Abstract I studied the structure of European breeding forest bird communities on several spatial scales focusing on heterospecific attraction among birds (i.e., the attraction of individuals to the company of interspecifics). Namely, I examined how heterospecific attraction affects habitat selection in migrant birds and the potential role of predation risk in enhancing heterospecific attraction during breeding with particular emphasis regarding the interaction between resident and migrant birds. Geographically, low densities and low relative proportions of resident titmice (Parus and Aegithalos spp.) were associated with harsh winter conditions. The densities of northern European titmice populations are suggested to be lower than expected on the basis of summer productivity potentially causing geographical variation with respect to the interactions between resident and migrant birds. As expected, the associations between titmice and migrants appear stronger and more positive in northern Europe than elsewhere. Heterospecific attraction in habitat selection among migrant species was studied both experimentally and theoretically. An increased density of titmice resulted in a higher number and abundance of migrant species than the removal treatment, suggesting that resident birds are used as cues for locating profitable breeding sites. From a theoretical perspective and under most conditions, the use of heterospecific cues proved to be a better habitat selection strategy than selection of sites based on direct assessment of the relative quality of habitat patches. Only when interactions (both positive and negative) between migrants and residents were weak and sampling costs of both strategies were about equivalent, did individuals using direct sampling gain in fitness. Heterospecific attraction during breeding in relation to predation risk was assessed by examining the spatial distribution of birds. Both experimentally increased perceived predation risk and naturally occurring predation risk created by the presence of sparrowhawk (Accipiter nisus) i.e., relative to the vicinity of nesting hawk, resulted in more clumped distribution of birds than areas of lower risk. Around sparrowhawks nest, however, clumping was apparent for only one forest type and only among study plots including both large (≥ 20 g, preferred prey) and small birds (< 20 g). To conclude, heterospecific attraction of migrants to resident birds contributes to the structure of local avian communities in forest landscapes. Heterospecific attraction among birds is strengthened by increased predation risk causing variation in species interactions when considered in a landscape perspective.

Abstract Mitochondrial DNA sequences were used to study the phylogeny, population structure and colonisation history of Parus species. The phylogenetic relationships of seven European and three American species were examined by sequencing a part of the cytochrome b gene. Phylogenetically the closest species were the great tit (Parus major) and the blue tit (P. caeruleus). Subgenus Poecile was divided into two clades, one consisting of the Siberian tit (P. cinctus), the Carolina chickadee (P. carolinensis) and the Black-capped chickadee (P. atricapillus) and the other consisting of the marsh tit (P. palustris) and the willow tit (P. montanus). The coal tit (P. ater) and the crested tit (P. cristatus) did not group with any of the species studied. The population structure and the colonisation history of the willow tit, the great tit and the blue tit were examined by using control region sequences. The results suggest that the historical effective population size in the willow tit has been large and not contracted by the last ice age. Current gene flow must also be extensive as no population structuring was detected. No population structuring was evident either in the great tit and the populations showed distinctive signs of a recent population expansion. The patterns of genetic variation probably reflect a population bottleneck during the ice age, and a recolonisation of the European continent thereafter, presumably from a refugium situated in the Balkans. Two maternal lineages were found in the blue tit. The southern lineage was restricted to the Iberian peninsula whereas the northern lineage was detected from all the populations. The colonisation history has been similar to the one suggested for the great tit. The southern lineage, however, may have survived the ice age in a different refugium in the Iberian peninsula and was not as successful as the northern lineage in colonising available regions when the ice retreated. Both, the blue tit and the great tit have continued to expand their distribution northwards during this century and gene flow plays an important role in homogenising the populations.

