|
| |
|
|
Morphological variation of Cameroonian sunbirds
Bovšková, Denisa ; Hořák, David (advisor) ; Chmelová, Eliška (referee)
5 Abstract Morphological traits give information about the adaptations of the studied species, the resources, which it uses, and they can generally tell us about the use of ecological space. Intraspecific morphological variability reflects various adaptations of local populations thus variability reflect different way of life. The subject of this thesis is an ecologically interesting group of specialized tropical songbirds - Sunbirds (Nectarinidae). The taxon exhibits number of adaptations to specific food collecting a combination of nectarivory and insect hunting. I focused here on the intraspecific variability of three species (Cyanomitra oritis, Cinnyris reichenowi and C. bouwieri) living in different habitats in Cameroon. The aim of this work was to find out in what morphological characters are this species sexually dimorphic. Furthermore, if their populations living in remote locations differ? Finally, if all studied species show similar trend of intraspecific variability of the traits, which could have common ecological causes. The following traits were measured: wing and tail feather length, beak dimensions, total body weight and other characters. The analysis is based on field data collected between 2003 and 2015 and museum collections. Overall, we collect information about ca. 1200 individuals for...
|
|
|
Conspecific brood parasitism: a case study on the common pochard and the barn swallow
Petrželková, Adéla ; Hořák, David (advisor) ; Musil, Petr (referee) ; Guillemain, Matthieu (referee)
Presented thesis is mainly concerned with the conspecific brood parasitism (CBP) in birds. CBP is an alternative reproductive strategy when a parasitic female lay egg or eggs to other (host) female's nest of the same species. Then the parasitic female leaves the host's nest and does not provide any energetic investment in a subsequent parental care. Distinguish parasitic eggs or young is problematic because there are no obvious morphological differences. Thus, the use of molecular method is crucial for proper determination of CBP. CBP can be used as 'a best-of-bad-job' when female does not have her own nest or lost her nest for example through predation. Other option is that female can increase her fecundity ('fecundity enhancement' hypothesis) when she lay parasitic egg/eggs and care about her own clutch afterward. Two different model species were studied. The first one was a precocial diving duck - the common pochard (Aythya ferina; Anseriformes; Anatidae). Protein fingerprinting was used for detection of CBP and for distinguishing between eggs of individual females. It was found that the rate of CBP was relatively high in this species (91%, 72%; Chapter 1, 4). Further results indicated that the host clutch size decreased with the number of parasitic eggs in the clutch. The study of individual...
|
|
|
Influence of incubation temperature on avian embryo development
Pešková, Lucie ; Šálek, Miroslav (advisor) ; Hořák, David (referee)
Avian incubation is influenced by three basic factors: temperature, humidity, and egg rotation. The incubation temperature can significantly affect the development of an individual before hatching as well as after it. In natural conditions the incubation temperature is maintained by a parent trying to stabilize it at the developmental optimum. The parents must also provide their own needs during incubation, which results in temperature fluctuations. Although the incubation temperature is species-specific, its mean varies between 30 řC and 40 řC across all avian taxa. Lower temperatures but still within the optimum range cause reduced hatchability and prolongation of incubation period. Higher temperatures within the optimum range shorten incubation period and also reduce hatchability. Incubation temperature affects also the weight of an individual, its body proportions, metabolism, survival after hatching, and possibly also reproduction success (fitness). A detailed understanding of the mechanisms by which temperature affects the embryo development and its features is necessary, among others, to optimize incubation methods in artificial incubators. Key words: incubation, temperature, reintroduction, egg, avian embryo, hatchability, incubation length
|
|
|
Size and stability of territories in tropical birds
Charvátová, Barbora ; Hořák, David (advisor) ; Lučan, Radek (referee)
The size and the stability of avian territories are at first sight quite different in the tropics if compared to the temperate zone. Territories of tropical birds are relatively more stable in time and space. Their owners defend territories year-round, between years and the boundaries of territories remain unchanged. Tropical territories are also many times larger in size. These specific properties are conditioned by many interconnected factors. The size of the owner and food availability have a significant influence. The size of the territory increases with the size of the owner. And the owner reduces territory size with a higher food supply. It is food availability, which is closely related to the quality of the environment. Generally, the density of individuals is lower in lower quality areas. Thus, owners adapt their territories - increase size. This is especially interesting in the tropics, considering that there is much higher species richness and lower population density than in the temperate area. Differences in territory can also occur due to different altitudes - there are larger territories in tropical montane cloud forest. Also, the location in the area and potential barriers have influence, but rather in position than in a size. Studying these factors explains the differences in...
