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Migratory behaviour of Czech blackcaps (Sylvia atricapilla)
Valečková, Dominika ; Hořák, David (advisor) ; Procházka, Petr (referee)
Avian migratory behaviour has changed recently due to several factors including climate change. In many species of birds their wintering areas have become to move and their migratory paths have shortened. The Blackcap (Sylvia atricapilla), species with migratory divide located in the Czech Republic, established a new migratory path and a new wintering area on The British Isles within a few generations. This shorter route provides many benefits such as sooner return to breeding ground and occupying better territories, and lead to rapid growth of the number of individuals wintering there. Other changes in morphology (e.g. length of wings and bill, colouring etc.), ecology and ethology (e.g. earlier nesting accompanied by assortative mating etc.) are linked to this new migratory behaviour. The aim of this thesis is to analyse the ringing and mist netting data and compare the results with the published data, confirm existence of this migratory behaviour in our breeding population and obtain support of some related hypotheses. My results confirmed the existence of this new behaviour in our breeding population of blackcaps. During the period 1934-2020 Czech blackcaps changed their migratory behaviour in favour of a new route to The British Isles. Number of wintering blackcaps in these areas started to...
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Relationship between developmental rate and egg size in reptiles
Mrskočová, Jana ; Kratochvíl, Lukáš (advisor) ; Hořák, David (referee)
Existing analyses indicate that there is a positive relationship between egg mass and incubation period at large taxonomical scales. This suggests that animals are able to solve the trade-off between egg mass and developmental rate. However, some studies (not only reptile- focused) prove that this relationship is taxon-specific. Studies performed at the intraspecific level differ in the conclusion whether such relationship actually exists. Moreover, there are many factors which complicate these analyses (for example the ontogenetic shift at the time of oviposition, presence of diapause during the embryonic development, synchronization of the time of hatching, temperature and humidity). I suggest that the main factor is temperature that has been filtered out by various authors by means which I find unsatisfactory. This thesis attempts to prove that the relationship between egg mass and incubation period is not sufficiently and explicitly explained and to discuss the complications regarding its research.
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Incubation effort in Common Pochard and its determinants
Drekslerová, Šárka ; Hořák, David (advisor) ; Musil, Petr (referee)
Incubation of avian eggs is an energy demanding process. Incubating parent faces a conflict between investment into optimal thermal conditions for developig embryos and meeting of own energy requirements. This applies especially in uniparental incubators such as ducks. During incubation, female utilizes energy from fat storage or actual food intake. The proportion of energy used from food than may reflect the time spent by female on the nest. The utilizing of these both sources ratio plays a role in time spent on nest. The aim of the thesis was to describe an incubation rhythm in females of Common Pochard (Aythya ferina) and relate them to climatic variables and changes in body mass. Data were collecetd for three years in the Poodříí Landscape Protected Area at free-living females. We placed a weighting mechanism under the nest with conected datalogger recording voltage variations, which offered me an information about female body mass and time and duration of recesses. Incubation rhytm of females was described by time spent on time ("incubation constancy"), recess frequency and recess duration. Females left the nest most grequently at night-time and during dawn and dusk. Probable explanation of this pattern is better food availability in the night-time and lower risk of nest predation by predators...
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Drivers of avian diversity on an altitudinal gradient of Mount Cameroon
Djomo Nana, Eric ; Hořák, David (advisor) ; Šálek, Miroslav (referee) ; Waltert, Matthias (referee)
Altitudinal gradients constitute a powerful test system for understanding distribution of species around the globe. Tropical mountains are quite rich in species even after controlling for environmental productivity, and are ideally suited for studying patterns of species distributions because they have had sufficient time for species to produce a response to environmental changes that affect their life histories. In this thesis, I investigate basic ecological mechanisms potentially behind avian distribution patterns along an altitudinal gradient in West-Central Africa. I used data collected with four methodological approaches (point counts, mist netting, random walks and artificial nest experiments) along an altitudinal gradient on Mt. Cameroon from October 2011 to September 2013. This work is focused on two interrelated themes: selection pressures on life histories (Chapters 1, 2, 3 & 4), and avian assemblage structures (Chapters 5 & 6). In the General Introduction, I present an overview of the study area with conservation implications of the study and my study objectives. In Chapters 1, 2 & 3, I investigate how selection pressures, i.e., nest predation and parasitism by haematozoa, affect bird assemblages. I used artificial nest experiments to assess nest predation rates in Chapters 1 & 2, and my...
