a situation commonly referred to as intralocus sexual conflict (ISC). While potentially common, ISC has rarely been studied in wild populations. Here, we studied ISC over a set of morphological traits (wing length, tarsus length, bill depth and bill length) in a wild population of great tits (Parus major) from Wytham Woods, UK. Specifically, we quantified the microevolutionary impacts of ISC by combining intra- and intersex additive genetic (co)variances and sex-specific selection estimates in a multivariate framework. Large genetic correlations between homologous male and female traits combined with evidence for sex-specific multivariate survival selection suggested that ISC could play an appreciable role in the evolution of this population. Together, multivariate sex-specific selection and additive genetic (co)variance for the traits considered accounted for additive genetic variance in fitness that was uncorrelated between the sexes (cross-sex genetic correlation=-0.003, 95% CI=-0.83, 0.83). Gender load, defined as the reduction in a population's rate of adaptation due to sex-specific effects, was estimated at 50% (95% CI=13%, 86%). This study provides novel insights into the evolution of sexual dimorphism in wild populations and illustrates how quantitative genetics and selection analyses can be combined in a multivariate framework to quantify the microevolutionary impacts of ISC.

Habitat structure influences the song characteristics within a population of Great Tits Parus major

ABSTRACTCapsule: The structure of Great Tit Parus major songs is shaped by the acoustic properties of the habitat within the breeding territory of individuals.Aim: To test whether the structure of the habitat influences song structure within a population of Great Tits P. major.Methods: We recorded Great Tit songs from 42 territories on two different days and measured the habitat structure in each territory. We also trapped the males and estimated the breeding density around each territory, so were able to control the analysis by date, breeding density and male characteristics.Results: Song pause length was positively affected by the ground cover, while the song rate and the minimum frequency were negatively affected by the shrub cover. Male size negatively affected the peak frequency of the songs, whereas the age of the males affected the frequency range; older males sang with a broader bandwidth.Conclusion: This study suggests that Great Tits are capable of adjusting their vocalizations in each territory, presumably to enhance transmission owing to vocal plasticity.

Great tits trade off future competitive advantage for current reproduction

Quantifying the fitness costs of reproduction is essential to understand the evolution of reproductive behavior. Recent work shows that increased reproductive investment reduced parental survival in more competitive environments. Here we experimentally test the hypothesis that reproductive investment has a negative effect on the ability of parents to compete for resources in later life. In a nest-box population of Great tits (Parus major), we manipulated family size by reducing or enlarging broods with 2 or 3 nestlings, relative to a control group, in 2 years (N = 237 broods). Parental feeding effort was positively related to experimental family size but leveled off for the enlarged broods. In the next breeding season we manipulated the nest box quality in early spring by reducing the depth of 80% of the nest boxes (deeper boxes are safer and preferred). We analyzed parents' probability of obtaining a deep breeding box in relation to their previous year's family size manipulation. We found for both years that increased reproductive investment negatively affected the probability of parents to claim a high-quality nest box in the subsequent breeding season. We thus confirm that family size has a negative effect on the future competitive ability of parents. Such carry-over effects are important because they show that selection on individual optimal clutch size will depend on 1) resource abundance and the level of competition in the next breeding season and 2) the reproductive investment of the competitors in the current breeding season because it affects their future competitive ability as well.

The evolution of labile traits in sex- and age-structured populations.

Summary Many quantitative traits are labile (e.g. somatic growth rate, reproductive timing and investment), varying over the life cycle as a result of behavioural adaptation, developmental processes and plastic responses to the environment. At the population level, selection can alter the distribution of such traits across age classes and among generations. Despite a growing body of theoretical research exploring the evolutionary dynamics of labile traits, a data‐driven framework for incorporating such traits into demographic models has not yet been developed.Integral projection models (IPMs) are increasingly being used to understand the interplay between changes in labile characters, life histories and population dynamics. One limitation of the IPM approach is that it relies on phenotypic associations between parents and offspring traits to capture inheritance. However, it is well‐established that many different processes may drive these associations, and currently, no clear consensus has emerged on how to model micro‐evolutionary dynamics in an IPM framework.We show how to embed quantitative genetic models of inheritance of labile traits into age‐structured, two‐sex models that resemble standard IPMs. Commonly used statistical tools such as GLMs and their mixed model counterparts can then be used for model parameterization. We illustrate the methodology through development of a simple model of egg‐laying date evolution, parameterized using data from a population of Great tits (Parus major).We demonstrate how our framework can be used to project the joint dynamics of species' traits and population density. We then develop a simple extension of the age‐structured Price equation (ASPE) for two‐sex populations, and apply this to examine the age‐specific contributions of different processes to change in the mean phenotype and breeding value.The data‐driven framework we outline here has the potential to facilitate greater insight into the nature of selection and its consequences in settings where focal traits vary over the lifetime through ontogeny, behavioural adaptation and phenotypic plasticity, as well as providing a potential bridge between theoretical and empirical studies of labile trait variation.

