Třeboňsko also has an exceptionally rich fauna and there are few areas of equivalent size where we can find as many taxons as we can here. This species diversity is a result of the great diversity of habitat types - from peatbogs as glacial relict biotopes on the one hand to various types of wetlands, forests, alluvial plains and meadows to extremely dry localities with a range of thermophilous species on the other. The diversity of localities is especially reflected in the communities of invertebrates, which are much more tightly bound to specific microclimates, vegetation and soil types than are the vertebrates. Another factor determining the Třeboňsko fauna composition is the region’s most important landscape feature, the fishponds. These artificial wetlands of various types have been settled over the centuries by a large number of new species of which waterbirds are the most noticeable. At present the fishponds are among the most valuable localities in central Europe regarding their animal communities, despite the intensity of fish-farming methods used on them. The third and final factor determining the area’s richness of fauna are the extensive forest complexes. Even though most of the forests are commercially planted and have a non-natural species composition, they provide a refuge for a large number of vertebrate species which are rare or extinct in the neighbouring regions.
Typical inhabitants of extremely dry sandy localities are certain kinds of hymenoptera, including digger wasps, solitary bees and spider-hunting wasps. On the air-blown sands the grasshopper Oedipoda caerulescens is commonly found. A range of interesting and exceptional thermophilous species are bound to warmer localities with deciduous trees (especially old oaks on the fishpond dam walls and in the remnants of alluvial forest). These include great capricorn beetle (Cerambyx cerdo) and the beetle Osmoderma eremita. Very valuable invertebrate communities are bound to the various types of wetland ecosystems on the alluvial plains of the rivers, the fishponds and other man-made water surfaces such as the flooded sand or gravel pits, or water-filled depressions left behind after peat extraction. Although these biotopes harbour a range of valuable species, their greatest significance is the quantity of ‘ordinary’ species that they support, many of which are disappearing in the surrounding regions which have been drained and dried out. These are predominantly species of molluscs, crustaceans, spiders, dragonflies, stoneflies, alderflies, caddis flies, etc. A large population of hungarian glider butterfly (Neptis rivularis) in the Czech Republic can only be found in the Třeboň basin as it is bound to the widespread stands of willowleaf meadowsweet (Spiraea salicifolia). The invertebrate community bound to the area’s peatbogs is of great value and we can find many glacial relicts, species which have survived here since the Ice Ages.
Fish, Amphibians and Reptiles
The most notable and valuable fish species in the area are the brook lamprey (Lampetra planeri) which still breed in some of the cleaner sections of rivers and streams, burbot (Lota lota), spined loach (Cobitis taenia) and bullhead (Cottus gobio). A strong population of weatherfish (Misgurnus fossilis) inhabits pools in the Nová řeka marshes and on the floodplains of the Lužnice to the south of the junction with the Stará řeka canal and Nová řeka canal. The most valuable among the area’s 15 amphibian species are natterjack toad (Bufo calamita), which mostly breeds in periodic pools near thesand pits, and great crested newt (Triturus cristatus). During the 1990s, the populations of most amphibians increased and the same is true for most reptile species. The viviparous lizard (Lacerta vivipara) and common viper (Vipera berus) typically inhabit forest clearings and peat bogs. In total, 6 reptile species live in the area.
Birds and Mammals
Nearly 280 species of birds, at least 182 of which regularly nest here, have been recorded within the territory of Třeboňsko PLA. The great concentration of fishponds, flowing water and marshes makes the Třeboňsko one of the most important localities for water and wetland birds in central Europe. In some years, up to 20,000 migrating birds can be seen resting on the surface of the fishponds, especially during the autumn. A nesting colony of cormorants (Phalacrocorax carbo) has existed in the area since the early 1980s and now numbers about 200 pairs. Members of the heron family which nest in the area include night heron (Nycticorax nycticorax), the grey heron (Ardea cinerea) being common. The population of great white egret (Egretta alba) is increasing. The Velký Tisý and Horusický fishponds are a summer gathering ground for greylag goose (Anser anser), the population of which exceeds 10,000 individuals. The most significant nesting ducks are around 50 pairs of goldeneye (Bucephala clangula) and more than 40 pairs of red-breasted pochard (Netta rufina). More than 10 pairs of white-tailed eagle (Haliaeetus albicilla) successfully nest in the area, which is one of the most important populations in central Europe. The wintering population of eagles numbers several tens of individuals. Approximately 50 pairs of marsh harrier (Circus aeruginosus) nest in the reedbeds around the fishponds.
The Třeboňsko is used as a migration stop-over by many species of waders, that we can find, during the migration period, on the bottom of drained fishponds. However, only a few wading species nest here. One of the most common water birds in the area is the black-headed gull (Larus ridibundus), although the population has decreased in recent years. Presently around 100 pairs of common tern (Sterna hirundo) make their nests here, especially on artificial sandy islets or sandbars in the ponds. Eight owl species live and nest in the Třeboňsko PLA, including pygmy owl (Glaucidium passerinum), Tengmalm’s owl (Aegolius funereus) and eagle owl (Bubo bubo). The nightjar (Caprimulgus europaeus) is typically found around peatbogs or in large forest clearings. Around 20 pairs of kingfisher (Alcedo atthis) live around the region’s rivers and streams. The black woodpecker (Dryocopos martius) is common in older forest stands andmiddle spotted woodpecker (Dendrocopos medius) can be seen in the floodplain forests and on the tree-lined dams of fishponds. Seven members of the woodpecker family nest in the area. Characteristic songbirds for the region are especially those species bound to wetlands, including Savi’s warbler (Locustella luscinioides), bearded tit (Panurus biarmicus), reed warblers and the bluethroat (Luscinia svecica). Approximately 50 species of mammals have been recorded in the Třeboňsko PLA, the most valuable of which is a prosperous population of otter (Lutra lutra), numbering 150 to 200 individuals, which makes it one of the largest and most stable populations in central Europe.