National Repository of Grey Literature 78 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Signalling of personality and stress response by secondary sexual traits in a socially monogamous passerine
Tesař, David ; Tomášek, Oldřich (advisor) ; Sedláček, Ondřej (referee)
Secondary sexual traits play an irreplaceable role in the reproduction of a range of animals and are used as quality and fitness sensors during pairing of individuals. Expression of these traits, ornamentes, can correlated with an individual's personal and behavioral strategies. In the case of melanin ornaments, not only the relationships with personal individuals are considered, but there is the possible connections with stress resistance and the level of stress responses too. This hypothesis is based on the pleiotropic effect of the melanocortin system, which can be used during melanogenesis but also in the production of hormones that contribute to range of stress responses. The aim of this work was to clarify the relationship between an individual's ornaments, his stress response and individuality in the barn swallows (Hirundo rustica rustica). In this work the relationship between selected ornaments and the stress reaction of the organism, stressed glucose levels measured 15 minutes after a stress stimulus, was tested. Both sexes showed a correlation between area of white tail spots and stress response. Only for males a relationship with the length of outermost tail feathers was found and a correlation with the color saturation of feathers on the throat was shown for females. The second part of...
Determinants of abundances in terrestrial vertebrates
Kundelová, Tereza ; Storch, David (advisor) ; Sedláček, Ondřej (referee)
The abundance of animals differs between species, however, they also vary in area and time. These differences relate to biotic and abiotic factors as well as to ecological characteristics of particular species. Studies focusing on these factors are aiming to answer the question; how and what influences the abundance of these species. Besides clarifying the dependence of abundance on particular factors, studies also try to ascertain which key factors are necessary for the determination of abundance. The most frequently studied factor is body size, but trophic level, specialization, net primary productivity, and competition also play a significant role in determination. However, all these factors explain only a small proportion of interspecific variability in abundances. This thesis focuses on terrestrial vertebrates; however, mainly on birds and mammals; since, these two taxa are the most studied. Key words: abundance, population density, terrestrial vertebrates, body size, competition, energy flux
Bird Communities Along the Altitudinal Gradient on Mt. Cameroon: Perspectives from Mist Nets
Petruf, Miroslav ; Sedláček, Ondřej (advisor) ; Lučan, Radek (referee)
in English Mt. Cameroon is a hotspot of diversity and endemism in Africa. Recent research of avian bird communities along the elevational gradient on Mt. Cameroon based on point counts has shown low-elevation plateau of species richness. At the same time, range-restricted montane populations of birds on Mt. Cameroon are unusually abundant if compared to lowland species. I analysed data on community composition, species richness and abundance of birds using an alternative quantitative method - 200 m of understory mist nets erected for three consecutive days across seven elevational plots along the forested gradient of the Mt. Cameroon. First, I looked at the technical limits of this method and confirmed the general opinion that they are better at detecting small birds below 33 g, and that they mostly detected fewer individuals after the first day and always detected fewer new species after the first day of mist-netting. Mist nets detected high proportions of ground-feeding and understory birds and low proportions of birds foraging in higher strata in the lowland forest, which has a scarce understory and a dense canopy. Mist nets recorded similar proportions of birds foraging in all forest strata in the vastly open mid-elevation forest, which has a dense herbaceous understory. They detected higher...
Spatial activity of birds and methods of its continuous monitoring
Havelka, Jan ; Sedláček, Ondřej (advisor) ; Kauzál, Ondřej (referee)
The aim of this work was to collect current knowledge of avian spatial aktivity focusing to its internal structure, using modern telemetry devices which allows continuous monitoring of small animal species. In the light of these new methods, avian home ranges seem to be more dynamic structures, changing during diurnal and nocturnal acitvities, breeding cycle, age, sex and social statut of a bird. Thanks to detailed radiotelemetry we can observe even secretive animal behaviour and its characteristics in three dimensions. Continual monitoring allows us to study migration in a detailed way, its influence to other parts of their annual cycle and to asses migration connectivity. In future these new information should be used for targeted conservation of endangered species.
Latitudinal and altitudinal trends in sperm morphology and estimated levels of promiscuity in passerine birds
Krejčířová, Zuzana ; Albrecht, Tomáš (advisor) ; Sedláček, Ondřej (referee)
Sexual promiscuity, whereby females copulate with more than one male, is a quite common phenomenon in socially monogamous birds, and especially in songbirds. This behavior is assumed to influence the evolution of various anatomical traits associated with male ability to outcompete other males in the process of sperm competition. High promiscuity is, in a multi- species comparison, associated with higher relative testis mass, but may also affect sperm phenotypes and other male phenotypes. Sperm morphology is clearly differentiated across avian species and some studies suggest that stabilizing post-copulatory selection on sperm length is responsible for a clear association of between male variation in sperm length and levels of promiscuity. However, the association between other phenotypic traits and promiscuity remains less clear. In this study, I focus on sperm characteristics in relation to the estimated levels of promiscuity in songbirds of tropical and temperate zone climates, and across an altitudinal gradient in the tropics. I found that the coefficient of variation in sperm length, both between males (CVbm) and within males (CVwm), was indeed a good index of promiscuity. I also reveal the size of cloacal protuberance as an anatomical trait intimately associated with the level of sperm...
