|
|
Analysis of photo-records of non-fish prey in the diet of selected species of fish-eating birds
Mach, Jakub ; Čech, Martin (advisor) ; Vejřík, Lukáš (referee)
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...
|
|
|
The nest parameters od Great Crest Grebe (Podiceps cristatus) in Naděje pond system in the Třeboňsko Landscape Protected Area
ALT, Miroslav
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).
|
guest ::
