Haematozoa infections in a Great Tit Parus major population in Central Portugal: relationships with breeding effort and health

Blood parasites may act as modulators of their hosts' ecology, life histories and fitness. We studied the prevalence of Plasmodium sp., Haemoproteus sp. and Leucocytozoon sp. and their effects on morphological, biochemical and haematological variables and on breeding effort of Great Tits Parus major . Total prevalence (percentage of individuals infected by any parasite) ranged from 7.7% to 61.1%. There was an overall positive association in prevalence between the three haematozoan parasites. No effect of sex or age on infection status was observed. Negative impacts of infection on physiological condition depended largely on year and/or season and included effects on body condition index, plasma protein and haemoglobin index. There were also indications that parasite infection increased immune response and stress levels and activated antioxidant defence mechanisms. Males with higher fledging success had a higher probability of Haemoproteus infection, and females laying heavier eggs had a higher probability of Plasmodium infection. However, clutch size was negatively associated with the probability of infection by Leucocytozoon and Haemoproteus . Surprisingly, males raising second broods had a lower prevalence of both Haemoproteus and Leucocytozoon . Only 5.7% of first-brood nestlings were infected, but those in infected nestboxes had a lower heterophil/lymphocyte ratio. This study confirms the pathogenicity of blood parasites to the host by demonstrating negative effects of infection on both physiology and breeding performance.     

Early morning fledging improves recruitment in Great Tits Parus major

A potential key event linking the nestling phase to first‐year survival is fledging (nest leaving) because this process is characterized by a major change of environments and therefore a sudden shift in selective forces. Here we assessed whether different facets of fledging predicted subsequent survival (measured as local recruitment) in Great Tits Parus major. Nestlings had a higher recruitment probability when they fledged early in the morning and when they were heavy. The existence of selection for fledging early in the day has been suggested before, but here we provide the first empirical evidence in support of that prediction.     

Individual variation in feather corticosterone levels and its influence on haemosporidian infection in a Neotropical bird

Corticosterone (CORT) is the main glucocorticoid hormone of amphibians, reptiles, birds and some mammals. This hormone may have evolved as an adaptive metabolic mechanism, in part because increased concentrations of CORT are essential for individuals to manage energy resources and thus cope with negative perturbations such as predation and storms. The benefits of CORT are offset by costs, because elevated levels can suppress inflammatory responses of individuals, making them more susceptible to parasites and pathogens. In this study, we investigated the relationships between feather CORT levels, infection status and diversity of haemosporidian parasites in the Blue-crowned Manakin Lepidothrix coronata, considering possible effects related to the sex and age of individuals. We predicted higher levels of feather CORT in infected individuals. We observed that feather CORT levels were similar among individuals of different sexes and ages. Although haemosporidian infection status did not vary among sexes, occurrence probability was higher among younger individuals, which may indicate that the less developed immune system of these individuals makes them more susceptible to avian malaria. Contrary to expectations, we found that feather CORT levels were not associated with the infection status and diversity of haemosporidian parasites. That haemosporidian occurrence probability does not increase with elevated feather CORT levels suggests that individuals are not immunosuppressed by elevated levels of this hormone, at least to the extent that feather CORT truly reflects individual differences in the level of this hormone.     

Determinants of haemosporidian single- and co-infection risks in western palearctic birds

Understanding the drivers of infection risk helps us to detect the most at-risk species in a community and identify species whose intrinsic characteristics could act as potential reservoirs of pathogens. This knowledge is crucial if we are to predict the emergence and evolution of infectious diseases. To date, most studies have only focused on infections caused by a single parasite, leaving out co-infections. Yet, co-infections are of paramount importance in understanding the ecology and evolution of host-parasite interactions due to the wide range of effects they can have on host fitness and on the evolutionary trajectories of parasites. Here, we used a multinomial Bayesian phylogenetic modelling framework to explore the extent to which bird ecology and phylogeny impact the probability of being infected by one genus (hereafter single infection) or by multiple genera (hereafter co-infection) of haemosporidian parasites. We show that while nesting and migration behaviours influenced both the probability of being single- and co-infected, species position along the slow-fast life-history continuum and geographic range size were only pertinent in explaining variation in co-infection risk. We also found evidence for a phylogenetic conservatism regarding both single- and co-infections, indicating that phylogenetically related bird species tend to have similar infection patterns. This phylogenetic signal was four times stronger for co-infections than for single infections, suggesting that co-infections may act as a stronger selective pressure than single infections. Overall, our study underscores the combined influence of hosts’ evolutionary history and attributes in determining infection risk in avian host communities. These results also suggest that co-infection risk might be under stronger deterministic control than single infection risk, potentially paving the way toward a better understanding of the emergence and evolution of infectious diseases.     

