The nest parameters od Great Crest Grebe (Podiceps cristatus) in Naděje pond system in the Třeboňsko Landscape Protected Area

The main objectives of this study were to control and analyse the chosen aspects of the nest biology of the species known as the crested grebe (Podiceps cristatus), to set an amount of nesting population and its distribution during the season in the Naděje fishpond system (further NRS), to estimate the adaptibility of this species on the conditions of the intensive cultivated fishponds in the NFS. The Naděje fishpond system is situated in the Třeboň basin, approximately 8,5 km to the south of the town Veselí nad Lužnicí, between the villages Frahelž and Klec. The above sea level is about 410 meters above the sea there. The axis of the whole fishpond system is the River Lužnice. This system is created by 15 close together neighbouring fishponds. These fishponds are used for fish breeding of especially common carp. This study has been made in the observed area in year 2009. In regular intervals there game census of the Great Crested Grebe (Podiceps cristatus) has been done and at the same time on the same fishponds there other species of water birds have also been counted in order to gain the survey of bird population. The measured values have been statistically processed. In 2009, the highest number of adult and juvenile Great Crested Grebes was recorded 8 August for the Skutek Pond (44 adult individuals and 23 juveniles), 6 September for the Láska Pond (25 adults and 40 juveniles) and 2 July for the Víra Pond (15 adults and 10 juveniles). The most numerous aquatic bird species were Anas platyrhynchos, Anas strepera, Fulica atra, Larus ridibundus and Podiceps cristatus. The Great Crested Grebe have been prefered especially the fishponds Láska, Skutek and Víra, in the other watched fishponds they have appeared very small or not at all. In this three fishponds there the straight search of the nests connected with a measurement of egg parameters have been done. There have been found altogether 46 nests with 170 eggs. 23 nests have been situated in the vegetations of the great reedmace (Typha latifolia) and 23 nests in the lesser reedmace (Typha angustifolia)