Individual study: Effect of winter cutting of reedbeds on the passerine breeding assemblage in the Camargue, southeast France
Poulin B. & Lefebvre G. (2002) Effect of winter cutting on the passerine breeding assemblage in French Mediterranean reedbeds. Biodiversity and Conservation, 11, 1567-1581
Common reed is increasingly harvested from the Mediterranean region to provide thatching material for north European countries. The aim of this study was to quantify the effect of reed cutting through a comparative analysis of water regime, vegetation structure, arthropod distribution and passerine assemblage at five commercial cut and eight uncut 'natural' reedbeds in southern France.
Study sites: The study sites located in the Camargue region of Mediterranean France (lat. range 42º51'– 43º38'N, long. range 2º8'– 4º52' E), were: five commercial reedbeds mechanically harvested between December and March every year (at two sites a few tiny patches of reed are left uncut); and eight natural reedbeds (two harvested until 1984 and 1990, others had never been harvested).
Cut reedbeds were characterised by a lower salinity, higher water level in spring, and higher reed biomass than uncut reedbeds.
Sampling: Each site had at least 10 ha of dense common reed Phragmites australis, in which two study plots 100 m+ apart, were sampled. In each plot, sampling was carried out along a transect 250 m long and 80 cm wide in May–June of 1998 or 1999. Data were collected on: abiotic factors (water level and conductivity), vegetation (reed structure and floristic composition on each transect), arthropods (sampled by sweeping the vegetation 500 times with a 30 cm diameter insect net along each transect), and birds (mist netting carried out between 19 May and 10 June in both years).
There was consistently more arthropod food available to passerines in the cut reedbeds. However, whilst the cut reedbeds had a similar bird species richness (main species were: moustached warbler Acrocephalus melanopogon, reed warbler Acrocephalus scirpaceus great reed warbler Acrocephalus arundinaceus, bearded tit Panurus biarmicus and reed bunting Emberiza schoeniclus) they had a lower overall bird abundance (33 vs. 44 captures) due to the significantly fewer moustached warblers and bearded tits at cut sites.
Conclusions and discussion: The mild Mediterranean winter favours early growth of reed in spring, making harvested reedbeds suitable for breeding of long-distance migrants such as the great reed and reed warblers. However, for the resident species (e.g. moustached warblers and bearded tits) that breed earlier in the season, cut reedbeds presumably lack sufficient cover to provide adequate nesting sites and insufficient feeding areas.
A biennial cut (double wale) is considered a good compromise between conservation and commercial interests in the UK. However, in the Camargue early reed growth in spring is favoured by the mild winter, and leaving dead stalks would only hinder new shoot growth; biennial cutting would result in a harvest comprising 50% waste matter without increasing the ‘good reed’ biomass. This management practice is therefore considered not economically viable by local reed harvesters. Thus a combination of annually cut and never cut reed patches appears the only sustainable alternative in this region. For conservation puposes, the authors suggest that a mosaic of cut/uncut reed patches could provide as high a conservation value as unmanaged reedbeds.
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