Wildlife
Barbara Stalmachova & Jan Stalmach (from ”Olza - od pramene po ujście” : „Przyroda”, published by Region Silesia s.r.o. 2000) translated by D.French
The source and the upper course of the river.
The Olza is a river which emerges in the mountains where the current and turbulence define basic ecological processes. In the area around the source species of plants and animals typical for mountain springs in mixed, broadleaved and coniferous forests can be found. They are higher, vascular, shade-loving plants such as cress (Cardamine amara), golden saxifrage (Chrysosplenium alternifolium), loosestrife (Lysimachia nemorum) and others. Among trees growing around the Olza’s source are; sycamore (Acer pseudoplatanus), small-leaved lime (Tilia cordata), alder (Alnus glutinosa), grey alder (Alnus incana), sometimes beech (Fagus sylvatica), and less and less frequently fir (Abies alba). Among bushes are; red elder (Sambuctus racemosa), black honeysuckle (Locinera nigra) and bird cherry (Padus racemosa).
In the upper course of the river there is a strong current and a rocky riverbed. There are large stones in the river’s course, the current’s velocity is generally higher than 1 m/s, the water is cold and almost completely saturated with oxygen. In such conditions, only plants which can strongly attach themselves to the riverbed and resist such a strong current occur there, such as common water moss (Fontinalis antipyretica). This interesting water moss grows 40 cm long floating dark green growth. Green waterweed grows in some places, such as the gelatinous alga (Batrachospermum moniliforme), although it withstands the current weakly.
It ought to be mentioned that the number of species and amount of biomass of green plants is not particularly abundant in this part of the river. So where does the food chain begin? How does such a quantity of large insect larvae (aquatic insects, caddis flies and mayflies) nourish itself in this environment? Primary producers, i.e. green plants do not create the beginning of the food chain here – they have too extreme living conditions. Instead food enters from the outside in the form of organic waste at various stages of decomposition. The most important role in the food chain is played by bacteria in the upper course of the Olza, which break down organic detritus, releasing substances for other feeders. Bacteria play an irreplaceable role in the environment of the river’s upper course, decomposing organic substances and simultaneously producing bacterial protein, which is the basic food source for a great number of small creatures. The cold, swiftly flowing water highly saturated with oxygen guarantees that the rotting remains of organic substances do not gather in the upper course of the river. For this reason also fish from the upper course of the Olza are especially tasty.
The main inhabitant of this part of the river, and also the most striking is the river trout (Salmo trutta morpha furio), for which reason this part of the river has its own name; the trout strip. The trout reaches so far into the foothills, to where the water temperature never reaches 20°C and is relatively clean. The river trout is a cryophilic animal, which requires high oxygen saturation in water. The minnow, the miller’s thumb and Alpine bullhead also live in the same stretch of the Olza. In Poland two species of the genus Cottus exist, and both of them are protected species.
The most common aquatic invertebrate here is the crayfish (Astacus fluviatilis).
What do the banks of the upper course of the Olza look like? The large leaves of the butterbur (Petasites hybridus) and goat’s beard (Aruncus silvestris) are particularly striking.
Mountain meadows are charming and inviting, with their flowers, colours and scents. In spring the following flowers bloom in the meadows and margins of the riverine brush; wood anemone (Anemone nemorosa), lesser celandine (Ficaria verna), less often meadow rue (Thalictrum aquilegifolium), as well as marsh marigold (Caltha palustris) and vernalgrass (Anthoxanthum odoratum). Melandrium sylvestre blooms later with its red flowers, then in summer the cluster-head pink (Dianthus carthusianorum), and in drier and sunnier spots the fragrant wild thyme (Thymus serpyllum). Gentianopsis ciliate, a type of fringed gentian with blue flowers, which grows on the margins of broadleaved woodland is one of the rarer species. Another “Beskid” flower is the blue gentian Pneumonanthe asclepiadea, typical for mountain forests and meadows. The undergrowth by the river bank in the upper course of the river is typical for mountain riverside forests, classified by botanists as a community of alder forest with goat’s beard, alder (Alnus glutinosa), ash (Fraxinus excelsior), small-leaved lime (Tilia cordata), bird cherry (Padus racemosa) and pedunculate oak (Quercus robur). In the undergrowth there is the impressive false hellebore (Veratrum lobelianum), the yellow-flowering tuberous comfrey (Symphytum tuberosum), and the white flowered rue-leaved Isopyrum (Isopyrum thalictroides) growing to a height of between 10 and 30 cm. The protected coral-root is a frequent representative of Beskid flora and a typical Carpathian plant Hacquetia epipactis (with the Polish name of spring Cieszynianka). Coralroot (Dentaria gandulosa) is an endemic Carpathian plant growing in shady forests with a reddish-purple spray of flowers. Nine-leaved coral-wort (Dentaria enneaphyllos) is striking, with its pale yellow flowers. A rare fern – deer fern (Blechnum spicant) also grows in the undergrowth.
Many species of animal life live in the surrounding forests, meadows and riverine brush. Among the insect world several rare and unusual species of dragonfly from the order of Onata live around the Olza’s springs. The rare, protected golden ringed dragonfly (Cordulegaster boltoni) is worth seeing. It is a large dragon fly with a wingspan of 10.5 cm and a length of 9 cm. We can see various kinds of caddis flies (Trichoptera) near to the water. They usually fly short distances and alight on stones, tree stumps and the leaves of plants. They are often seen flying low over the water. Their larva live in water, probably everyone is capable of recognising them. However, it is difficult for the amateur to distinguish between different varieties of caddis fly.