This thesis evaluates the vigilance parameters of two species of tits affected by the presence of a predator in wintertime. During preferential experiments, tits have had a choice of two feeders in the vicinity of the installed dummy predator. For that purpose was used a dummy sparrowhawk, incomplete or occluded sparrowhawk torsos, and harmless pigeon. It is known that the tits are able to recognize dangerousness presented by the dummy, and according to expected risk dare to visit one of the feeders. It leads to a question whether the tits are somehow influenced by the presence of the dummies, and if so, how specifically are they influenced. It turned out, that the tits in presence of a dangerous dummy significantly increased their vigilance. Both observed species at the feeders behave oppositely. Behaviour of all the birds at the feeder is also affected by their total count at the precise moment and by the presence of a dummy at the other feeder.

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Understanding the genetic basis of fitness differences has been a major goal for evolutionary biologists over the last two decades. Although there are many studies investigating how natural selection can promote local adaptation, few have succeeded to find the link between genotype and fitness of the phenotype. Polymorphic genes of the major histocompatibility complex (Mhc) are excellent candidates for such associations as they are a central component of the vertebrate immune system, playing an important role in parasite resistance, and hence can have direct effects on survival of their bearers. Although associations between Mhc and disease resistance are frequently documented, the epidemiological basis of the host-parasite interaction is often lacking and few studies have investigated the role that Mhc genes play in individual variation in fitness; thus comparatively little is known about the fitness consequences of Mhc in wild populations. Furthermore, the majority of work to date has involved testing associations between Mhc genotypes and disease. However, the mechanism by which any direct selection on the Mhc acts, depends on how genotypes map to the functional properties of Mhc molecules. The aim of this thesis was to characterize Mhc alleles in terms of their predicted functional properties and to investigate whether and how selection operates on Mhc class I functional variation using the great tit (Parus major) population at Wytham Woods as a model host species. Through a comprehensive characterization effort and the use of 454 pyrosequencing platform, I performed a detailed analysis of genetic variation at Mhc class I exon 3 and grouped alleles with similar antigen-binding affinities into supertypes to classify functionally distinct Mhc types. There was extreme complexity at the Mhc class I of the great tit both in terms of allelic diversity and gene number. A total of 862 alleles were detected from 857 individuals; the highest number yet characterized in a wild bird species. The functional alleles were clustered into 17 supertypes; there was clear evidence that functional alleles were under strong balancing selection. To understand the role of Mhc in disease resistance, I examined the linkage between Mhc supertypes, Plasmodium infection and great tit survival, and showed that certain functional variants of Mhc confer resistance to two divergent Plasmodium parasite species that are common in the environment. I further investigated the fitness consequences of functional variation at Mhc, using mark-recapture methods and long-term breeding data; and tested the hypotheses that selection: (i) maximizes Mhc diversity; (ii) optimizes Mhc diversity, or (iii) favours specific functional variants. I found that the presence of three different supertypes was associated with three different components of individual fitness: adult survival, annual recruitment probabilities and lifetime reproductive success. In contrast, there was no evidence for a selective advantage of Mhc functional diversity, either in terms of maximal or optimal supertype diversity. Finally, I explored the role that Mhc plays in female mate choice decisions and examined the reproductive fitness consequences of Mhc-dependent mating patterns. There was little evidence to suggest that functional dissimilarity at Mhc has any influence on female mate choice decisions or that dissimilarity at Mhc affects the reproductive output of the social pair. Overall, this thesis provides strong support for the suggestion that selection favours specific functional variants of Mhc, possibly as a result of supertype-specific resistance or susceptibility to parasites that exert strong selective pressures on their hosts; whereas there is no support for selection favouring maximal or optimal Mhc diversity. More importantly it demonstrates that functional variants of Mhc class I loci are an important determinant of individual fitness in natural populations.

