Chalkhill Blue explosion

[J.B.Murray]

I stopped off on the way to work this morning to walk a short transect I
have set up but not had time to do very often at Hexton Chalk Pit, an
HMWT Nature Reserve measuring about 200 x 100 metres.  The weather was
poor - about two-thirds cloud and a blustery wind, but in the 16 minutes
it took me to walk the transect I counted:

Large White:  1
Green-veined White: 3
Gatekeeper: 10
Meadow Brown: 27
Chalkhill Blue: 513

Yes, five hundred and thirteen Chalkhill Blues (Lysandra coridon)
counted in sixteen minutes in poor weather!  The numbers were difficult
to count, as there were between 5 and 20 males visible all the time as I
walked the route; except during the sunny periods, none were seen apart
from those that I had disturbed.  Male:female ratio was about 20:1 and
several mating pairs were seen.  Clearly the claims of Brian Sawford in
the 1997 butterfly report are not exaggerated; this tiny fragment of
habitat has seen a veritable explosion of Chalkhill Blue since the site
was first recolonised in about 1990.  The turf most favoured had been
fairly closely cropped, I think by rabbits, as there were plenty of
scrapes and much bare chalk on the sides of the pits themselves.  I
wonder what the count would have been in good weather?  

Clearly someone is doing something right in the way of management here.
The potential for Chalkhill Blue expansion also seems infinite at the
moment - a good time to set up Horseshoe Vetch plantations nearby, or to
introduce appropriate management on existing sites.  

John Murray
Marshalls Heath,      Email: j.b.murray at open.ac.uk
Wheathampstead,      Home 'phone:  01582 833544
Herts. U.K                 Work 'phone:  01908 652118