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Behaviour encompasses all interactions of an animal with other organisms and with its environment. Studying animal behaviour can provide important information for species conservation and management. In this thesis, I aimed at closing fundamental knowledge gaps on different behavioural-ecological aspects of the three migratory species of Columbiformes (order of doves and pigeons) native to Europe. The species studied include one of the most rapidly declining breeding birds in Europe, the European Turtle Dove (Streptopelia turtur). As a Palearctic-African migratory species, it is the only long-distance migrant among the European native wild Columbiformes. On the contrary, Common Woodpigeons (Columba palumbus) and Stock Doves (Columba oenas) are both short-distance migrants. They belong to the most common European breeding birds or have a stable population trend, respectively. All three species are regularly hunted in several European countries. In my thesis, I examined the wintering areas, migration flyways and phenology of European Turtle Doves by means of analysing feather-isotope values (chapter 1) and satellite tracking data (chapter 2). My findings highlight the use of several migration flyways and suggest that individuals breeding in different parts of Europe may occupy separate African wintering grounds. Tracking of Common Woodpigeons with GPS-GSM transmitters (chapter 3) showed that individuals breeding in Germany are facultative partial migrants, which can switch their migratory strategy (resident vs. migrant) between years. Tracking data evaluated along with land cover data indicated that both European Turtle Doves and Common Woodpigeons adapt their foraging areas and distances to the availability of food resources (chapters 2 and 3). A comparative assessment of diet components, analysed from faecal samples through DNA metabarcoding (chapter 4), revealed a variation in the presence and frequency of occurrence of diet items between the three species. Identified diet components were mainly seed-bearing plants (Spermatopsida). Furthermore, comparisons with previous studies suggest distinct regional intraspecific differences in diet composition. An evaluation of haemosporidian parasite infections (Plasmodium sp., Haemoproteus sp. and Leucocytozoon sp.) from avian blood samples (chapter 5) demonstrated interspecific differences in lineage diversity, overall and genus-specific prevalence. The observed infection pattern supported the assumption that long-distance migrants harbour a higher parasite prevalence and diversity compared to resident or short-distance migratory species. Summarising, the findings of this thesis (i) enable a better interpretation of different behaviours observed in the Columbiformes, (ii) help to comprehend how behavioural habits are influenced by ecological causation and (iii) emphasize the distinct behavioural diversity and plasticity present among species as well as individuals. Furthermore, the results contribute to a greater understanding of the general and specific ecological requirements of the species of Columbiformes. This can help to optimise present or to plan effective future management and conservation strategies that reconcile the challenges of game bird management on the one hand and species conservation on the other hand.

Although different predictive models forecast that climate change will alter the distribution and incidence of parasitic diseases, few studies have investigated how microclimatic changes may affect host-parasite relationships. In this study, we experimentally increased the temperature inside nest boxes of the blue tit Cyanistes caeruleus during the nestling period at two different latitudes (central Spain and central Germany) to determine its effect on parasite abundance. The two localities have contrasting climate conditions: the southern one in Spain is warmer and drier than the northern one in Germany. Consistent with this, we observed that the parasitic fauna in nests at the two localities differs. The flea species Ceratophyllus gallinae was more abundant in the northern locality, while the blowfly species Protocalliphora azurea and biting midge species of the genus Culicoides were more abundant in the southern one, as were blood parasites. Moreover, dermanyssid mites and blackflies (Simuliidae) were observed only in the southern locality. The temperature inside nest boxes was increased using heat mats placed underneath the nest material during the nestling period (day 3 to day13 post-hatching). Compared with control nests, the average temperature in heated nests increased by 2.24 °C and 1.35 °C at night in Spain and Germany, respectively. Consequently, the average relative humidity in heated versus control nests decreased 4.93 and 0.82 units in Spain and Germany, respectively. The abundance of blowfly pupae in the heated nests was significantly lower than that of control nests at both localities. The abundance of larval fleas was also lower in the heated nests, but only at the Spanish locality. Infection by the blood parasites Haemoproteus/Plasmodium was higher in males attending the heated nests in Germany, and the control nests in Spain. Moreover, both male body mass and nestling wing length were negatively related to the abundance of larval fleas. In conclusion, our results indicate that increased temperature at the nestling stage may affect the fitness of blue tits by altering parasite prevalence rates.

Background. Avian Haemosporida are vector-borne parasites that commonly infect Passeriformes. Molecular analyses revealed a high number of different lineages and lineage specific traits like prevalence and host-specificity, but knowledge of parasite prevalence and lineage diversity in wild birds in Central Germany is still lacking. Results. Blood samples from a total of 238 adult and 122 nestling songbirds belonging to six species were investigated for infections with avian haemosporidian genera and lineages (Haemoproteus spp., Plasmodium spp., Leucocytozoon spp.) and Trypanosoma avium using PCR, targeting the parasite mitochondrial cytochrome b gene and 18S ribosomal RNA. In total, the prevalence in adult birds was 31.3% infected with Haemoproteus, 12.5% with Plasmodium and 71.0% with Leucocytozoon (nestlings excluded). None of the tested birds was infected with Trypanosoma avium. Only in two nestling birds, aged 12-17 days, a Leucocytozoon spp. infection was proven. Among 225 successfully sequenced samples, we found four Haemoproteus, three Plasmodium and 19 Leucocytozoon lineages, including two new Leucocytozoon lineages. Furthermore, we report two new host-lineage associations.Conclusions. As first study investigating avian haemosporidian parasites in Central Germany, we provide new information on genetic diversity of Haemosporida infecting Passeriformes. We show that even with a small sample size new lineages as well as previously unknown linkages between certain lineages and host species can be detected. This may help to elucidate the diversity of lineages as well as lineage-host-connections of avian Haemosporida.

Avian trichomonosis is a widespread disease in columbids and other birds, caused by ingestion of the unicellular flagellate Trichomonas gallinae which proliferate primarily in the upper respiratory tracts. Studies using genetic analyses have determined some highly pathogenic lineages in birds, but the prevalence and distribution of potentially pathogenic and non-pathogenic T. gallinae lineages in wild birds is still not well known. We examined 440 oral swab samples of 35 bird species collected between 2015 and 2017 in Hesse, central Germany, for Trichomonas spp. infection and for determining the genetic lineages. Of these birds, 152 individuals were caught in the wild and 288 individuals were admitted from the wild to a veterinary clinic. The overall Trichomonas spp. prevalence was 35.6%. We observed significant differences between bird orders, with the highest prevalence in owls (58%) and columbids (50%), while other orders had slightly lower prevalences, with 36% in Accipitriformes, 28% in Falconiformes and 28% in Passeriformes. Among 71 successfully sequenced samples, we found 13 different haplotypes, including two previously described common lineages A/B (20 samples) and C/V/N (36 samples). The lineage A/B has been described as pathogenic, causing lesions and mortality in columbids, raptors and finches. This lineage was found in 11 of the 35 species, including columbids (feral pigeon, woodpigeon, stock dove), passerines (greenfinch, chaffinch, blackbird) and raptors (common kestrel, sparrowhawk, red kite, peregrine falcon and common buzzard). One new lineage (R) was found in a sample of a chaffinch. In conclusion, we found that the prevalence of Trichomonas spp. infection in wild birds was high overall, and the potentially pathogenic lineage A/B was widespread. Our findings are worrying, as epidemic outbreaks of trichomonosis have already been observed in Germany in several years and can have severe negative effects on bird populations. This disease may add to the multiple pressures that birds face in areas under high land-use intensity.