Vpliv košnje na številčnost repaljščice (Saxicola rubetra) na Ljubljanskem barju

Lenarčič, David (author), Tome, Davorin (mentor)

Številčnost ptic kmetijske krajine v Evropi upada zaradi več razlogov, med drugim uporabe pesticidov in globalnega segrevanja. Najpomembnejši vzrok je verjetno intenzifikacija kmetijstva, predvsem košnja travnikov, ki povzroča smrtnost osebkov neposredno ali pa posredno zaradi zmanjšanja dostopnosti in pestrosti hrane. Enako velja za repaljščico (Saxicola rubetra), ki je pomemben indikator stanja ekstenzivnih travišč, ki se pojavljajo tudi na Ljubljanskem barju. Da bi preverili vpliv sprememb v režimu košnje na repaljščico, smo v letih 2002–2018 na sklopu travnikov na jugozahodnem delu Ljubljanskega barja popisovali repaljščice in njihova gnezda s kartirno metodo in obenem kartirali potek košnje. Ugotovili smo, da se datum začetka košnje v tem obdobju ni premaknil bolj zgodaj v sezono, medtem ko je bil datum, ko je bilo 10 % in 50 % površin pokošenih, vedno bolj zgodaj. Spremembe niso bile ozko linearne. Tudi v obdobju, ko je bilo na košnjo občutljivih zadnjih 50 % repaljščic, je bilo z leti pokošenih vedno več površin. Iz teh rezultatov vidimo, da je košnja v raziskovanem obdobju potekala vedno hitreje. V obdobju raziskave je vsako leto propadel večji odstotek gnezd. Ugotovili smo tudi, da je več gnezd propadlo v letih, ko je bilo 10 % in 50 % travnikov pokošenih bolj zgodaj. Padavine so bolj zamaknile začetek košnje kot začetek gnezdenja. Čeprav je večina pokazateljev vpliva košnje na gnezditveni uspeh v naši nalogi posrednih, ocenjujemo, da spremembe v režimu košnje negativno vplivajo na številčnost repaljščic.

• Language: Slovenian
• Keywords: intenzifikacija kmetijstva, travniške ptice, košnja, repaljščica, Saxicola rubetra
• Work type: Master's thesis/paper
• Organization: BF - Biotechnical Faculty
• Year: 2019
• PID: 20.500.12556/RUL-109788
• COBISS.SI-ID: 5331791
• Publication date in RUL: 08.09.2019

Secondary language

• Language: English
• Title: The Effect of Mowing on the Abundance of the Whinchat (Saxicola rubetra) on Ljubljana Marsh.

Abstract

The numbers of grassland birds are declining due to several reasons, like the use of pesticides and global warming. The most important reason for that is probably agricultural intensification, predominantly mowing, which directly causes bird mortality and indirectly lowers the availability and diversity of food. The same goes for the whinchat (Saxicola rubetra), which is an important indicator of extensively managed grasslands which also appear on Ljubljana Marsh. To determine the influence of changes in the mowing regime on the local Whinchat population, we mapped mown surfaces and whinchat territories. We found that mowing did not start earlier each year. However, the dates when the 10 % and 50 % of the surface was mown, happened increasingly earlier. The changes we've measured were not strictly linear. In the period when the last half of whinchats was susceptible to death by mowing, the percentage of mown surfaces increased through the years. These results show that mowing started becoming increasingly faster. The percentage of nests failed due to mowing also increased through the years. An earlier onset of the day, when 10 % or 50 % of surfaces were mown, also caused greater nest mortality due to mowing. Rainfall delayed mowing more than nesting. Even though most of our indicators of the effects of mowing are indirect, we are estimating that the changes in them are negatively impating the numbers of whinchats on Ljubljana Marsh.

• Keywords: agricultural intensification, grassland birds, mowing, whinchat, Saxicola rubetra