Projects
- Brown
Hairstreak survey & management
West Williamston Nature Reserve is
owned by the National Trust and managed by the Wildlife Trust of South
and West Wales. It is situated on the confluence of the Carew
and
Creswell rivers not far from Carew Castle. Deeply indented
with tidal
creeks, which were excavated over several hundred years as a result of
limestone quarrying, the narrow ridges and tidal islands left behind
now support a rich range of calcareous grassland and scrub woodland
communities. Scarce plants include the bee orchid
and marsh mallow.
The
foreshore, and to a lesser extent the tidal islands contain dense areas
of blackthorn which supports the largest known colony in Pembrokeshire
of the Brown Hairstreak butterfly.
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The
brown hairstreak is a
late flying, very elusive butterfly, spending much of their adult life
in the canopy of an ash or sycamore. Very few butterflies
hatch per
kilometre. To aid mating they use “master
trees”, particularly ash
trees growing near to the basin of the countryside that contains the
colony. Males perch on the master tree and as females emerge they fly
to the tree to mate. The females lay their eggs into
September and by
counting the eggs, white, bun shaped and about the size of a pinhead,
that we can assess the size of the population.
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Eagle eyed
volunteers have turned up to brave the elements for the annual winter
egg count since 1996. The numbers of eggs
found has fluctuated each
year between less than forty to several hundred. The most recent
survey, conducted in December 2004 revealed 125 eggs, which although a
steady increase overt the previous two years (double that of 2003)
falls short of the larger counts recorded in the past.
Management
is necessary to maintain the blackthorn in a condition where it
continues to provide suitable habitat for the butterfly to lay its
eggs. The Wildlife Trust organises a program of works
throughout the
year, which includes blackthorn management over the winter months at
West Williamston. An enthusiastic bunch of volunteers led by
the
Wildlife Trust have spent a number of days at West Williamston over
this past winter in a concerted effort to make the blackthorn more
attractive to female brown hairstreaks. We will have to wait
for the
result of the 2005 count to see if this has been successful.
Chris
Lawrence, Wildlife Trust Officer for Pembrokeshire
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