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.