El uso de señales múltiples de calidad es común en numerosas especies, pero este hecho no es fácil de explicar. Las presiones fluctuantes del ambiente podrían tener un rol importante en el origen y mantenimiento de las señales múltiples, y las implicaciones evolutivas de esta hipótesis enfatizan la importancia de realizar nuevos estudios sobre señales múltiples. En esta tesis se realizaron diferentes estudios sobre la señalización múltiple del plumaje de dos especies de aves: El carbonero común (Parus major) y el lúgano (Carduelis spinus). En el primer capítulo se examinó la banda alar amarilla del lúgano, un ornamento sexual basado en carotenoides. Se vio que machos con bandas alares mayores eran más rápidos resolviendo un problema de forrajeo. Esto sugiere la existencia de una selección sexual de habilidades cognitivas en el lúgano. En el segundo capítulo, estudiamos la función del babero negro del lúgano como señal de la personalidad del individuo. Descubrimos que lúganos con baberos de mayor tamaño mostraban tendencias exploratorias más rápidas. Este hallazgo apoya la idea de que los ornamentos del plumaje pueden funcionar como señales de la personalidad del individuo. En el tercer capítulo se examinó cómo las señales múltiples pueden definir el comportamiento sexual extra pareja. Se pudo constatar que la respuesta agonística y la paternidad de machos de carbonero dependía de la interacción entre la corbata negra y la coloración amarilla del pecho del macho, sugiriendo la existencia de diferentes estrategias reproductivas de acuerdo a la calidad individual. Por último, examinamos las posibles interacciones entre ornamentos sexuales y la familiaridad, mediante experimentos de selección de pareja en lúganos. Nuestros resultados sugieren que la familiaridad puede ser tan importante como los ornamentos sexuales a la hora de determinar los criterios de selección de la hembra. En conclusión, esta tesis profundiza en el hecho de que las diferentes cualidades de un individuo, reflejadas en distintas señales múltiples, tienen el potencial de ser parte de diferentes estrategias válidas en selección sexual y social, permitiendo una selección más plástica. Esta plasticidad de selección podría ser uno de los mecanismos tras el origen y mantenimiento de las señales múltiples. / In sexual or social selection processes, animals employ traits that signal qualities. The use of multiple signals is known to be well spread in numerous species, but the ultimate reasons for using more than one single signal are not easy to explain. Why would animals invest in several different signals, instead of focusing on only one? Traditionally, the adaptive hypotheses formulated to explain the existence of multiple signalling have been framed into static scenarios, under constant selection pressures. However, there is increasing awareness of the need to widen this static framework, by taking into account the selection plasticity produced by spatial and temporal environmental heterogeneity. Fluctuating ecological and social environments could have an important role in the origin and maintenance of multiple signals. In an environment where changes happen faster every day, multiple signalling would allow a more flexible, dynamic selection, increasing the odds of survival and fitness. The evolutionary implications of this hypothesis highlight the importance of novel studies in multiple signalling. In this thesis, we performed several such experiments on the Eurasian siskin (Carduelis spinus) and the Great tit (Parus major). They are two passerine species that show ornaments based on melanins and carotenoids, which makes them a particularly suitable models for the study of multiple signalling. In the first chapter, the signalling function of the yellow wing stripe of the Eurasian siskin, a carotenoid based sexual ornament, was examined. A problem solving experiment showed that male siskins with longer yellow wing stripes were better foragers. These resuls suggest the existence of sexual selection for cognitive abilities. In the second chapter, we studied the function of the black bib of the Eurasian siskin as a potential source of information about the personality of the individual. We examined the exploratory behaviour of male siskins, finding that those with larger black bibs had a shorter approaching latency to a novel object. These results support the idea that plumage structures could give information about the personality of its bearer. The results of these two chapters show that colour signals based on different pigments have separate functions in the siskin, allowing multiple criteria in sexual (and social) selection. The third chapter examined the effects of different multiple colour signals on the extra pair sexual behaviour of the great tit. By measuring the response of different males to conspecific male intrusions, and the within pair paternity of males depending on their colour traits, we could observe that different combinations of traits where related to the intensity of nest defence, and implied differences in paternity loss. These findings suggest that males might be using different strategies to maximize their qualities. In the last chapter, we tested the potential interactions between colour sexual ornaments and the previous experience, by sexual selection experiments in siskins. Our results suggest that familiarity adds to attractiveness when female siskins choose a mate. At least in some species, females are using multiple criteria in mate choice, not necessarily related to external signals of quality. In conclusion, this thesis stress that multiple qualities, signalled by different colour traits, have the potential to be part of different successful social and sexual mate choice strategies, aiding a more plastic selection. Our results support the hypothesis that selection plasticity could be one of the mechanisms behind the origin and maintenance of multiple signals