Wherever I may roam: social viscosity and kin affiliation in a wild population despite natal dispersal.

Dispersal affects the social contexts individuals experience by redistributing individuals in space, and the nature of social interactions can have important fitness consequences. During the vagrancy stage of natal dispersal, after an individual has left its natal site and before it has settled to breed, social affiliations might be predicted by opportunities to associate (e.g., distance in space and time between natal points of origin) or kin preferences. We investigated the social structure of a population of juvenile great tits (Parus major) and asked whether social affiliations during vagrancy were predicted by 1) the distance between natal nest-boxes, 2) synchrony in fledge dates, and 3) accounting for spatial and temporal predictors, whether siblings tended to stay together. We show that association strength was affected predominantly by spatial proximity at fledging and, to a lesser extent, temporal proximity in birth dates. Independently of spatial and temporal effects, sibling pairs associated more often than expected by chance. Our results suggest that the structure of the winter population is shaped primarily by limits to dispersal through incomplete population mixing. In addition, our results reveal kin structure, and hence the scope for fitness-related interactions between particular classes of kin. Both spatial-mediated and socially mediated population structuring can have implications for our understanding of the evolution of sociality.

To sing or not to sing: seasonal changes in singing vary with personality in wild great tits

Expression of sexually selected signals in many species varies over time of day and season. A key model system to study this variation in signal expression is birdsong. Yet, despite good ecological understanding of why song varies across time of day and season, much of the individual variation remains unexplained. Although some of the interindividual variation in singing depends on the quality or motivation of an individual, it can also vary with other characteristics. Because singing has been shown to vary with personality traits in specific contexts, personality is thus an important candidate to explain part of the variation in seasonal and daily singing. Using a personality-typed field population of great tits (Parus major), we here show that singing activity peaked at dawn during the fertile period of the females and that the association between male personality and singing activity depended on the reproductive stage of his mate; faster explorers significantly increased in singing activity during main periods of fertility and maternal investment (egg laying and incubation). Moreover, males with higher singing activity tended to raise more fledglings. Increased singing by faster explorers during key periods of female reproductive investment suggests that faster explorers are more responsive to changes in female reproductive stage, contrasting the general view that faster explorers are less responsive to environmental and social changes. Most importantly, these findings highlight that multiple factors including personality need to be integrated when assessing causes of variation of highly variable sexually selected signal traits.

Behavioral and morphological responses to perceived predation risk: a field experiment in passerines

Predators can affect prey both directly (consumptive effects) and indirectly (nonconsumptive effects), with a growing body of literature showing the latter may have pronounced effects. Prey populations are comprised of individuals that differ in perception of and willingness to take risk; therefore, studying how different types of individuals respond to predation risk is necessary to fully understand prey dynamics. Playbacks were used to experimentally manipulate perceived predation risk in nest-box populations of wild great tits (Parus major) to examine the nonconsumptive effects of avian predators on prey behavior and morphology, and to explore individual differences in prey response. Individuals responded to our treatment, and responses differed depending on both treatment and premanipulation behavioral type. Birds in areas exposed to predator playback tended to decrease in body mass more than birds exposed to nonthreatening (control) playback. Differences between treatment groups were mainly driven by initially fast exploring birds: In the control treatment, fast explorers increased in mass, whereas the initially fast exploring birds in the predation treatment decreased in mass. Furthermore, birds exposed to predator playback decreased exploratory tendency compared with controls. These findings demonstrate that predation risk alters great tit behavior (exploration) and morphology (body mass) and that plasticity in response to risk relates to an individual’s willingness to take risks. Our findings suggest that individuals differ in susceptibility to predation risk, causing adaptive individual differences in responsiveness to changes in predation risk. Acknowledging individuality in responses to perceived predation risk has important consequences for understanding prey dynamics.

