The aim of the thesis was the appraisal of Great Crested Grebe (Podiceps cristatus) nesting biology aspects in relation to environmental conditions. The research took 6 months from the 2nd of April to the 2nd of October in 2013 and was realised in the Naděje fishpond system on the ponds Víra, Láska, Skutek, Dobrá Vůle, Rod and Naděje. This fishpond system is situated in CHKO Třeboňsko nearby villages Frahelž and Klec and it consists of total of 15 ponds which are used for intensive fish farming, partly for breeding of Wild Ducks for hunting purposes. The counting of birds, active searching of nests and measuring parameters of nests and eggs were carried out during the work. The nests were found on ponds Naděje, Skutek and Láska. In 2013 18 nests were measured altogether. On the fishpond Naděje 8 nests were situated, on the fishpond Láska 4 nests and on the fishpond Skutek 6 nests altogether. 13 nests of the total were found on a free water surface and 5 nests were situated in the vegetations of the Great Reedmace (Typha latifolia) at a maximum distance of 1 m from the free water surface. In 2013 64 eggs were measured altogether. On the fishpond Naděje parameters of 33 eggs were obtained, on the fishpond Láska 17 eggs and on the fishpond Skutek 14 eggs were found altogether.

The aim of the thesis was monitoring abundance and distribution of nests of Great Crested Grebe (Podiceps cristatus) during the season on the Naděje fishpond system. Further observation included factors that could affect nesting success of the Great Crested Grebe. Attention was concentrated on Wild Duck (Anas platyrhynchos) which is bred by man on the fishpond system and might negatively affect nesting success of Great Crested Grebe. Part of this study was the detailed observation of selected pairs during the nesting season by using camera traps. Temperature measurement in the nests was done by temperature data logger. The investigation was realized on the Naděje fishpond system near the village Frahelž. The research took place from the 14th of April to the 28th of October in 2015. In 2015 were found and investigated 37 nests on the Naděje fishpond system. On the fishpond Skutek were monitored 34 nest, on the fishpond Láska 2 nests and on the fishpond Rod only 1 nest. Majority nests (30) were found on a free surface and 7 nests were situated in the bushy vegetation. Parameters of 111 eggs were obtained altogether. On the fishpond Skutek were found 100 eggs, on fishpond Láska 8 eggs and in the only nest on fishpond Rod 3 eggs. Using the camera traps during the observation proved negative effect of wild duck on Great Crested Grebe nesting. The nest was destroyed group of wild duck. The maximum temperature in the nest reached 33,8 °C.

Piscivorous birds are an integrated part of lake and coastline ecosystems. Despite decades of research it is yet unclear what influence fish eating birds have on the fish community. The aim of this literature study was to focus on how two fish eating birds, Great Cormorant and Great Crested Grebe, influence the fish community in shallow and eutrophic lakes. Different types of analysis methods have been used when doing research on the subject, including pellet analysis, stomach content analysis, tagging of fishes by “PIT”-techniques and analysis by observation. Results show that conclusions by studies tend to vary, but generally higher bird density, lower water temperature and a relatively high turbidity contribute to a higher influence on the fish community. Both bird species are opportunistic in their choice of food and catch prey of the species that occur locally. Both species also limit themselves in the prey size, but the choice vary over seasons because of water temperature and the birds requirements in association with breeding and migration. The significant level of influence seems to be when predation is conducted on younger and smaller fishes. The influence on the fish size can also be indirect, where predation on smaller individuals prevent fishes from becoming older and bigger. As studies tend to deviate in conclusion, no general answer to this issue can be given at present. Comprehensive research with several years of full control over both fish-and bird population is needed to find the proper conclusion.

Piscivorous birds are often blamed for causing significant damage to fish stocks. Various methods are used to determine the composition of their food, each of them has limits in its ability to determine the complete food spectrum. This work maps the complete food composition of 14 species of fish-eating birds with a method that is not commonly used. Method used in this work uses analysis of publicly available photos on Google.com. In addition to the complete composition of the food, the species composition of the non-fish part of the prey was also determined, and in the case of the Great Cormorant (Phalacrocorax carbo), also the length of the fishes it catches. The aim of this work is to reveal the usability of this method for these purposes. A total of 2350 retrieved photographs were analyzed. The results obtained by photo analysis are in all cases compared with data in the available literature. For representatives of heron birds (Ardeidae), the analysis of photographs provided good information on the food spectrum of individual birds and on the qualitative composition of the non-fish component. It also provided relatively good information on the diet of the White-tailed Eagle (Haliaeetus albicilla), but the bird part of the prey was slightly underestimated. In the diet of the Great Crested Grebe...