Butterflies (Lepidoptera) are not only the most beautiful but also a varied order of insects. Around 2700 species of butterflies live in the region, although only 175 species are diurnal. For this reason only the species that are likely to be come across by the Olza will be mentioned. The orange tip (Anthocaris cardamines) is notable for its sexual dimorphism. Females are rather dull in colour while males can be identified from a distance, thanks to the large orange spots on their forewings. The red admiral (Vanessa atalanta), which can be seen on forest margins and in gardens, has pretty colouring. It occurs high up in the mountains, up to 2,000 m above sea level. The Arran brown (Erebia ligea), a mountain species occurring in damp meadows ought to be mentioned. It is one of the larger species, with black and white checks on the edges of its wings and a clear white spot on the undersides. A large number of hymenopterans live in the coniferous forests around the Olza’s springs. It is an order with an enormous number of species, with around 10 000 species living in Poland, which only represents a tenth of the number of species of hymenopterans in the world.
The colouring of the yellow-horned horntail (Urocerus gigas) resembles a large hornet. It is black with yellow stripes around 4 cm in length. It can be approached closely safely, as it does not have a sting. The other species of horntail is the Sirex juvencus.
Let us turn our attention to the vertebrates. We may meet the salamander (Salamandra salamandra) in damp places, particularly after rainfall or in the evening. It is a solitary creature and will try and run away if disturbed. The common frog (Rana temporaria) is the second most common amphibian in this area.
Reptiles are represented by two species here. If we are careful we may see a common lizard (Lacerta vivipara) basking in the sun, and higher up and nearer to the source the rare adder (Vipera berus).
Birds (Aves) exist in this region in much greater numbers and with a much wider range of species. Relatively large numbers of the greater spotted woodpecker (Dendrocopos major) live here. The rare white-backed woodpecker (Dendrocopos leucotos), which has a liking for old lichen on beech trees, lives and even nests here. The grey wagtail (Motacilla cinerea) can often be seen around irrigation ditches. Walking along mountain streams where water swiftly flows downhill among stones there is a good chance of seeing a dark bird the size of a thrush. It will be sitting alert on a boulder, twitching its short tail, sometimes giving a glimpse of its white underside. It suddenly dives into the water, suddenly to appear and fly swiftly away. It’s the dipper (Cinclus cinclus). The mistle thrush (Turdus viscivorus) is the largest bird of the thrush family. On first glance it can be confused with the song thrush, but the mistle thrush’s back is greyer, and its lighter underside is covered with more distinct, larger spots. Another bird which can occasionally be seen here is the ring ousel (Turdus torquatus). It’s of a similar size and colour to the blackbird but has a white crescent on its throat. Among the mammals living here are; the fox (Vulpes vulpes), badger (Meles meles), roe deer (Capreolus capreolus) and red deer (Cewus elaphus).
The middle and lower course of the Olza
The central section of the Olza’s course begins more or less between Bystřice nad Oląí and Vendrynĕ, the point at which the river leaves the mountain section of the Silesian-Moravian Beskid Mountains. The lower course of the Olza runs from Dĕtmarovice to the confluence with the Odra. Unfortunately again it won’t be possible to focus on all the animals that live on the Olza. Only rarer protected species will be mentioned or those that are particularly characteristic for the region. Among the invertebrates is above all the crayfish (Astacus fluviatilis) which can be found here from time to time. The very rare bladder snail (Physa acuta) also inhabits this part of the river.
Members of the mayfly (Ephemeroptera) order can be recognised by their three long, thin, threadlike “tails” at the end of the abdomen, short antennae and long forelegs. The rear pair of wings is much smaller than the forewings and some species don’t possess them at all. The larvae live in the water and adults usually remain close by. During warm summer evenings great swarms of mayflies can be seen flying up and down in formation over the surface of the water. Straight after being hatched adult mayflies mate and after the eggs have been laid, die. Most often seen are the common mayfly (Ephemera vulgate) and (Ephemera danica), which occurs here in large numbers. The most conspicuous insects to be seen flying above the water are dragonflies (Odonata). The fluttering flight of the dragonfly (Calopterix virgo), which has a wingspan of up to 7 cm, can most often be seen. The male is bright green-blue with greenish wings, while the female has transparent light brown wings. Access to the water is hindered by densely growing thistles, nettles and touch-me-not. The striking yellowish flowers of meadowsweet (Filipendula ulmaria) can be seen in places here.
The character of the river suggests that only the trout lives here, but there is also the European grayling (Thymallus thymallus), and dace (Leuciscus leuciscus); as well as other smaller fish like gudgeon (Gobio gobio) and the common loach (Noemacheilus barbatulus) which don’t overly interest anglers.
The river is a heaven for many species of bird. The most beautiful and striking is undoubtedly the kingfisher (Alcedo athis), often called the “flying jewel”. Its blue-green feathers flash like an azure spark, and it dives into the water after a fish like a burning meteorite. The colour of its plumage is constantly changing.
The dipper (Cinclus cinclus) has plain plumage; grey-brown with a bright white patch on its neck and breast. It hunts its food – mainly insect and crustacean larvae in a very interesting way, which is exceptional for songbirds. It dives to the river bottom helped by its wings and bill and prises off insects or looks for them under stones. When it emerges it is completely dry as water immediately runs off its oily feathers. In the lower sections of this part of the Olza’s course it can most often be seen in the winter. The grey wagtail (Motacilla cinerea) also hunts above the water. The little ringed plover (Charadrius dubius), Poland’s smallest mud bird, nests in places where sandbars are formed.
As far as mammals are concerned the occurrence of the otter (Lutra lutra) is interesting. Because it isn’t fussy about the quality of water in its hunting ground – it doesn’t bother the otter if it lives in mountain streams, rivers, large ponds or lakes – it can be concluded that the course of the Olza represents a migration route to other areas.