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Brood parasitism in Common Pochard - a proteomic analysis
Petrželková, Adéla ; Hořák, David (advisor) ; Piálková, Radka (referee)
Conspecific brood parasitism (CBP) is a situation, when female (a parasite) lays egg or eggs in a nest of other conspecific female (a host). Then she leaves the nest and doesn't provide any subsequent parental care, such incubation and care for young. To distinguish between parasitic and host egg or young could be difficult, because there are not obvious morphological differences. CBP was documented in more than 234 species and its frequency is different between species, but also between population of the same species. The main aim of my master thesis was to describe the degree of parasitism in two population of Common Pochard (Aythya ferina). The field work was carried out from 2004-2006 in Třeboň Biosphere Reserve and form 2008-2010 in Poodří Landscape Protected Area. We found that the degree of CBP is relatively high. In Třeboň was found 72 % (41) of parasitized nests and 32 % (165) of parasitic eggs and in Poodří 93 % (39) of parasitized nests and 37 % (153) of parasitic eggs. The mean number of eggs per clutch was around 9 and mean number of host eggs per clutch was 6 in Třeboň. The mean number of eggs per clutch in Poodří was about 10, and the mean number of host eggs was also about 6. The mean number of parasitic eggs per clutch was 3 resp. 4. It was also found, that parasitized nests are...
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Functional diversity in ecological communities
Džamba, Roman ; Hořák, David (advisor) ; Doležal, Jiří (referee)
Functional diversity is an important component of biodiversity. Value and range of functional traits and the number and composition of functional types are crucial for the short and long term functioning of ecosystems. Functional traits of species affect their performance in ecosystems and we can classify them as continuous or discontinuous. It has been suggested many ways to choose the appropriate traits and functional differences between species in estimating functional diversity. It is necessary to consider the nature and importance of ecosystem processes and environmental factors and consider properties of employed methodological approaches. There are many ways to estimate functional diversity. Functional diversity can be expressed by the number of functional groups, functional index or functional dendrograms. In natural communities, we see a positive relationship between species and functional diversity. Species diversity doesn't seem to be an adequate surrogate for functional diversity because the loss of an equal number of species may have different effects on the ecosystem, depending on the identity of the species. Functional redundancy refers to the functional similarity in the ecological niches occupation and is a source of stability in the ecosystem functioning.
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Influence of external conditions on egg incubation in lapwings (genus Vanellus) in temperate and subtropical climate
Pešková, Lucie ; Šálek, Miroslav (advisor) ; Hořák, David (referee)
During incubation, most birds require the presence of at least one parent to ensure suitable incubation conditions for embryo development. The main factors that affect the development of the embryo are temperature, humidity and egg turning. In this work, incubation conditions were investigated in two biparental Lapwing species (genus Vanellus), the Northern Lapwing (Vanellus vanellus), which faces the risk of egg cooling in temperate areas, and the Red-wattled Lapwing (Vanellus indicus), which faces the risk of egg overheating in the subtropics. A laboratory experiment testing the thermal properties of the Red-wattled Lapwing nest lining showed that it selects lining material that slows down temperature growth during egg heating, thus ensuring suitable thermal conditions during parental absence at high ambient temperatures. Temperature and egg turning during incubation were recorded by an artificial egg with a built-in sensors placed in the nests of both target species; data collected by the sensors were stored by a base-station located nearby. The average egg temperature was 32.5 řC for the Northern Lapwing, and 35.0 řC for the Red-wattled Lapwing. Egg temperature in both species fluctuated significantly, affected by many factors. Egg temperature increased with increasing ambient temperature, it...
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Hatching synchrony in birds
Tippeltová, Zuzana ; Hořák, David (advisor) ; Riegert, Jan (referee)
This bachelor thesis is about hatching synchrony in birds. Generally, among birds there are two types of hatching - asynchronous and synchronous- and the type of hatching is primarily determined by the time of the onset of incubation. In many bird species, including most precocial ones, incubation does not begin until the last egg has been laid, which results in hatching of all the eggs within a few hours. In synchronously-hatched broods, all the chicks are about the same age. Thus no single individual has an advantage in size or strength over any of its siblings in the nest. The survival probability is then similar for all chicks which maximizes number of fledglings under favourable condition. In contrast many species of birds begin to incubate as soon as the first eggs is laid and hatch their eggs asynchronously over a period of days or weeks, handicapping last-hatched chicks with an age and size disadvantage. Many hypotheses have been proposed to explain why female birds start to incubate before clutch completion and some of those suggest that asynchronous hatching is a parental strategy for raising the largest number of offspring that food resources will allow when the abundance of food for the chicks cannot be predicted at the time that eggs are laid. The selective pressures leading to the evolution of...
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The use of stable isotopes in the trophic ecology of birds
Rusnáková, Michaela ; Hořák, David (advisor) ; Procházka, Petr (referee)
Recently, the use of stable isotope analysis has been becoming increasingly common in ecological studies of animals. This interesting method is based on the premise that the isotope composition of consumer's tissues is related to the isotope composition of the sustenance consumed. This allows us to explore the contribution of individual food sources to the diet of species, populations or individuals, and at the same time to study their position in the trophic chains. The method enables us to research even omnivores, consuming variable food with different nutrients and isotope composition. Nevertheless, isotope values can differ depending on diet preferences, species physiology and the tissue type used for the analysis. This review summarizes current knowledge and results in the topic of stable isotope analysis, particularly in ornithological studies where the approach in question has been used to study the diet and trophic position. Powered by TCPDF (www.tcpdf.org)
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