29 Aug 2012

Nature Notes – August 2012 by Pete Lambert

It rained and rained making water the constant theme of conversations and a daily test of clothing choices.  A long trek on a rare sunny day took me along the Monts canal as far as the Carreghofa locks, I had wanted to take a look at the unusual aquatic plants that I had heard were to be found in the water trough of the Vrynwy aqueduct. Canals when still in-water and before navigation erodes their wildlife interest are unique reservoirs of our rarest water plants. The action of motorised craft churn up the water, exclude sunlight, cause siltation and disturbance. It is very difficult to balance the needs of navigation with biodiversity, locally off-line nature reserves at Aston locks are part of this challenging struggle to match the pleasure of leisurely travel and conserving the unique niches offered by these man-made water courses.

 On arrival at the aqueduct I was to be disappointed, the ironwork must of  sprung a leak sometime since my last visit, plugs of clay had been placed at both ends and plant life was absent.  As some compensation Azure damselflies were out in great numbers, either as pairs caught in a mating loop or singletons confidently flying to and fro across the water. This section of the canal up to and just beyond Llanmynech is abundant in emergent vegetation, the aquatic damselfly larvae climbing these stems to fix themselves for their final transformation into the adult flying form. The Azure damselfly is a member of a family of red and blue damselflies all of which can be told apart by the variation of stripes of colour along the slim body and markings such as the ace-of-spades marking on the Common blue.

Parking awkwardly I leapt out to take a peek down onto the river Perry at Milford bridge near Baschurch. I had been here back in May to enjoy the rising mayflies and occasionally get a closer look as they rested  on the parapet. Today it was the fluttering and strikingly gorgeous Demoiselles. The Banded demoiselle has a very distinctive dark blue/black metallic stripe across its wings, the Beautiful demoiselle wings on the other hand are uniformly black with iridescent veins. Unlike the Dragonflies, the damselflies hold their wings folded upright above their narrow, slim bodies. The Banded demoiselle dominated the throng, its aquatic nymph preferring the gravels and weedy margins present along this stretch of the river. The Beautiful Demoiselle nymph seeks slower streams with muddy bottoms, which explains their greater abundance higher on the river where it flows slowly across Baggy Moor.

Along both canal and brook the Hemlock Water dropwort has been in flower. The umbels of tiny white flowers are held on numerous rays rather like an exploding snowball. Bright green ridged stems grow stoutly to form a large waterside plant. It is one of our most poisonous plant species, easily mistaken for wild celery and the cause of a number of tragic fatalities. It has a pleasant parsley aroma, but even this can cause light-headedness. Cattle have also succumbed when inadvertently brought down to graze on a waterside where the Hemlock Water dropwort can be found, this was certainly this case during a very dry spell during the 1990’s in the West Country. There are a number of other water dropworts in the UK all of which are poisonous. 

Considerably less menacing is the non-native Monkey flower. First discovered on islands just off the Alaskan coast in 1812, this yellow flowered plant easily naturalised here by the mid 1800’s and I found mine enjoying the very damp conditions within the disused lock at Carreghofa, the leaking lock gate creating a misty cascade and the ideal conditions for this unusual but colourful plant. 

As a final footnote to the wettest summer I can remember friends were surprised by the loud splash of a squirrel diving into the canal, swimming across to the far bank and then adeptly clambering out to loop into the woods beyond, the message, I think is, be adaptable!

Happy nature watching, Pete.