Wildfires can be the most influential phenomena in landscape dynamics and play an important role in determining avian populations. However, the intentional burning of habitats is still a controversial management practice and is legally prohibited in many countries. On the other hand, fires can positively control, or even slow down vegetation succession of reeds and bushes, and, in particular cases, may sustain a habitat for open marsh nesting specialists. One such species is the Aquatic Warbler Acrocephalus paludicola, a globally threatened habitat specialist that breeds in open fens in Central and Eastern Europe. Because bush and reed encroachment threaten many suitable breeding areas, habitat management is necessary to maintain the open wetlands that Aquatic Warblers require for nesting. To assess whether burning was beneficial, we analysed Aquatic Warbler numbers and distribution in the Chelm calcareous marshes in eastern Poland on plots in different successional stages after accidental fires. Our study showed that numbers of warblers, at least of singing males, were lowest in the year of fire, but increased to higher levels in the year after burning and for several years after burning. We recommend that, in calcareous marshes which support up to 0.5% of the total population of this globally threatened species, intentional burning to control succession should be done before the arrival of warblers in spring in order to ensure burning is an effective management tool.