-------Received 14 January 2008; revised and accepted 21 May 2008------- Habitat requirements of Orthetrum coerulescens and management of a secondary habitat in a highly man-modified landscape (Odonata: Libellulidae) Hansruedi Wildermuth Haltbergstrasse 43, CH-8630 Ruti, Switzerland. <
[email protected]> Key words: Odonata, dragonfly, Orthetrum coerulescens, habitat use, habitat recognition, habitat management, conservation, Switzerland. ABSTRACT Due to the destruction of its primary habitats, the West Palaearctic libellulid Orthe trum coerulescens has suffered much decline in central Europe. However, at the re gional scale it has survived in a variety of secondary habitat, such as draining ditches. In order to find adequate measures for its conservation and promotion, habitat use and habitat recognition of 0. coerulescens were investigated by description and ex perimentation at fenland ditches in a small nature reserve in the Swiss Plateau. This breeding habitat, which harbours a viable population, had been restored and main tained for 25 years. The most densely populated sites comprised small ditches be tween 40-70 em wide, with rather sparse vegetation of narrow-leaved plants and that had parts of the water surface uncovered; the peaty, mud ground was partly overgrown with submerged pads of stonewort (Chara spp.). Water was mainly sup plied by seepage springs with a mixture of local slow flow that were hardly recog nizable and shallow sites, which were used for oviposition. In hot summer spells the water temperature could exceed 30°C. Some freezing occurred in winter, but the mud was permanently ice-free. The development of the breeding population, which comprised more than 200 individuals in 2006, was followed over two subsequent years.