Sheep grazing as a controversial tool of nature protection
Daňková, Tereza ; Malíček, Jiří (advisor) ; Sedláček, Ondřej (referee)
Sheep grazing is currently more and more used as a main type of management in protected areas. However, it seems that in many cases this type of management has a negative impact on a habitat or species of interest. This bachelor thesis try to demonstrate how a care about pastures in term of nature conservation should be applied in a selected area. There are examples of endangered species that are directly threatened by an unappropriate sheep grazing. Positive and negative influences of grazing, especially sheep grazing, are summarized.
Behaviour of avian predators to seed bugs (Lygaeoidea): effectiveness of chemical defence
Chalušová, Kateřina ; Exnerová, Alice (advisor) ; Sedláček, Ondřej (referee)
By warning signalling prey advertises its unpalatability to the predators. Typical examples are true bugs (Heteroptera) combining optical and chemical signals. The aim of this study was to find out the effectiveness of chemical defence against wild-caught adults of great tits (Parus major) and blue tits (Cyanistes caeruleus) and towards hand-reared juveniles of great tits. The tested prey were adults and larvae of two invasive species of genus Oxycarenus (Heteroptera: Oxycarenidae) (aposematic O. lavaterae, non-aposematic O. hyalinipennis), adults of Horvathiolus superbus (Heteroptera: Lygaeidae) and crickets (Gryllus assimilis) as a control prey. We were focusing on the influence of seed bugs to the initial reaction, the learning process and to the displays of discomfort behaviour in tits. Reactions affected by the tit species, age and sex were compared in adults. Juveniles were divided into two independent experimental groups, one group was offered adults of genus Oxycarenus, the second was offered sunflower (Helianthus sp.) or Digitalis sp. seed fed adults of H. superbus. The first bug offered did not elicit an initial aversive reaction in tits, but birds reacted aversively to the bugs after having further handling experience. All juveniles, contrary to the adult tits, attacked at least one bug...
Latitudinal trend in feather growth rates and steroid hormone concentrations in avian feathers
Brzobohatá, Tereza ; Albrecht, Tomáš (advisor) ; Sedláček, Ondřej (referee)
Avian life histories range along the axis from slow to fast, with slow life histories being characterized by greater investments in future reproduction, and fast by greater investments in current reproduction. The concept of pace-of-life syndromes refers to the coevolution of life strategies and related physiological, immunological and behavioral traits. Avian species from tropical areas are characterised by slower life histories (longer parental care, later maturation, smaller clutches, reduced metabolic rate) when compared to temperate zone species. Within this latitudinal gradient, investments in the total amount (weight) of body feathers have also been shown to be reduced in tropical birds. It remains unclear, however, whether feather growth itself follows this latitudinal pattern, and is slower in tropical species. Tropical birds have lower basal levels of corticosterone and testosterone, however available studies are based mainly on analyzes of hormone concentrations from plasma. The first aim of this diploma thesis was to evaluate differences between tropical (Cameroon) and temperate zone (the Czech Republic) passerine species in investments in tail feather growth by using methods of comparative ptilochronology. The second aim of the diploma thesis was to analyze concentrations of steroid...
The role of insect herbivory in plant population dynamics - a case study of the Lycaenidae family
Barusová, Anna ; Janovský, Zdeněk (advisor) ; Sedláček, Ondřej (referee)
Herbivory is one of the key interactions of plants, which can result in important consequences for their population dynamics and which can also exert selection pressure on evolution of their traits. This bachelor thesis is concerned with insect herbivore influence on plants at the levels of individuals and population dynamics. It also focuses on interactions of occurrence of herbivory with environmental conditions. This is demonstrated on the family Lycaenidae (Lepidoptera) which is highly specialized in terms of host plants with several cases of coevolution having been described. Some Lycaenid species also evolved associations with ants probably, which help to increase their range of host plants. The relationship of feeding strategies and myrmecophily is illustrated on Czech species of Lycaenidae. The last part focuses on the Great Burnet (Sanguisorba officinalis) and its European-wide declining monophagous herbivore Dusky Large Blue (Phengaris nausithous), their ecology and conservation. Ecology of this study system will be the main topic of the intended master thesis.

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1 Sedláček, Oldřich
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