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Personality and individual differences in reactions of the Great tit to aposematic prey were investigated. The aim of this study was to assess differences in personality of forty Great tits and find out possible correlation to the reactions of these birds to aposematic prey, the fifth larval instar of firebug Pyrrhocoris apterus.

Inbreeding occurs when relatives mate and have offspring. Inbreeding depression is hypothesized to have influenced the evolution of mating systems and behavioural mechanisms of inbreeding avoidance in the animal kingdom. Inbreeding in the wild is difficult to measure, as in order to build a pedigree allowing us to identify matings between relatives, the identity of as many as possible members of a population needs to be known. For a long time, the main source of knowledge about inbreeding depression was based on laboratory and agricultural studies, which did not reflect the array of environmental pressures wild populations have to cope with. In consequence, the deleterious consequences of inbreeding have often been underestimated. This is problematic because accurate estimates of the effect size of inbreeding depression are needed to study the strength of selection on inbreeding avoidance mechanisms, and are also of importance to conservation genetics. The aim of this thesis was to use pedigree data to infer the occurrence and effects of inbreeding using over forty years of breeding events of the great tit Parus major from Wytham Woods, Oxfordshire. The effects of inbreeding on fitness were investigated across a life-history continuum, and across environments. I found that close inbreeding (f=0.25) resulted in pronounced inbreeding depression, which acted independently on hatching success, fledging success, and recruitment success, and reduced the number of fledged grand-offspring by 55%. My results therefore suggest that estimates of fitness costs of inbreeding must focus on the entire life cycle. I also show that the variation in the strength of inbreeding depression varies across environments, particularly so the more the environmental variable considered is linked to fitness. These results emphasise the need of using relevant environmental contrasts when investigating inbreeding by environment interactions. I further asked whether individuals involved in matings with relatives differed relative to individuals mating with unrelated partners. I did not find any evidence for clear predictors of inbreeding, and I show that inbreeding depression in our population is entirely independent of any tendency for low quality parental genotypes, or phenotypes, to inbreed. Neither did I find any evidence for active inbreeding avoidance: great tits did not mate less often with kin than expected based on several scenarios of random mating, nor did I find increased rates of extra-pair paternity among birds breeding with relatives. In fact, I observed quite the contrary, as birds mating with kin exhibited a higher than average rate of close inbreeding relative to all scenarios of random mating investigated, showed lower rates of extra-pair paternity and divorce than birds mated to unrelated partners. I hypothesise that cases of occasional inbreeding in this population may result from mis-imprinting or a related process whereby some birds develop particularly strong bonds that are at odds with all predictions of avoiding inbreeding. Finally, I asked to what extent natal dispersal, a behaviour that is often hypothesized to play an important role in avoiding inbreeding, indeed reduces the likelihood of inbreeding. I found that male and female individuals breeding with a relative dispersed over several-fold shorter distances than those outbreeding. This led to a 3.4 fold increase (2.3-5, 95% CI) in the likelihood of close inbreeding relative to the population average when individuals dispersed less than 200m. This thesis demonstrates that inbreeding has deleterious effects on a wild population of birds, occurring throughout an individual’s life, and is of varying strength across environments. My findings strongly support the theory that natal dispersal should be considered as a mechanism of prime importance for inbreeding avoidance.

