Over the weekend we found numerous little platforms of reed and sedge, the leaves and stems cut into short sections and left with ragged edges. In some respects these platforms looked like the beginnings of those used by moorhen and coot for nesting but the presence of small, blunt-ended droppings revealed that they were, instead, evidence of feeding water voles. In one particular corner of our study site the density of these platforms within the fringing reedbeds implied the presence of a healthy population of water voles, which is wonderful news given the decline in fortunes of this fantastic riparian mammal more widely.
As if to reinforce just how well the water vole might be doing on this series of old gravel pits, later that morning we chanced across an unexpected interaction between a water vole and a pair of the reed warblers that we are monitoring for a project on the species. This particular pair had built their nest in a reedbed located within one of the shallow pools at the south end of the site; this being the area where the water vole activity appeared to be most marked. As we approached the pool we could hear alarm calls and it was apparent that the reed warblers were very agitated about something in the water below the nest. The birds flicked about between the reeds, diving down at some intruder hidden from our line of sight. The intruder was not enjoying this unwelcome attention and the reed stems twitched violently as whatever it was attempted to dodge the blows that the warblers were directing towards it.
Dave was able to edge closer to the bed, seeking to get a better view, because the warblers and whatever else was in the reeds with them were so focussed on each other. It was not until Dave was within a few metres of the nest that he was spotted, a loud ‘plop’ revealing a water vole that disappeared into the water and away. Closer inspection suggested that the water vole had been busy feeding near the base of the nest. Had the vole decided to feed on the stems supporting the nest cup itself, the nest would have been lost. It was no wonder that the reed warblers were concerned for their clutch of eggs.