|
|
|
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)
|
|
|
Bird communities in stands of non-native trees
Hanzelka, Jan ; Reif, Jiří (advisor) ; Hořák, David (referee) ; Šálek, Miroslav (referee)
6 Abstract This thesis deals with the effects of non-native tree stands on birds in the Czech Republic. Non-native plants, including trees, are known to adversely affect the biodiversity. At the same time, birds represent a widely used biodiversity indicator. The studies of bird communities in stands of non-native trees presented here show the extent to which the birds have been impacted by non-native tree stands. This knowledge can be used to evaluate the importance of non-native plants as a biodiversity threatening factor. As the representatives of widespread non-native trees, the broad-leaved black locust and coniferous black pine were selected. In these stands I investigated possible mechanisms affecting bird communities, arising from assumed differences in vegetation structure, bird species richness, bird community composition, food supplies, and nest predation pressure compared to the stands of native oak and native Scots pine. In general, the bird species richness positively correlates with the vegetation structure complexity. Despite the fact that the non-native stands proved to have a higher heterogeneity of vegetation structure than the native stands, bird species richness did not differ among the focal stands. The bird community composition was primarily affected by the birds' preference of...
|
|
|
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...
|
|
|
Effect of habitat fragmentation on bat ecology
Kočí, Jakub ; Lučan, Radek (advisor) ; Hořák, David (referee)
Habitat fragmentation poses one of main threats to biodiversity. Bats (Chiroptera) serve as an important group of bioindicators. Habitat disturbance can induce different answers among them, especially in a tropical forest where bats provide important ecosystem functions such as seed dispersal and plant pollination. Difference between their reactions can be seen between different biomes: Negative influence to the species richness can be expected in a tropical forest with high degree of endemism whereas in temperate zone with long-term human influence to the landscape composition bats might have partially adapted to patchiness of the landscape and fragmentation could have locally positive effect. This thesis aims to summarize current knowledge of how fragmentation influences bat ecology with special aim for the difference between various biomes. Key words: Bats, Chiroptera, fragmentation, neotropics, paleotropics, Europe, temperate zone
|
|
|
Metabolic costs of reproduction in vertebrates, particularly in reptiles
Kukačková, Dominika ; Kratochvíl, Lukáš (advisor) ; Hořák, David (referee)
Animal reproduction involves energy expenditures for gamete formation, support of offspring development, and associated behavioural changes. Due to high variability in reproductive traits, reptiles are the ideal study group for this field. Investment in reproductive organs and gametes represent costs of sex products production. The next phase of reproduction is gestation, when females support their developing offspring, which results in additional metabolic costs. Metabolism of pregnant female can be viewed as a sum of resting metabolism, which is the same as in non-pregnant animal, of increased metabolism to support pregnancy, and of embryonic metabolism. Separation of each component is crucial for assessing energy costs of reproduction and for comparison of different reproductive strategies. Certain behavioural changes during reproduction can influence total energy balance as well. These changes include increased locomotion costs or shifts in the thermoregulatory behaviour. Estimation of the real costs of reproduction is a complex matter since a reproduction is a very dynamic process and there are many issues that influence the overall energy consumption of reproducing individuals.
|
guest ::
RSS feed.