National Repository of Grey Literature 4 records found  Search took 0.01 seconds. 
Incubation behaviour of birds in polar regions
Hromádková, Tereza ; Pavel, Václav (advisor) ; Praus, Libor (referee)
The climate in the polar regions is so extreme that it has led to a big number of special adaptations in life and reproduction of local animals. However, the disadvantages are compensated by several important aspects like much lesser activity of preadtors, long sunny polar day and an abundance of nutriments during spring and summer. I tis no wonder that many species of birds have adapted their life cycle and migrate annualy thousands of kilometres to the polar regions in order to increase their chance of successfully leading out their offspring. Birds in these areas nest during the polar summer. Only one species of nesting begins already during the polar winter, i tis an Emperor Penguin (Aptenodytes forsteri) in Antarctica. The broods of birds nesting in polar regions are bigger in quantity in average and they also incubated longer then their conterparts in temperate and tropical. The main difference is the incubation rhythm adjusting mainly the extension of sessions associated with a reduction of recesses. The only exception are songbirds who leaves their nests frequently but only for a short periods of time. The information about the incubation behaviour of the most of the bird species of the polar regions are still very limited and incomplete. Therefore, bachelor thesis contains so far...
Role of microorganisms in the evolution of reproductive strategies in birds
Novotná, Lucie ; Javůrková, Veronika (advisor) ; Ferenc, Michal (referee)
Microorganisms are ubiquitous and can be found on the body of birds, in avian nests or may be carried into the nest along with nest-lining material. Microorganisms may therefore colonize eggshells of eggs in a clutch and subsequently penetrate into the egg contents. This so called trans-shell infection has been observed to affect hatching success, cause embryo mortality or subsequently influence hatchlings phenotype. Nevertheless, the probability of eggshell bacterial load or trans-shell infection depends on many factors, including environmental conditions, nest type, incubation pattern, and nest-lining material. Furthermore, some modifications of avian reproductive strategies may lead to reduction of negative effect of trans-shell infections, and significantly improve reproductive success. These mechanisms include incubation, mechanical and chemical barriers of egg, eggshell pigments or using of feathers and specific plants as nest lining material. Based on these findings, it can be concluded that the different reproductive strategies in birds should be a result of strong selective pressure caused by microorganisms. Although many recent studies have supported this assumption, research on this issue still suffers from many methodological shortcomings that must be eliminated in future studies.
Investment in reproduction and nest defense in waterfowl
Javůrková, Veronika ; Albrecht, Tomáš (advisor) ; Remeš, Vladimír (referee) ; Weidinger, Karel (referee)
Investment in reproduction is considered to be crucial component of life history traits. Reproductive success is however constrained by generally unpredictable environmental conditions. Based on "bet hedging" theory, individuals are forced to eliminate such unpredictability via the mixed strategy to maximize their long-term fitness. Predation represents underlying factor affecting individual reproductive success, and it undoubtedly lies behind the evolution of alternative reproductive strategies such as extra-pair paternity and conspecific brood parasitism. Behavioral mechanisms related to nest defense are thought to be investment in reproduction in accordance with trade-off between actual and residual reproductive value. Despite the extensive interest in the principles associated with parental investment into the nest defense, studies describing in detail the pattern of particular antipredator strategies are rare. Similarly, mechanisms responsible for maintenance of egg- viability during prolonged egg-laying period in species delayed the onset of incubation are poorly understood. In accordance with mentioned themes, this thesis includes publications aimed at aspects of reproductive biology and antipredator behavior in Mallards (Anas platyrhynchos). Particular publications concretely documented: a)...
Incubation strategies of selected duck species
Klvaňa, Petr ; Albrecht, Tomáš (advisor) ; Šálek, Miroslav (referee) ; Bureš, Stanislav (referee)
- 9 - Incubation strategies of selected duck species Summary of the PhD. thesis Avian incubation is an energetically demanding process. It holds true especially for uniparental incubators in which all incubation efforts are restricted to one individual. All ducks species breeding in northern hemisphere are representatives of birds with uniparental care. High demands of clutch formation and incubation make from ducks perfect model for testing factors influencing parent investment decisions. On the other hand parental investment to actual breeding attempt depends on many factors including breeding season duration, food supply, female's age, risk of predation or resilt of previous nesting attempt. So investigation of this complex problematic is extremely difficult. This thesis is focused on the most important phase of breeding cycle - incubation of clutch. Clutch incubation is associated with high energy cost to maintenance optimal temperature conditions for developing embryos. Morover incubation process can has large effect on female's body mass because of reduction of feeding time. Incubation strategy of success female include many partial tactic reducing predation risk of clutch and incubating female or eggs cooling. The incubation strategies of three ducks species were investigated in this thesis - Mallard...

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