Environmental drivers of roosting body mass variation in boreal Great Tits Parus major

Small wintering passerines adaptively modulate daily body mass acquisition as part of their energy management policy. However, whether birds optimize overnight mass loss or body mass at dawn remains poorly understood. We studied environmental correlates of individual variation in body mass at dusk, overnight mass loss and body mass at dawn in a wild population of Great Tits Parus major wintering in northern Fennoscandia. Body mass at dusk, overnight mass loss and body mass at dawn were independent of prevailing conditions despite extremely low night ambient temperatures. Body mass at dusk was higher in males than in females, and decreased throughout winter and when snowfall was higher in the previous month. Overnight mass loss increased with precipitation during the previous week and tended to be higher in mid‐winter, when nights were longest. However, birds reduced overnight mass loss with higher temperatures in the previous week and higher precipitation in the previous 2 weeks. Dawn body mass was strongly correlated with dusk body mass and overnight mass loss, and showed only mild associations with weather variables once dusk mass was accounted for. Body mass in roosting boreal Great Tits seems to be constrained by recent snowfall as the winter progresses, but otherwise appears to be mostly unaffected by previous and current temperatures, suggesting a regular use of facultative hypothermia.     

The effect of old age on the reproduction of Great Tits Parus major and Blue Tits P. caeruleus

The results from two data sets show that in Great Tits Parus major and Blue Tits P. caeruleus reproduction is influenced by age. In both species, laying dates become earlier while clutch- and brood-size increase between the ages of 1 and 2, but there is no change in nesting success or post-fledging juvenile survival. Great Tits aged 5 or older are 'old' in that laying starts later and nesting success, brood-size and post-fledging juvenile survival decrease. Blue Tits become 'old' 1 year earlier than Great Tits: females aged 4 or older lay later, have a lower nesting success and smaller brood-size, and their young show a decreased post-fledging survival. The effect on laying date, in the Blue Tit, becomes apparent only for females aged 6 and older. It is concluded that ageing in small passerines is to be expected more generally, but that no extrapolations can be made as to the timing of the effect from one species to another.     

Endocrine phenotype,reproductive success and survival in the great tit,Parus major

A central goal in evolutionary ecology is to characterize and identify selection patterns on the optimal phenotype in different environments. Physiological traits, such as hormonal responses, provide important mechanisms by which individuals can adapt to fluctuating environmental conditions. It is therefore expected that selection shapes hormonal traits, but the strength and the direction of selection on plastic hormonal signals are still under investigation. Here, we determined whether, and in which way, selection is acting on the hormones corticosterone and prolactin by characterizing endocrine phenotypes and their relationship with fitness in free‐living great tits, Parus major. We quantified variation in circulating concentrations of baseline and stress‐induced corticosterone and in prolactin during the prebreeding (March) and the breeding season (May) for two consecutive years, and correlated these with reproductive success (yearly fledgling number) and overwinter survival in female and male individuals. In both years, individuals with high baseline corticosterone concentrations in March had the highest yearly fledgling numbers; while in May, individuals with low baseline corticosterone had the highest yearly reproductive success. Likewise, individuals that displayed strong seasonal plasticity in baseline corticosterone concentrations (high in March and low in May) had the highest reproductive success in each year. Prolactin concentrations were not related to reproductive success, but were positively correlated to the proximity to lay. Between‐year plasticity in stress‐induced corticosterone concentrations of males was related to yearly variation in food abundance, but not to overall reproductive success. These findings suggest that seasonally alternating directional selection is operating on baseline corticosterone concentrations in both sexes. The observed between‐year consistency in selection patterns indicates that a one‐time hormone sample in a given season can allow the prediction of individual fitness.     

