Reed cutting affects arthropod communities, potentially reducing food for passerine birds Martin H. Schmidt a, * , Ga€ etan Lefebvre b , Brigitte Poulin b , Teja Tscharntke a a Fachgebiet Agrar€ okologie, Universit€ atG€ ottingen, Waldweg 26, 37073 G€ ottingen, Germany b Station Biologique de la Tour du Valat, Le Sambuc, 13200 Arles, France Received 16 July 2003; received in revised form 12 December 2003; accepted 25 March 2004 Abstract Winter cutting of Common Reed Phragmites australis (Poaceae) is increasing in Camargue, southern France, potentially affecting wetlands of high conservation value. We studied its impact on arthropods by comparing four cut and uncut sites with special respect to avian prey availability in the breeding season. The two most important prey groups for breeding passerines, spiders (Araneida) and beetles (Coleoptera), were identified to species in trap catches and diet samples. The arthropod assemblages differed significantly between cut and uncut sites. Phytophagous and saprophagous species showed contrasting responses. Numbers of homopterans increased in cut reed beds, where green Phragmites stem density was higher. Saprophagous woodlice decreased, presumably due to the reduced amount of litter. Densities of some vegetation-dwelling spider and beetle species were lower at cut sites, including two of the most preferred prey species for passerine birds. Consequently, large-scale mechanically harvested reed beds host altered ar- thropod communities, missing major food components used by vulnerable passerines. However, reed cutting on a small scale may increase habitat heterogeneity and species richness on a landscape level. To contribute to reed bed conservation, EU schemes should reward management that leaves uncut reed patches in the proximity of cut areas to permit their recolonization by arthropods. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Araneae; Coleoptera; Phragmites australis; Disturbance; Biodiversity; Conservation; Habitat management 1. Introduction Monospecific stands of Common Reed Phragmites australis are widely distributed in European wetlands. They host a particular fauna with an outstanding pro- portion of habitat specialists, including insects, spiders and birds (Flade, 1994; Ostendorp, 1999; Tscharntke, 1999). Several of the bird species are considered vul- nerable in Europe (e.g., Great Bittern, Purple Heron, Moustached Warbler), and many reed beds are part of nature reserves. They are often cut in winter either for commercial or conservation purposes. Cut reed provides thatching and other building material, and harvesting is considered to counteract the silting up of reed beds and to enhance plant species diversity in the undergrowth (Cowie et al., 1992; Decleer, 1990; Hawke and Jos e, 1996). Cut reed beds are drained in winter to facilitate mechanical harvest, and irrigated in spring to enhance growth (Hawke and Jos e, 1996; Poulin and Lefebvre, 2002). In natural reed beds, green shoots emerge from a perennial rhizome in spring, grow over the summer, and die in autumn to persist as standing dry matter for several years. In harvested reed beds, the dry stems are cut about 20–30 cm above the ground in winter. With the removal of dry reed, nest building of early breeding passerines is prevented (Baldi and Moskat, 1995; Poulin and Lefebvre, 2002), overwintering stages of arthropods are removed or destroyed (Ditlhogo et al., 1992; P€ uhringer, 1975), litter input is reduced (Cowie et al., 1992; Hawke and Jos e, 1996), and temperature fluctu- ations and radiation at the ground level increase (Cowie et al., 1992; Decleer, 1990). The reed grows thinner, shorter and more densely, resulting in an increased primary production (Cowie et al., 1992; Ostendorp, 1999). * Corresponding author. Tel.: +49-551-392358; fax: +49-551-398806. E-mail address: m.schmidt@uaoe.gwdg.de (M.H. Schmidt). 0006-3207/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.biocon.2004.03.032 Biological Conservation 121 (2005) 157–166 www.elsevier.com/locate/biocon BIOLOGICAL CONSERVATION