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Most reedbeds have to be cut if they are to remain as reedbed rather than succeed to scrub and wet woodland. But how often they have to be cut and the costs and benefits to wildlife of different cutting cycles have rarely been studied in detail. Work published by Jaap Graveland (J. Avian Biology 30: 469-482) on the density and nesting success of Reed Warblers Acrocephalus scirpaceus and Sedge Warblers A. schoenobaenus in reedbeds provides good evidence of the costs and benefits for these birds.
he study took place over three years at the De Weerribben National Park in the Netherlands, in areas of reed cut every year and every other year. Depending on the year, nesting densities of Reed Warbler were 1.2 to 2.5 times higher in uncut reed than in cut reed and Sedge Warbler nesting densities 6 to 50 times higher in uncut reed and other vegetation than in cut vegetation. Reed Warblers laid their first egg 6 to 12 days earlier in uncut reed than in cut reed. No significant effect on laying date could be found for Sedge Warbler. The predation rate for Reed Warbler nests in cut vegetation was 2.2 times higher and for Sedge Warbler nests 1.6 times higher than in uncut vegetation. For those nests which did survive and fledge chicks, there was no significant difference between cut and uncut vegetation in clutch size or number of chicks fledged for both Reed and Sedge Warblers.
It was concluded that uncut reed was more productive for nesting Reed Warblers, because it allowed them to nest earlier and thus to raise on average more clutches per season. It was also more productive for both Reed and Sedge Warblers, because their nests suffered much lower rates of predation. It was suggested that this was because of the greater visibility and accessibility of nests built in reed which had been cut the previous year. The study area did not include reedbeds which were cut on a longer rotation, and so the author was left asking the question of what was the effect of such rotations.
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