Ontogenetic timing as a condition‐dependent life history trait: High‐condition males develop quickly,peak early,and age fast

Within‐population variation in ageing remains poorly understood. In males, condition‐dependent investment in secondary sexual traits may incur costs that limit ability to invest in somatic maintenance. Moreover, males often express morphological and behavioral secondary sexual traits simultaneously, but the relative effects on ageing of investment in these traits remain unclear. We investigated the condition dependence of male life history in the neriid fly Telostylinus angusticollis. Using a fully factorial design, we manipulated male early‐life condition by varying nutrient content of the larval diet and, subsequently, manipulated opportunity for adult males to interact with rival males. We found that high‐condition males developed more quickly and reached their reproductive peak earlier in life, but also experienced faster reproductive ageing and died sooner than low‐condition males. By contrast, interactions with rival males reduced male lifespan but did not affect male reproductive ageing. High‐condition in early life is therefore associated with rapid ageing in T. angusticollis males, even in the absence of damaging male–male interactions. Our results show that abundant resources during the juvenile phase are used to expedite growth and development and enhance early‐life reproductive performance at the expense of late‐life performance and survival, demonstrating a clear link between male condition and ageing.     

Host ecology and life-history traits associated with blood parasite species richness in birds

Identifying host traits associated with the number of different parasite species or strains harboured by a particular host species can have important implications for understanding the impact of parasitism on hosts. We investigated associations between host ecology and life history, and parasite richness and prevalence of the four major avian blood parasite genera. We used an extensive data on blood parasite infections and host ecology in 263 bird species from the Western Palearctic, combining species-specific data with a comparative approach to control for similarity in phenotype among host species due to the effects of common phylogenetic descent. Adult survival rate negatively correlated with the number of parasite species infecting a host species when controlling for similarity due to common descent and body mass. In addition, the prevalence of Haemoproteus, Plasmodium and Leucocytozoon was higher in species harbouring a richer parasite assemblage. These results suggest that the impact on host fitness caused by avian haematozoa may be underestimated in natural populations if the exacerbated virulence associated with exposure to multiple parasites is not taken into account.     

Haemoglobin concentration and body condition of nestling Great Tits Parus major : a comparison of first and second broods in two contrasting seasons

The physiological condition of nestling altricial birds depends on the quantity and quality of food delivered to them by parents. One indicator of the condition of Great Tit Parus major nestlings is the haemoglobin concentration in their blood. The present study demonstrates the influence of weather conditions (temperature and rainfall) on nestling haemoglobin concentrations during two consecutive breeding seasons in two different habitat types (parkland vs. woodland) in the city of Łódź in Central Poland. This influence probably results from the effects of weather on the trophic base of the Tits. Dry, hot weather strongly affected bush and herbal foliage later in the breeding season (mid-June to mid-July) in 2006, presumably by interfering with the development of herbivorous arthropod populations. This in turn caused food shortages for second broods of Great Tits, which resulted in nestlings having low haemoglobin levels. In the following year, temperature was on average lower, and rainfall was regular but not very heavy. These conditions enabled the development of arthropod assemblages, and the trophic base for birds was much richer. Haemoglobin concentrations in the blood of nestlings from second broods were significantly higher than those of first broods and, unexpectedly, second-brood nestlings in 2007 were on average in better physiological state than first-brood nestlings in 2006 in both habitats. The relationship between haemoglobin concentration, brood category and year was very similar to that for nestling body mass. However, it was independent of both body mass and brood size. In some years and under certain conditions, second broods can be more successful than first broods.     

