Tim Reed, from the Friends of Holt Island Nature Reserve, explains how nature never stands still.
The reedbeds have been a feature of Holt Island, St Ives, since the 1930s when reeds began to colonise an area of previously open water.
A century later, the beds can appear as dry land, but are actually floating over open water on a relatively thin (one metre) layer of vegetation.
Over time, the reedbeds are drying out and becoming less attractive to the summer breeding birds. They now mainly use the riverside margins of the bed for their nests. The question posed was, could we re-invigorate the bed and encourage more warblers back?
We clear-cut (right down to the ground) two trial areas in February 2023, and monitored their regrowth in several small 1 x 1m areas. We watched the birds’ response to them over two years, and we also looked at two nearby areas that were left uncut for comparisons.
In 2023 the clear-cut areas grew rapidly, overtaking in height the uncut areas by the end of the season. And by 2024, the previously clear-cut plots were generally higher than the uncut areas.
So, the good news is that we have a section of physically recovered reedbed, but what of the birds? In 2023, the regrowing bed was being used by the mid/end of the season, and the uncut area was only occasionally used.
In 2024, bird sightings in the regrown areas were up, matching the riverside edge, and more than in the uncut reedbed.
Birds were observed fighting in the regrowth areas, and carrying food items into it; suggesting that, from a bird’s point of view, the cutting and clearing had reinvigorated the reedbed.
What next? Two areas where the growth in the uncut reedbed seems thinner, and more overgrown with bindweed and hops, were cut in late February.
Bindweed and hops occurred in the regrown clear-cut areas. Neither did well, as the reinvigorated reed cover closed in and blocked out light in both years.
In addition to the birds competing for the improved areas of the reedbed, it looks like the plants are too. Clearly, everything wants a piece of the action as we actively manage the site for the better. Come and see for yourself. We hope to open again in early April, but do check the website and Facebook first!
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