On the morning of Saturday 19 November, Ailsa Claybourn led a hunt for Harvest Mouse nests at BBOWT’s Moor Copse reserve near Tidmarsh. Also participating were members of the Berkshire Mammal Group, with the invaluable support of Dr Amanda Lloyd, an expert on small mammals. This nest hunt followed the discovery of the reserve’s first two Harvest Mouse nests in 2014, and a BBOWT hunt in 2015 which notched up eleven. The Harvest Mouse is Britain’s smallest rodent and our only mammal with a truly prehensile tail. They make nests in which to shelter, or raise a family, from spring to autumn, weaving them in situ. While Ailsa was explaining what the nests look like, Amanda spotted one in the brambly hedge next to where the group were gathered, and the hunt began. Ailsa had found the 2014 nests in Corner Field, but a determined sweep along the hedge line found only one more, so the group moved into Barton’s Field, where two nests had been found the day before. These were in tussocks of Cock’s-foot Dactylis glomerata and Tufted Hair-grass Deschampsia cespitosa; one had been appropriated by a vole overnight and incorporated into its nest! Nine more Harvest Mouse nests were found in Barton’s Field, predominantly near the boundary with Cottage Field. We crossed the boundary and Amanda was suddenly spotting nests like a greyhound on speed! The ground is soft and damp along the fence line, favouring the growth of Reed Canary-grass Phalaris arundinacea, which is clearly a very popular building material amongst Harvest Mice. The blades of grass are wider than Cock’s-foot, but still pliable and easily woven, giving a robust structural integrity. One of these nests was freshly made, reflecting the mildness of the autumn so far. As the winter progresses, the mice will move down to ground level, utilising other rodents’ burrows (and have been found in birds’ nests and haystacks). Eighteen searchers found a total of twenty four nests on the hunt, contributing valuable data to BBOWT’s reserves management team, and providing us all with a (mostly!) rewarding and interesting morning. The hunt was well-timed. Soon after, the weather changed, bringing heavy rain and wind, which quickly demolished many of the grasses, and their nests; the degradation of the Cottage Field site has been made complete by the hungry and inquisitive attentions of BBOWT’s Dexter cattle.

Report by Ailsa Claybourn