Genetic covariance between components of male reproductive success: within‐pair vs. extra‐pair paternity in song sparrows

The evolutionary trajectories of reproductive systems, including both male and female multiple mating and hence polygyny and polyandry, are expected to depend on the additive genetic variances and covariances in and among components of male reproductive success achieved through different reproductive tactics. However, genetic covariances among key components of male reproductive success have not been estimated in wild populations. We used comprehensive paternity data from socially monogamous but genetically polygynandrous song sparrows (Melospiza melodia) to estimate additive genetic variance and covariance in the total number of offspring a male sired per year outside his social pairings (i.e. his total extra‐pair reproductive success achieved through multiple mating) and his liability to sire offspring produced by his socially paired female (i.e. his success in defending within‐pair paternity). Both components of male fitness showed nonzero additive genetic variance, and the estimated genetic covariance was positive, implying that males with high additive genetic value for extra‐pair reproduction also have high additive genetic propensity to sire their socially paired female's offspring. There was consequently no evidence of a genetic or phenotypic trade‐off between male within‐pair paternity success and extra‐pair reproductive success. Such positive genetic covariance might be expected to facilitate ongoing evolution of polygyny and could also shape the ongoing evolution of polyandry through indirect selection.     

Ageing, reproductive value, and the evolution of lifetime fighting behaviour

The study of sexual selection has recently been enriched by an explicit life history focus. This lifetime perspective has much to offer the field; however, most existing interdisciplinary exchanges have restricted themselves to the context of mate choice and associated phenomena. The present study explores the consequences of an explicit life history view upon the evolution of male–male contest competition. Key to this view is the fact that fighting typically has lifetime consequences, and thus the costs involved with contests are best considered in lifetime currencies such as residual reproductive value. The rate of contemporary contest cost accrual may vary among contestants due to differences between them in what they 'stand to lose', in terms of future reproductive opportunities. It is also suggested that it may be fruitful to partition key life history parameters into components that are either dependent or independent of future choice of mating strategy. Using a simple simulation, it is demonstrated that the optimum pattern of lifetime contest participation may vary depending upon lifetime variation in 'strategy-independent' components of reproductive value (such as the rate of mortality experienced in contexts unrelated to mating behaviour). In line with previous models of age-specific sexual advertisement, increasing lifetime aggression appears as the most favoured strategy; however, young age aggression is predicted if resource holding potential is expected to decline with age irrespective of prior contest participation. The model is discussed, along with key concepts surrounding the life history viewpoint, in light of prior life history/sexual selection models and the existing empirical data regarding lifetime fighting strategies in the wild.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 88 , 565–578.     

Experimental manipulation of tail length in female barn swallows (Hirundo rustica) affects their future reproductive success

Previous studies have shown no significant effect of experimentaltail length manipulation in female barn swallows (Hirundo rustica)at the beginning of a breeding season on reproductive successor behavior during that breeding season. In the present study,we investigate if tail length manipulation had any effect onreproductive performance the following year, the so-called long-termeffect, in contrast to the short-term effects already studied.We found that females with experimentally elongated externaltail feathers at the beginning of a breeding season producedless offspring during the breeding season the following yearthan did females with shortened or unmanipulated tails. Theseresults suggest that tail elongation caused flight deficienciesthat deteriorated the condition of females and eventually reducedreproductive success. The finding of long-term effects but nosignificant short-term effects for female tail elongation suggeststhat female barn swallows have the ability to adjust immediateparental investment. Detrimental effects of long tails in femalesin terms of decreased reproductive success might explain whyfemale tails are not as long as those of males. Finally, femalesmated to long-tailed (sexually attractive) males decreased theirreproductive success the following year more than did femalesmated to short-tailed males, possibly owing to differentialparental effort causing a deterioration of their condition.     

MalAvi: a public database of malaria parasites and related haemosporidians in avian hosts based on mitochondrial cytochrome b lineages

Research in avian blood parasites has seen a remarkable increase since the introduction of polymerase chain reaction-based methods for parasite identification. New data are revealing complex multihost-multiparasite systems which are difficult to understand without good knowledge of the host range and geographical distribution of the parasite lineages. However, such information is currently difficult to obtain from the literature, or from general repositories such as GenBank, mainly because (i) different research groups use different parasite lineage names, (ii) GenBank entries frequently refer only to the first host and locality at which each parasite was sampled, and (iii) different researchers use different gene fragments to identify parasite lineages. We propose a unified database of avian blood parasites of the genera Plasmodium, Haemoproteus and Leucocytozoon identified by a partial region of their cytochrome b sequences. The database uses a standardized nomenclature to remove synonymy, and concentrates all available information about each parasite in a public reference site, thereby facilitating access to all researchers. Initial data include a list of host species and localities, as well as genetic markers that can be used for phylogenetical analyses. The database is free to download and will be regularly updated by the authors. Prior to publication of new lineages, we encourage researchers to assign names to match the existing database. We anticipate that the value of the database as a source for determining host range and geographical distribution of the parasites will grow with its size and substantially enhance the understanding of this remarkably diverse group of parasites.     

