Cutting reed beds while protecting bird diversity

Posted on December 18, 2015

The common reed (Phragmites australis) occurs throughout the world and provides habitat for a wide range of animal species, including a number of reedbed specialists. Although reeds are commonly cut for commercial reasons and to prevent plant succession to wet woodland, it’s been shown that large-scale cutting can reduce the feeding and breeding success of resident birds. However, less is known about the effects of small-scale reedbed cutting. Researchers compared the densities of arthropod bird prey and the incidence of nest predation in (1) patches of cut reeds 0.5 – 2.5 ha in size, (2) similar-sized patches of uncut reeds located between the cut patches, and (3) an unmanaged (uncut) stand of reeds. Nest predation was assessed by placing artificial nests, each containing a quail egg and a plasticine “reed warbler” egg, among the reeds. Food densities were compared by sampling arthropods using pan traps containing a mixture of water and detergent. Nests and traps were retrieved after seven days. Based on marks on the real and artificial eggs, it was concluded that the main predators were large birds (probably marsh harriers), but attack rates didn’t vary significantly between cut, nearby uncut, and unmanaged areas. In contrast, densities of arthropods were significantly lower in the unmanaged plots than the other areas. Therefore, mosaic-patterned small-scale cutting may have a positive impact on prey numbers without increasing the risk of egg predation. The investigators inferred that the small cut patches were rapidly recolonised by insects from neighbouring uncut patches. More studies on the effects of reed cutting on insect dispersion and abundance are needed.

Reference: Trnka, A. et al. 2014. Management of reedbeds: mosaic reed cutting does not affect prey abundance and nest predation rate of reed passerine birds
Wetlands Ecology & Management 22, 227–234.