The latest report from Michael Walter:

 

You know it’s spring when you can smell the bluebells, and I endeavour to make the most of that delight in Blean Woods because they aren’t very abundant. Intrigued by their patchy distribution, in 2016 and 2017 I plotted all the colonies I could find, large and small.  The resultant map is interesting as, with a few exceptions, all the bluebells occur near the woodland edge or along the main stream through the centre of the wood.  This suggests that two factors may be at work here - soil and light.  Over millennia the stream has carved a shallow valley through the upper layer of acidic, gravelly soil to reach down to a more clayey, less acid stratum which supports a number of species, such as hazel, that are uncommon in the rest of the wood.  So that could account for the presence of bluebells in an azure ribbon along the stream.  At the wood edge the plants may be benefiting from the extra light filtering through the trees, but soil may have an impact here, too.  The outlines of our woods are largely defined by how far our ancestors decided to push back the wildwood boundaries when creating new fields, preferring to restrict themselves to the more fertile soils.  It is therefore likely that woodland clearance around the edges of Blean Woods was halted well over a thousand years ago when farmers reached poorer, “hungry” soil.  The soil at the edge of the new fields may still have been an improvement on what was to be encountered a hundred or more metres into the wood, and that might just be enough to encourage colonisation by bluebells.

 

Willow warblers and chiffchaffs are closely related, and almost identical in appearance but, thankfully for birdwatchers, have radically different songs – the sweet, gentle melody of the willow warbler contrasting starkly with the two simple, staccato notes of the chiffchaff. Occasionally, though, complications can creep in.  This spring one particular bird has regularly started off with typical chiffchaff song, only to segue into the pretty descending scale of a willow warbler.  Which species is the mystery bird?  Are these intermediate individuals hybrids?  That is possible, although to my knowledge DNA testing has not been conducted to establish this.  An alternative explanation is that, having recently evolved from a common ancestor, the birds retain the potential to sing the song of either species, and my money is on the willow warbler being able to introduce the simple “chiff-chaff” metronome into its repertoire, rather than a chiffchaff managing to mimic the far more complex song of a willow warbler.  Genetic analysis has now advanced to the point where a species’ DNA can be decoded from a sample of its excreta, so you don’t even have to catch the bird, and it may soon be possible to determine if hybridisation is occurring.

 

New species of flowers still occasionally take me by surprise in the wood, the most recent being a single plant of greater celandine, which is actually a poppy, not a celandine! An ancient introduction to the UK as a garden plant, its position beside the reserve access track lends credence to the suggestion that it is not really growing wild at this site.

 

 

Michael Walter

michaelwalter434@gmail.com

01227 462491

 

Simplified map of bluebell distribution in Blean Woods 2016-17


 

Single greater celandine in Blean Woods – a probable garden escape


 

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