After our refresher day at Feckenham Wylde Moor on 30th September, I hope WMG members have been able to start searching for harvest mouse nests?  It is good to get out before the end of the year if you can, before wild wintry weather further flattens the vegetation!

A big part of the challenge of harvest mouse surveying, I have learnt, is identifying suitable blocks of habitat to concentrate upon: so many places are unsuitable because they are too mown, grazed or otherwise managed so that there is insufficient tall, grassy, sedgey or reedy vegetation in which harvest mice can weave their tiny, elevated nests.  I have been very fortunate recently in visiting two Worcestershire sites with abundant suitable habitat, and I found evidence of harvest mice at both of them!  Both are nature reserves, so not typical of most of our countryside, but I thought it was worth sharing my experiences in case it helps to guide you to your own successful search.

The first site was Avon Meadows Local Nature Reserve at Pershore, where WMG did some live trapping of small mammals in October.  On that visit we were struck by the abundance of tall, wetland vegetation at this lovely site (managed by Liz Etheridge of Wychavon District Council), so I looked forward to an opportunity for a nest hunt.  That soon arose in November when I chose Pershore as a place to meet up with an old friend for a walk and a chat, and I introduced him to the thrills of ‘swimming through long grass’, as harvest mouse surveying could be called.  There we found a harvest mouse nest in a tall stand of hairy willowherb with common reed; the delicate woven nest was just 7 cm across and suspended some 60 cm above the ground.  Although I knew what I was looking for, the discovery took my breath away and left me marveling at the aerial skills of our tiniest rodent that enable it to weave such a work of art two feet above the damp ground.

There is lots more suitable habitat to search at Avon Meadows, so we are planning another group event there on the morning of 15th December.

The second site I have been privileged to visit is the Worcestershire Wildlife Trust’s reserve at Hill Court Farm near Longdon.  With my colleague Charlie Long I searched just two fields in this huge site, where the main objective is to restore the wetland habitats that have been lost or damaged during decades of intensive farming.  Most of the vegetation suitable for harvest mice in these grassy fields is concentrated around the margins, where uncut headlands comprise tall, coarse grasses supported in places by blackthorn, wild rose and bramble spreading out from the gently-managed hedgerows.  The suitable vegetation here is mostly shorter than at Avon Meadows, so the bending over to search is more severe.  In a foolish and pointless effort to mask the growing pain in my back I imagine myself as an international rugby player competing for the ball at a ruck (picture the All Black flanker Richie McCaw 40 years on – grey-haired and wizened, but still determined to win the ball….); but it doesn’t work, so we had to take frequent breaks to stand up, stretch and enjoy the view of the Malvern Hills, marred only slightly by the sound of the M50 Motorway!

In all we found four perfect harvest mouse nests in just one of the fields at Hill Court Farm; all were tightly-woven near-spherical bundles of grass leaves 7-8 cm across and mostly 20 cm or less above ground level.  Some of the nests were still partly green thanks to the cunning harvest mouse habit of weaving in some grass leaves that remained attached to their stems so that they stay alive to help camouflage the nest (talking of ‘Staying Alive’, I find that frequent survey breaks to dance to the Bee Gees 1977 song of the same name are a good antidote to back pain).

Finding four nests was the result of about 6.5 person-hours of searching, so each nest took just over 1.5 person-hours to find; not a very impressive success rate, but we are relative beginners and doubtless there were some nests that we didn’t spot. It’s true that, depending upon the structure of the vegetation, the tiny nests can be very easy to miss if you are not right up close, so thorough searching is a slow process.  But each nest discovery is a delicious thrill, and we wouldn’t want it too easy, would we?!  Apart from a stiff back and a few scratches, the only downside to harvest mouse surveying is that one’s entire concentration is low down, so it’s easy to miss out on other wildlife sightings and the general countryside views; therefore, it is essential (and good for the back) to stand up every few minutes to take a look around and enjoy your surroundings!

Johnny Birks

3rd December 2018.