Life expectancy,maximum longevity and lifetime reproductive success in female Thornicroft's giraffe in Zambia

Gestation and longevity scale with body mass across taxa, yet within size dimorphic taxa, males tend to have reduced lifespans compared with females. Testing life history models, and accounting for sex differences in longevity, requires obtaining accurate longitudinal data from wild populations. We provide the first report describing key life history parameters from a long‐term study of giraffes in Africa. We followed a population of Thornicroft's giraffe (Giraffa camelopardalis thornicrofti) in Zambia for over 40 years. Maximum longevity among females was approximately 28 years, with lifespan accounting for 81% of the variance in lifetime reproductive success. Average adult female life expectancy was no different than average adult male life expectancy. However, the breeding lifespan of males was about half that of females, while maximum lifespan of males was 75% that of females. Our findings support the suggestion that sex differences in maximum lifespan arise from stronger selection for lengthy lives in females than in males. Among females, longer lives are associated with greater reproductive output.     

Sex‐specific pathways of parental age effects on offspring lifetime reproductive success in a long‐lived seabird

The conditions under which individuals are reared vary and sensitivity of offspring to such variation is often sex‐dependent. Parental age is one important natal condition with consequences for aspects of offspring fitness, but reports are mostly limited to short‐term fitness consequences and do not take into account offspring sex. Here we used individual‐based data from a large colony of a long‐lived seabird, the common tern Sterna hirundo, to investigate longitudinal long‐term fitness consequences of parental age in relation to both offspring and parental sex. We found that recruited daughters from older mothers suffered from reduced annual reproductive success. Recruited sons from older fathers were found to suffer from reduced life span. Both effects translated to reductions in offspring lifetime reproductive success. Besides revealing novel sex‐specific pathways of transgenerational parental age effects on offspring fitness, which inspire studies of potential underlying mechanisms, our analyses show that reproductive senescence is only observed in the common tern when including transgenerational age effects. In general, our study shows that estimates of selective pressures underlying the evolution of senescence, as well as processes such as age‐dependent mate choice and sex allocation, will depend on whether causal transgenerational effects exist and are taken into account.     

Lifespan and age,but not residual reproductive value or condition,are related to behaviour in wild field crickets

Individuals frequently show long‐term consistency in behaviour over their lifetimes, referred to as “personality.” Various models, revolving around the use of resources and how they are valued by individuals, attempt to explain the maintenance of these different behavioural types within a population, and evaluating them is the key for understanding the evolution of behavioural variation. The pace‐of‐life syndrome hypothesis suggests that differences in personalities result from divergent life‐history strategies, with more active/risk‐taking individuals reproducing rapidly but dying young. However, studies of wild animals provide only limited support for key elements of this and related hypotheses, such as a negative relationship between residual reproductive value and activity. Furthermore, alternative models make divergent predictions regarding the relationship between risk‐taking behaviours and variables consistent in the short‐term, such as condition. To test these predictions, we regularly measured willingness to leave a shelter and the activity level of wild adult field crickets (Gryllus campestris) at both short and long intervals over their entire adult lives. We found some support for a pace‐of‐life syndrome influencing personality, as lifespan was negatively related to willingness to leave the shelter and activity. Crickets did not appear to protect their “assets” however, as estimates of residual reproductive value were not related to behaviour. Although there was considerable variance attributed to the short‐term consistency, neither trait was affected by phenotypic condition, failing to support either of the models we tested. Our study confirms that behaviours may covary with some life‐history traits and highlights the scales of temporal consistency that are more difficult to explain.