v III. Abstract (EN) According to the Disposable soma theory, senescence is mainly influenced by adaptive allocation of resources among the physical growth, reproduction and self-maintaining processes, which depend on expected survival of an individual. The amount of allocated resources may be influenced by external environmental factors such as heavy metal pollution or by inner factor e.g. reproduction. The aim of my diploma thesis was to clarify the relationships between senescence, selected haematological traits, reproduction and efficiency of innate immunity mechanism. Moreover, we are interested in the role of heavy metal pollution in ageing and haematology. The heterophiles to lymphocytes ratio (H/L) was used as a marker of long-term stress caused by these physiological expenses. This study summarizes partial data collected within the long-term research of great tits (Parus major) in Prague, Czech Republic, I participated in. We have more than 300 samples of repeatedly captured individuals at our disposal. The structure of this unique dataset allows us to observe changes in the traits of our interest during an avian lifespan. Our results show that during aging, males experience a noticeable increase in the H/L ratio compared to females. Although we have not found the effect of age on the brood size,...

This thesis focuses on various factors affecting effectiveness of aposematic signals against avian predators. Adult, wild-caught as well as hand-reared juvenile great tits (Parus major) were used as predators in the experiments. The thesis consists of the following four studies. In the first study, we compared the reactions of great tits from two geographically distant populations toward aposematic firebugs (Pyrrhocoris apterus) and their non-aposematic artificially made colour variant. The birds from the Bohemian population mostly avoided aposematic firebugs and attacked non-aposematic variant. Finnish birds, which lacked experience with firebugs from their natural environment, were less hesitant to attack both firebug colour forms. Although the Bohemian birds avoided the aposematic prey variant, they were not more neophobic than Finnish birds. We conclude that the geographic differences in reactions of the birds to aposematic prey can be explained by a different population-specific experience of the birds with local aposematic prey communities. In the second study, we compared effectiveness of two chemical defence strategies in leaf beetle larvae (Chrysomela lapponica) against great tits. The birds avoided larvae devoid of external secretions after the first attack, which indicates the presence...

Avian malaria (Plasmodium spp.) is a popular model system to study the ecology and evolution of parasite-host-vector interactions in the wild. These studies have historically focused mostly on the avian hosts and the malaria parasites. Knowledge regarding the role of vectors is essential to our understanding of these wild systems, but has only very recently started to accumulate. This thesis aimed to contribute to this field by assessing mosquito-malaria-host associations for British mosquitoes and the role of mosquito ecology in shaping these parasite systems in a British woodland study site, using molecular, field ecology and statistical modelling methodologies. From the 12 mosquito species or species groups found, I showed that the Cx.pipiens/torrentium mosquito group is likely to have a major role in avian malaria transmission in Great Britain, while Cs. annulata may be transmitting P. circumflexum. I also demonstrated a positive spatial association between mosquito density per host and avian malaria prevalence, in accordance with theoretical expectations for malaria transmission. Findings here provide evidence that avian malaria transmission in British woodlands is limited mainly to June-August, being preceded by relapse of previous infections or, alternatively, by maintenance of chronic blood parasitaemia through the colder months; this agrees with theoretical expectations and findings elsewhere for temperate climates. This thesis also described local-scale spatial heterogeneity and seasonal variation in adult mosquito abundance within a British woodland where avian malaria is endemic, with differing patterns found between species or species groups. Spatially, variation in adult mosquito abundance was associated with microclimatic and landscape variables such as distances to mosquito breeding sites, microclimate and canopy height; seasonally, variation in mosquito abundance was associated with temperature and rainfall, alongside calendar date. The heterogeneity in mosquito parameters and associations with environmental variables found at a site where avian malaria is endemic highlights the need to anticipate such complexity when trying to understand Plasmodium transmission. By doing so, we further extend the potential of these parasite systems to improve our knowledge regarding the ecology and evolution of parasite-host-vector associations.