Saturday, 27 April 2013

Bath City Farm

Spring Natural History Day at Bath City Farm. 27th April 2013.

Sixteen members and guests attended this event on a cool but mostly dry and at times quite sunny day that looked and felt more like March than late April. We gathered at first for an introductory talk by Alan Rayner in the newly built training room, where our display stand used at the recent Lakeside Optics Bird Fair was also set up. Then we set out for a walk around the Farm, to get an overall feeling for the diverse grassland, woodland, scrub, hedgerow, wet ground and pond habitats it contains. We noticed some considerable differences in plant species diversity between grasslands on the upper and lower slopes and spent some while examining woodland flora and fungi on decaying wood. A majestic hollow beech tree within which tiers of fruit bodies of Coriolus versicolor and rarer Coriolus zonatus were growing attracted our attention. This provided Paul Wilkins with a chance to explain what he called ‘angel wings’, forming where adjacent trunks fused, and why the tubular structure of the hollow trunk was mechanically strong enough to support a large, high canopy.  A variety of birds were seen and heard, including lesser whitethroat amongst the latter. We returned to the training room for lunch and conversation, then set out again, as a smaller party, for a more detailed examination of grassland biodiversity, led by Alan Feest, who showed us how to conduct a structured survey using no more than three bamboo canes and a 4 m dog lead. We found this very enjoyable and instructive, demonstrating both how quantitative data  can be gathered in a scientifically useful way, enabling changes in species composition to be detected, and how much more can be found when our attention is carefully focused – as when Andrew Daw picked up a tiny grass snail. Just seven plant species were recorded within a 50 m 2 circle in the upper grassland, whilst nineteen were found in the lower grassland. We hope to do more of this on future Nats field excursions. 

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