Oxycarenus lavaterae is species of Heteroptera and possessing pink blots on corium and distinctive, gleaming membranaceous wings. This appearance could correspond to the definition of a warning color. The design is similar to other coreoid Heteroptera, which live in the Czech Republic; though Oxycarenus lavaterae is a species originating from Mediterranean and quickly spreading north. In Czech Republic it is a new species and predators thus have only short experience with it.The information about chemical protection of Oxycarenus lavaterae is weak and the effect on predators has never been tested. The characteristic behaviour for this species is creating large aggregations, primarily at the time of hibernation. At that time, several thousands of individuals are gathered in apertures or at the surface of tree bark. The aggregation may enhance the warning appearance of this species. The aim of this study was to test the response of bird predators to the adult individuals of Oxycarenus lavaterae. Three species of insectivorous birds differing in the level of foraging and diet specialization was chosen as predator (namely - Great tit (Parus major), Blue tit (Cyanistes caeruleus), Eurasian blackcap (Sylvia atricapilla)). Unmodified individuals of Oxycarenus lavaterae were served to these predators. In the case of the Parus major, the aggregation of Oxycarenus lavaterae (about 100 pieces) was also presented to test the effect of gregarious behavior on the warning signal. This study showed that the Parus major and the Sylvia atricapilla attacked the individual Oxycarenus more often than the Cyanistes caeruleus showing high level of restraint. In experiments with aggregatedOxycarenus lavaterae Parus major attacked them less often than when presented solitarily. However, after eating some Oxycarenus lavaterae, the Parus major showed symptoms of disgust and loss of appetite.

The present research was conducted to assess the effect of Sparrowhawk predation on the tit population of Wytham Woods, Oxford. Chapter 1 describes the history of the Wytham hawk population until this study began and the nesting biology of the hawks during the study. Six to nine pairs of hawks settled in the wood each year, but reproductive success was low due to pesticide contamination. Chapter 2 shows that tit nesting success was reduced when they nested near hawk nests. Circumstantial evidence is presented for reduced tit nesting success throughout the wood since the return of the hawks. Chapter 3 examines rates of hawk predation during the nesting period. Findings indicate that hunting rates and the percentage of the diet formed by tits are regulated by prey availability or vulnerability, with highest predation rates occurring at the time that tits fledge. In Chapter 4 the selection of tits by hawks is analysed. Results indicate that on the basis of brood and physical characteristics adult tits were selected on the basis of availability and juvenile tits were selected primarily by date of fledging. The ratio of adult to juveniles taken differed between years and was thought to be related to the number of tits available per hawk each year. Chapter 5 presents estimates showing that 22-42% of each segment of the tit population was killed by hawks each year. The effects of these losses are discussed, concentrating on the shift in the structure of the tit breeding population which has occurred since the hawks returned to the wood. In Chapter 6 the findings of the study are compared to the findings of previous predator-prey research and the attributes of Wytham as an area for studying predation discussed.

Eggshell coloration in bird clutches shows a striking variability within species which has not yet been fully explained. Its character is determined by the deposition of two main pigments: blue-green biliverdin is responsible for the background colour while brown-red protoporphyrin is associated with the dark spot pattern. Considering the role and matabolism of these two pigments in the avian organism it was suggested that they might have an important impact on the oxidative stress levels and their deposition into the eggshell is therefore suggested to possibly reflect the body condition of laying females during the laying periods. This is also the basic assumption for the signalling hypothesis of eggshell coloration which predicts the eggshell appearance to reflect the female body condition and individual health status or directly indicate aenemia in birds (aenemic hypothesis). Here it was tested whether there is a relationship between parameters representing the body condition of female great tits (Parus major) and the characteristics of protoporphyrin maculation of their eggs. Female body condition was expressed by standardized body weight and the selected haematological parameters (heterophil to lymphocyte ratio and relative immature erythrocyte counts). Eggshell coloration was characterized by spot colour (hue, saturation and brightness), spot counts and the reflectance of the background colour. It was found that females with higher heterophil to lymphocyte ratio laid eggs with more spots and higher reflectance of the background colour in some nesting seasons. Eggs with more spots on its surface were also laid by females with higher immature erythrocyte counts. These results suggest that more intensive deposition of protoporfyring into the eggsell can indicate worse body condition of the laying females. On the other hand, it was also found that heavier females laid eggs with lower reflectance of the background colour. Despite this discrepancy, these results are not inconsistent with the pressumptions of the signalling hypothesis and they partially support the aenemia hypothesis. However, the above mentioned dependencies were inconsistent among the nesting seasons, indicating that further important determinants must be considered in the avian eggshell coloration.

