Monday, 2 November 2015

Harvest Mouse Field Signs

Yesterday I went on a training day at Chimney Meadows, a BBOWT reserve a few miles south of Witney on the Thames.  The purpose was to look for signs of harvest mouse activity, one of the smallest mammals in Britain.  I have only ever seen one.  

Chimney Meadows
The training was led by Dr Amanda Lloyd who passionately works with BBOWT on dormice and other small mammals.  The idea of the training day was to look for harvest mouse nests.  I was a bit non-plussed by the idea of looking for nests in November - surely they nest in cereal crops, harvested months ago.  Every picture I have ever seen shows the mouse just below a wheat cob or similar.  Wrong.  They are just as happy, if not happier in tall scrubby field edges.

Harvest mice live for around 18 months; only a small proportion of the population overwinter.  There was no expectation of seeing animals, and indeed we saw none.

Last November, Dr Lloyd had found over 100 nests last year in a 30 x 200 metre field edge  that we were about to survey.    

This year with 15 surveyors we found only 13 nests, so quite a decline.   Such dramatic swings in numbers are not a cause for too much concern though.   They are regular but poorly understood.   

Nests are hard to find.   Mostly in amongst Tufted Hair grass (Deschampsia cespitosa) from a few centimetres up to 30 to 40 centimetres above ground, and amongst Phragmites and Himalayan balsam, the nests are up to 10 cm wide, made up of woven strands of grass leaves.   The star find was a nest in an almost impenetrable reed thicket.   I found none in three hours of searching.  Had this been a task on the Apprentice, I would have been fired.
Harvest Mouse Nest

Harvest Mouse Nest
Turning away from mice nests one of the party found owl pellets, which two of the party enthusiastically took for analysis.

Owl Pellets
My contributions were more prosaic, a few late flowering plants, hoverflies and other flies.  
Water Chickweed
Hoverfly (Syrphus vitripennis)

Scented Mayweed

Celery-leaved Buttercup

There were surprisingly few fungi; in amongst the grassland I did find a Common Fieldcap (Agrocybe pediades).
Common Fieldcap

Common Fieldcap Spores
It was a good day.   My challenge is now to find Harvest mice around Hooky where there seem to be no recent records.  

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