To set the ball rolling, here's an article I penned for the Murray Downland Trust Seventeenth Annual Report (2011). It perhaps gives us hope that by working together and sharing ideas through a forum such as this, we can preserve this beautiful and charismatic butterfly for the enjoyment of future generations.
The
Dukes of Heyshott
The
Duke of Burgundy is one of the two most rapidly declining and threatened
species of butterfly in the UK, which together with the High Brown Fritillary
now faces potential extinction unless conservation measures are successful in
halting and reversing the current trend of population losses. Fewer than 100
colonies remain, with West Sussex being at the retreating eastern front of the
species’ geographical distribution, leaving just isolated outliers in Kent. The
vast majority of remaining colonies are very small, comprising no more than a
handful of adult insects on the wing at any time during its late April to early
June flight season. Populations where maximum daily counts exceed 30 butterflies
are now very rare and in 2003 the total number of Duke of Burgundy adults seen
in the county was 8. I remember Colin Pratt F.R.E.S., the county recorder,
showing me a histogram depicting the number of 2 Km squares occupied by ‘the
Duke’ since the 19th Century; extrapolation of the ever-downwards
trend clearly suggesting that the species was unlikely to outlive the second
decade of the 21st Century in Sussex. This is a butterfly in dire
straits.
The
Duke of Burgundy is the flyweight champion of the butterfly world, being so
pugnacious that all other species are attacked should they stray across the
male’s fiercely guarded territory, irrespective of their size. He is only as
large as one of the blue family. The males will often congregate in small
‘leks’ where in-fighting is almost constant between the hours of 11am and 3pm.
Although he can occasionally be seen outside these hours ‘the Duke’ is very
lazy, rising late and retiring early. Combatants typically spiral upwards in
vertical climbs of up to 50 metres before dropping back to their eagerly
contested perches on low scrub. The females are better behaved and go about
their business of laying eggs as discreetly as possible. These are deposited
singly, or sometimes in twos and threes, on the underside of cowslip leaves, or
on primrose in more wooded habitats. She is notoriously fussy about her selection
of egg-laying sites, this being a critical issue to which I will return. The
sexes are broadly similar in appearance, with a network of dark bars and
stripes over a ginger-brown base colour, giving the general appearance of a
fritillary; indeed this was once called the Duke of Burgundy Fritillary.
However, the taxonomists now place this butterfly in a family of its own, at
least in the UK, although there are relatives living abroad. At home ‘the Duke’
is unique in that the male has vastly reduced front legs and uses only the rear
two pairs for walking, whereas the female has all six legs fully developed.
In
West Sussex there are now less than a dozen sites supporting the Duke of
Burgundy and many of these could be lumped together, leaving just 5 population
centres. I personally began to work in earnest on ‘the Duke problem’ in 2005,
but it was April 2007 before I met up with Bruce Middleton and Butterfly Conservation’s
SE Regional Officer Dr Dan Hoare on the slopes of Heyshott Escarpment. At the
time the population here had hung on by its fingernails for many years, with
maximum daily counts of just 2 or 3 insects at the small ‘lek’ within
Compartment 10. Although the management of the reserve at that time suited most
of the flora and fauna, it was not quite right for ‘the Duke’. Since then the
Murray Downland Trust and Butterfly Conservation Sussex Branch have worked very
closely together in improving things for this species. Sometimes conservation
necessitates that we rob Peter to pay Paul and it is difficult to please all of
the plants, invertebrates and those further up the food-chain all of the time.
However, the MDT project team led by Mike Edwards has done a fantastic job in
doing just this, although it is of course vital that ongoing monitoring gives
early warning of any disadvantageous changes in the other valuable inhabitants
of this wonderfully diverse site.
At
the moment everything seems happy, while the results achieved so far for the
Duke of Burgundy have been nothing short of remarkable. As changes in the
habitat management took effect maximum daily counts began to rise; 7 and 8 in
2008 and 2009, then leaping up to 51 in 2010 and a mighty 115 this spring (2011).
It is rare for the term ‘population explosion’ to be applied to this butterfly
and these figures buck the national trend, proving that the decline can be reversed where focused efforts
are made to satisfy its highly fussy needs. Similar results have been achieved
on another Sussex site over the same time period. There are other winged
beneficiaries too, as nationally declining species such as the Dingy Skipper
are doing exceptionally well here. This butterfly also prefers that seemingly awkward
ground between early and mid succession habitats. And there’s the rub. It is
only by targeted management that some species with very particular requirements
will thrive. It is these species which unfortunately often suffer (and
sometimes go extinct) at the hands of a one-size-fits-all philosophy for
managing ‘whole habitats’ such as calcicolous grassland. It is due to the care
and attention to detail given to the MDT management plan that these tricky
species are doing so well, alongside thriving populations of their less
demanding neighbours.
So
what is it that makes life so difficult for the Duke of Burgundy, whose
food-plants are so widespread across superficially suitable tracts of our
landscape? As always with these species the devil is in the detail. The
cowslips must be in the correct growth form and in a precisely suitable
position for the fussy ‘Duchess’ to consider leaving one or two of her pearly,
pale green eggs behind. Leaves that are medium or large sized, fleshy and
semi-erect are strongly preferred and these are often found where slightly
longer swards are developed, often in the shade of taller scrub or trees, or
where ‘soft’, advancing, low scrub edges are to be found. Turf which is
over-grazed by the more familiar breeds of sheep soon becomes unsuitably short
and tight, hosting only small cowslips with tiny leaves pressed close to the
ground in fear. The situation only becomes worse when the rabbit follows with
enthusiasm. Scrub cutting must be truly rotational, as continually cutting to
the same template soon creates ‘hard’, unsuitable edges. Nearly right is not
good enough for this butterfly.
Of
course Heyshott Escarpment is not just about the Duke of Burgundy. It’s a
fabulous place to visit at any time of the year, with views from the upper
levels which are hard to beat anywhere within our National Park. But springtime
is the time to be here, when the
early orchids are in flower and ‘the Duke’ is on the wing. The supporting cast
is strong, including Dingy and Grizzled Skippers, Brown Argus, Common Blue and
the Green Hairstreak, a butterfly so exotically green that it would not look
out of place in a South American rainforest.
As
winter approaches I look forward to joining MDT and BC Sussex volunteers on the
reserve, where there will be much to do if the exciting plans for this coming
work party season are to be completed. This will make even more room for,
amongst other things, this charismatic little butterfly. Heyshott Escarpment
has already achieved a position amongst the very best Duke of Burgundy sites in
the UK. Only time will tell just how good it can get.
FOOTNOTE: Duke of
Burgundy numbers fell back significantly during the spring of 2012, as they did
on the majority of sites. This was undoubtedly due to the exceptionally adverse
weather suffered during the period before and throughout most of the flight
season. However, larval survival is likely to be high due to the good condition
of the food plant and we will hopefully see a recovery in numbers over the next
year or two.
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