Abstract Animals need information about local conditions to make optimal fitness-enhancing decisions such as where to breed. Information can be acquired by personal sampling of the environment, but it can also be acquired from other individuals. The latter is termed social information use. Social information use has gained a lot of attention in modern ecology because it affects principal ecological phenomena such as animal distribution and resource use. Social information use is not restricted to obviously cognitive mammals and birds but is also found in e.g. reptiles, fish and insects. Social information use studies have thus far been concentrated on situations with one social information user and one (often the same) source species. The community-wide consequences of social information use have almost exclusively been considered in theoretical studies. In this thesis, I studied empirically social information use in the nest site selection within and between species in a cavity-nesting bird community consisting of the collared flycatcher (Ficedula albicollis), the great tit (Parus major) and the blue tit (P. caeruleus). I studied social information use on two time scales: social information gathered just before a breeding attempt, and social information gathered already during the previous breeding season for the following year’s breeding attempt. I used experiments in which different white geometric symbols represented nest site choices of earlier settled tutors and empty nest boxes, and I observed the symbol choices of later-breeding individuals. The symbol approach eradicates bias from innate and learned preferences enabling strong inference. My results demonstrate that collared flycatchers use social information from both con- and heterospecific tutors in different situations in a flexible manner. Hence, social information use seems to be context-dependent. Furthermore, I show that great tits avoid choosing nest site characteristics which were associated with either con- or heterospecifics nests the previous year and prefer symbols which depicted an empty nest box the previous year, probably to avoid nest ectoparasites. I also show that in great tits the male has greater influence on nest site selection than previously assumed even though the female builds the nest. My thesis deepens our understanding about the complexity of social information use and highlights its significance in future ecological research. / Tiivistelmä Eläimet tarvitsevat informaatiota paikallisista olosuhteista tehdäkseen edullisia päätöksiä esimerkiksi siitä, missä lisääntyä. Informaatiota voidaan hankkia tutkimalla ympäristöä itse, mutta sitä voidaan hankkia myös muilta yksilöiltä. Jälkimmäistä kutsutaan sosiaaliseksi informaatioksi. Eläinten sosiaalisen informaation käyttö on saavuttanut viime aikoina paljon huomiota ekologisessa tutkimuksessa, koska se vaikuttaa tärkeisiin ekologisiin ilmiöihin, kuten eläinten levinneisyyteen ja resurssien käyttöön. Sosiaalinen informaation käyttö ei rajoitu vain nisäkkäisiin ja lintuihin, vaan sitä on havaittu myös esimerkiksi matelijoilla, kaloilla ja hyönteisillä. Sosiaalisen informaation käyttöä on tutkittu lähes yksinomaan lajien sisällä tai käyttäen ainoastaan yhtä sosiaalisen informaation lähdelajia. Yhteisötason vaikutuksia on pohdittu miltei pelkästään teoreettisissa tutkimuksissa. Tässä väitöskirjatyössä tutkin kokeellisesti sosiaalisen informaation käyttöä pesäpaikan valinnassa lajin sisällä ja lajien välillä kolopesivien lintujen yhteisössä sepelsiepolla (Ficedula albicollis), talitiaisella (Parus major) ja sinitiaisella (P. caeruleus). Otin tutkimuksissani huomioon kaksi aikatasoa: tutkin juuri ennen pesimisyritystä kerätyn sekä jo edellisen lisääntymiskauden aikana seuraavan vuoden pesintää varten hankitun sosiaalisen informaation käyttöä. Kokeissani käytin linnunpönttöihin kiinnitettyjä erilaisia valkoisia geometrisia symboleita, jotka edustivat aiemmin pesinnän aloittaneiden lintujen eli tuutoreiden pesäpaikanvalintoja. Seurasin tämän jälkeen myöhemmin pesimään saapuvien parien symbolivalintoja. Tulosteni perusteella sepelsiepot hankkivat sosiaalista informaatiota sekä lajitovereiltaan että tiaisilta joustavasti eri tilanteissa. Lisäksi osoitan, että talitiaiset välttävät valitsemasta pesäpaikkoja, jotka olivat asuttuina edellisenä vuonna, ja suosivat sellaisia pesäpaikkoja, joissa ei pesitty edellisenä vuonna - todennäköisesti välttääkseen kirppuja ja muita pesäloisia. Osoitan myös, että talitiaiskoirailla on suurempi vaikutus pesäpaikan valintaan kuin aikaisemmin on oletettu, vaikka naaraat rakentavat pesän. Väitöskirjatyöni syventää käsitystämme sosiaalisen informaation käytön monitahoisuudesta eläinkunnassa ja korostaa sen merkitystä ekologisessa tutkimuksessa.

