Eesti Loodus 2013/06-07

 Summary

The world as a bird sees it

Tuul Sepp and Lauri Saks discuss over how birds might see the world and if their sight different from ours. Abundant, but very complicated studies have shown that many bird species’ perception is sensitive to ultraviolet light. Such species include passerines, but also gulls, nandus and parrots. Other bird species are able to sense violet light. Better vision helps birds to receive more signals from the environment and therefore birds are very dependent on their sight, rather than on hearing or smelling. It has been speculated that UV-ornaments pose a secret way of communication among passerines, as mammals and birds of prey cannot detect these. So, birds sense the world in a very different way that we, the humans. Therefore, many conclusions about behaviour or the colour of plumage can easily prove wrong.

 

The status of pike-perch fry in our large lakes

Kai Ginter and Külli Kangur observe the changes in the numerousness of pike-perch, an important predatory and game fish: why has the species become less abundant in recent years in lakes Peipsi and Võrtsjärv?  The question is important as environmental conditions seem to be favourable for the species. However, the size and strength of a pike-perch population are largely dependent on the availability of food for the larval and juvenile stages of the species. Studies reveal that the number of lake (dwarf) smelt, the first prey fish for the pike-perch has decreased considerably, as has the abundance of zooplankton. Due to climate change the transition from diet involving zooplankto to diet involving fish happens later in the development of a pike-perch and that has weakend the whole population.

 

Confusion over the birth date and place of Otto von Kotzebue

Vello Paatsi attempts to clarify the defects in the biography of the famous seafarer born in Estonia. The confusion remains, but the author suggests to stay with the date December 19 (old calendar) / December 30 (new calendar) 1787, and most probably he was born in Tallinn.

 

Beneficial bugs in fruit garden

Külli Hiiemäe introduces tiny animals who help the gardeners in disinfestation: generally, bugs tend to be useful rather than harmful. Beneficial bugs are enemies of the pests: beasts of prey, such as beetles, or parasitoids from the order of Hymenoptera. The most common families include ground beetles, ladybugs, rove beetles, soldier beetles, several species of Heteroptera, Chrysopidae, hoverflies, gall midges and earwigs. The author introduces the little helpers from all these families and orders.

 

Bugs that harass apple trees

Luule Metspalu takes a glance at small bugs, which can bring a lot of trouble to a gardener. The most common enemy is the codling moth (Cydia pomonella), the common apple maggot. Another species feeding on apple fruits is apple fruit moth (Argyresthia conjugella). Many more species yield a loss to apple buds, blooms and leaves, the most noteworthy of these being the  Apple Ermine (Yponomeuta malinellus). Numerous species of the family of Tortricidae also bring harm to leaves, blooms, buds and fruits. Young sprouts and leaves are damages by different species of aphids. All these, and many other species and their ways of life are described in the article.

 

A beetle desired by Darwin

Enno Merivee and Anne Must look back on the passionate meeting of Charles Darwin and the crucifix ground beetle, Panagaeus cruxmajor, a very rare beetle in Great Britain.

 

The karst lakes of Taebla

Tõnu Ploompuu describes little- known natural phenomena in the surroundings of Taebla, the Lääne County, where a nature protection area is soon to be created. Karst lakes are considered as very valuable communities according to the EU nature directive, but are regarded as pointless large puddles with little value. There are numerous karst lakes forming a whole system near Taebla. The plant cover of the spring lakes is diversified, varying from species-rich meadowland to eutrophic fens, partly covered with forest.

 

Interview: Nature conservation has a hopeful future

Toomas Kukk has interviewed Keit Pentus-Rosimannus, the minister of environment of Estonia.

 

When to plant potatoes or a little bit of date magic

Mait Sepp and Triin Saue give advice on when is the right time to plant potatoes in order to get a good yield. The soil has to be warm and dry enough, but still a bit moist. The authors introduce a production process model POMOD, which is based on the principle of maximum yield. But the generated statistics does not really help in finding the best date for planting. To conclude, it makes the most sense to observe the weather and feel the soil to reach the best decision.

 

Estonian Nature enquires

Riho Kinks explain why the subscribers of our magazine receive a number of “Tiirutaja”.

Ants Talioja introduces the activities of Tuhala nature center.

 

The traces of agriculture and cattle-breeding in landscape

Lembitu Tarang, Triin Kusmin and Jürgen Kusmin recommend finding traces of cultural heritage that are hard to notice and mostly located a bit away from farm landscape. Examples of such traces include signs of former melioration, silos, hay sheds, wooded meadows, dry-stone walls, wells and springs.

 

Tree of the Year: Guelder rose in folk tradition

Marju Kõivupuu calls up on the wisdom and knowledge of Estonians and neighbouring nations related to the tree of the year, the guelder rose, a rather little known bush. It has mostly been used as a medicinal herb. Mostly the tree bark, but also blooms and young sprouts have been used to cure many different diseases. The berries have been eaten less, as it was they were often considered poisonous. The guelder rose has much more importance in Russia and among other Slavic nations, such as Ukraine.

 

A parcel taken by the sea

Maili Roio has been studying the wreck of a cargo ship, which found its end on a mine and was found last year from near the Hiiumaa Island. The steamer called “E. Russ” was loaded at the port of Bordeaux, and reached the Tahkuna peninsula on September 15, 1919, hitting a mine. The crew and 8 passengers survived, but the drown cargo, including about 50 cars, was a huge loss to the new country.

 

A different Finland – a land of oaks and limestone cliffs

Tapio Vares takes the reader to a different Finland, to the Lohjansaari area. The lovely nature of the area is quite similar to ours. While Finland in general is covered with birch trees, the broad-leaved forests dominate in the Lohjansaari area.

 

Gonyostomum semen is seen in summer

Aimar Rakko knows the answer to the question why we can become covered with a layer of mucus while swimming in a seemingly clear-water lake. The species causes algal blooms and shakes the natural balance of a lake ecosystem. When the algae cell becomes into contact with a human, it shoots a squirt of mucus from its vesicles. The species prefer soft-water lakes and shows the trend of increasing its spread throughout the Nordic countries.