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Functions of a female song in passerines
Kubíková, Tereza ; Petrusková, Tereza (advisor) ; Mikula, Peter (referee)
Female song in passerines was overlooked for a long time because it was assumed that only males sang, even though the first records of female singing appeared at the end of the 19th century. The sporadic singing of females was usually explained by an increase in the level of sex hormone but in reality, females probably sing for the same reasons as males, i.e. to defend their territory, attract a mate, or prevent extra-pair copulation. These functions of female song were discovered when ornithologists began to focus more on tropical songbirds. In fact, in the tropics, many species show sexual dimorphism, making distinguishing females from males easier. Partners also make long-term partnerships and they usually defend year-round territories together so it is advantageous for them to be synchronized in their songs too. For this reason, females sometimes join their partners in singing to make duets. Today, the female song has been recorded in many temperate songbirds and the number of species is gradually increasing but it is probably still overlooked in many species because females can be mistaken for males or because they sing only for short periods of time so it can be more difficult to capture their song. Keywords: female song, birds, function of female song, temperate zone
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Species-area relationship in birds: variation across temperate zone environments
Gaigr, Matěj ; Hořák, David (advisor) ; Hanzelka, Jan (referee)
The relationship between area and number of species is one of the oldest and most studied principles in ecology, often referred to as one of the laws of ecology. Ecologists use it primarily to model the expected number of species in a given area. The Species-Area Relationship (SAR) states that the larger the area being, the greater the number of species present. However, area is not the only factor influencing species diversity - habitat heterogeneity is also a frequently studied factor affecting species richness. The number of species in an area tends to be positively influenced by heterogeneity since factors that are positively correlated with heterogeneity have a large influence. These factors include the species diversity of vegetation, the level of energy productivity, the number of microhabitats, the effect of disturbance or the amount of different food sources. Individual temperate habitats differ in the relative contribution of heterogeneity in its impact on observed species abundance. Species abundance is not only influenced by habitat heterogeneity, but also by other factors such as altitude, climate or latitude. The most affected habitats regarding the relative contribution of heterogenity are forest environments. Vertical diversity is the main influence causing high heterogeneity in...
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Problematika zvětrávání hornin ve vztahu k vývoji půd a možnostem lesnictví v rozdílných klimatických pásmech Asie
Krejčíř, David
The bachelor thesis objective is to give a comprehensive view of rock weathering issues in relation to soil development in tropical, subtropical, temperate, cold climate and forestry options in the different climatic areas in Asia. The result is not only pure background research composed of comprehensive summary of weathering issues with pedogenesis, but its implementation to particular areas covered by the authors practical observation from the north to the south of Asia, more specifically from the tundra and the boreal coniferous forest of Siberia up to the equatorial and its local tropical rainforest ecosystems. The reader will not only get a clear overview of changes in vegetation, weathering types and their mutual relation in local and global scale, but will also gain understanding of main climate and erosion impacts on different climatic zones and their processes. This bachelor thesis focuses on erosion development, degradation of landscape by influence of anthropogenic and natural activities, and actual forestry issues in Siberia, Mongolia and in China.
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