L’évolution divergente est un processus clef générant de la biodiversité. Elle peut avoir lieu entre localités, via la réduction des flux de gènes, et au sein des localités via la spécialisation écologique. Dans le cas des systèmes parasitaires multi-hôtes, l’adaptation dépend des taux relatifs de flux de gènes des hôtes et des parasites entre différentes localités, ainsi que des échanges locaux de parasites entre différents types d’hôtes. En combinant génétique des populations et expérimentations sur le système composé de la puce Ceratophyllus gallinae et deux de ses hôtes, la mésange charbonnière Parus major et le gobe-mouche à collier Ficedula albicollis dans un habitat fragmenté, nous avons examiné comment l’adaptation et l’isolation génétique façonnent l’évolution des parasites. Nous avons aussi testé comment les choix d’habitat des hôtes pouvaient influencer la rencontre avec des populations de parasites spécialisées. Les analyses de microsatellites révèlent que les populations de puce sont différenciées à une échelle spatiale fine, et fréquemment entre espèces hôtes. De plus, des populations de parasites semblent adaptées à chaque type d’hôte. Cependant, aucune variation dans les choix d’habitats par rapport aux parasites n’a été observée chez les hôtes. Enfin, la réponse des hôtes aux parasites variait entre nos deux zones réplica ; l’histoire des populations d’hôtes pourrait donc influer sur la coevolution avec leurs parasites. Ce système semble donc localement façonné à la fois par une isolation génétique et une sélection par différents hôtes. L’étude de nouveaux sites permettraient d’évaluer si cette évolution divergente peut être génératrice de biodiversité / Divergent evolution is a key process generating biodiversity. This can occur between localities, through reduced gene flow followed by local adaptation or genetic drift, and within localities through ecological specialization. In the case of multi-host parasite systems, adaptation can be driven by the relative rate of host-parasite gene flow among spatially isolated populations, and the amount of parasite exchange among local host types. Combining population genetics and field experiments, we examined how adaptation and genetic isolation shape parasite evolution. Focusing on the hen flea Ceratophyllus gallinae, a presumed host generalist, and two of its hosts, the great tit Parus major and the collared flycatcher Ficedula albicollis, we investigated parasite population structure and adaptation within a fragmented landscape. Additionally, we tested how hosts can influence encounter rates with specialized flea populations through their habitat choice. Neutral markers analyses show that flea populations are genetically differentiated at fine spatial scales, and frequently between the two host species. Evidence for parasite adaptation to each host type were also observed. Host specialization may therefore be ongoing in hen fleas. However, birds did not show specific habitat choice strategies regarding flea-infested nests. Host responses differed between two replicate sites, indicating that local population history may impact parasite evolution. Both isolation and host-based selection are therefore acting on hen flea populations at a local scale. Investigations in new localities will help to assess to what extend this divergent evolution may generate biodiversity