Replicated analysis of the genetic architecture of quantitative traits in two wild great tit populations.

Currently, there is much debate on the genetic architecture of quantitative traits in wild populations. Is trait variation influenced by many genes of small effect or by a few genes of major effect? Where is additive genetic variation located in the genome? Do the same loci cause similar phenotypic variation in different populations? Great tits (Parus major) have been studied extensively in long‐term studies across Europe and consequently are considered an ecological ‘model organism’. Recently, genomic resources have been developed for the great tit, including a custom SNP chip and genetic linkage map. In this study, we used a suite of approaches to investigate the genetic architecture of eight quantitative traits in two long‐term study populations of great tits—one in the Netherlands and the other in the United Kingdom. Overall, we found little evidence for the presence of genes of large effects in either population. Instead, traits appeared to be influenced by many genes of small effect, with conservative estimates of the number of contributing loci ranging from 31 to 310. Despite concordance between population‐specific heritabilities, we found no evidence for the presence of loci having similar effects in both populations. While population‐specific genetic architectures are possible, an undetected shared architecture cannot be rejected because of limited power to map loci of small and moderate effects. This study is one of few examples of genetic architecture analysis in replicated wild populations and highlights some of the challenges and limitations researchers will face when attempting similar molecular quantitative genetic studies in free‐living populations.

Timing of extrapair fertilizations: within-pair fertilization trade-offs or pair synchrony spillovers?

In socially monogamous species, male fertilization-related behaviors are expected to be tuned to the fertile cycle of their social female. How a male adjusts his fertilization-related behaviors to his social mate's fertile period is relatively well understood. However, the influence of the social mate's fertility stage on a male's extrapair siring success remains poorly studied. In this study, we tested 2 alternative hypotheses about how a male's extrapair siring success may vary in relation to his social mate's fertile cycle. The tradeoff avoidance hypothesis posits that males engage in extrapair fertilization-related behaviors when their social female is not fertile to avoid a potential trade-off between within-pair and extrapair reproduction. Alternatively, the pair synchrony hypothesis postulates that males are more likely to sire extrapair offspring when their social mate is fertile because male investment in fertilization- related behaviors during their social mate's fertile period aimed at increasing within-pair siring success will have positive spillover effects on their extrapair siring success. To assess the support for each of these 2 hypotheses, we studied a population of great tits (Parus major) for 4 consecutive years in 12 nest-box plots and quantified each male's extrapair siring success before, during, and after the fertile period of his social mate. After correcting for variation in the availability of fertile females, males gained more extrapair paternity during the fertile period of their social mate, supporting the pair synchrony hypothesis.

Genetic responses to seasonal variation in altitudinal stress: whole-genome resequencing of great tit in eastern Himalayas.

Species that undertake altitudinal migrations are exposed to a considerable seasonal variation in oxygen levels and temperature. How they cope with this was studied in a population of great tit (Parus major) that breeds at high elevations and winters at lower elevations in the eastern Himalayas. Comparison of population genomics of high altitudinal great tits and those living in lowlands revealed an accelerated genetic selection for carbohydrate energy metabolism (amino sugar, nucleotide sugar metabolism and insulin signaling pathways) and hypoxia response (PI3K-akt, mTOR and MAPK signaling pathways) in the high altitudinal population. The PI3K-akt, mTOR and MAPK pathways modulate the hypoxia-inducible factors, HIF-1α and VEGF protein expression thus indirectly regulate hypoxia induced angiogenesis, erythropoiesis and vasodilatation. The strategies observed in high altitudinal great tits differ from those described in a closely related species on the Tibetan Plateau, the sedentary ground tit (Parus humilis). This species has enhanced selection in lipid-specific metabolic pathways and hypoxia-inducible factor pathway (HIF-1). Comparative population genomics also revealed selection for larger body size in high altitudinal great tits.