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Habitats in Britain
& Europe
1 - Forests and woodlands
2 - Grasslands and scrub
3 - Heathlands and moors
4 - Coastal habitats
Grasslands
Uncultivated
grasslands are amongst the most important habitats for butterflies.
If suitably managed they become carpeted in wild flowers such as
birds foot trefoil, hairy violet, cowslip, horseshoe vetch, kidney
vetch, common rockrose, devil's bit scabious, sheep's sorrel and
creeping cinquefoil. Each of these plants serves as the larval
foodplant of a particular species of butterfly.
These and
many other wild flowers such as marjoram, thyme, knapweeds, self
heal, germander speedwell, buttercup, dandelions and daisies are
also extremely important as nectar sources for the adults.
Finally of
course are the grasses - fescues, bents, couch, timothy, Yorkshire
fog, wood false brome etc; which are the larval foodplants of
various Skippers and Browns.
Chalk grassland at Cerne Abbas,
Dorset, England
Extensive
areas of calcareous ( chalk or limestone ) grassland such as the
South Downs, North Downs, Chilterns, Malvern Hills, Purbeck Hills
and Cotswolds can support enormous butterfly populations, but even
small areas of grassland, in woodland clearings, along railway
cuttings, in meadows and in abandoned chalk quarries are of immense
value if suitably grazed and managed.
Disused railway
line running through chalk grassland and woodland, Powerstock,
Dorset
Grazing and scrub
control
To ensure the continuing survival of a wide diversity of butterfly
species, it is essential to manage grasslands so that they support a
variety of different vegetation types.
Management has
to be tailored according to the situation - some sites, because of
their situation, can only be
managed by mowing or flail cutting, but cattle or sheep grazing
generally creates much better conditions for butterflies.
Sheep graze in
a manner which produces a uniformly fine sward, with a profusion of
vetches and trefoils, and creates a habitat particularly suitable
for certain blues and skippers.
Cattle grazing,
in conjunction with scrub control measures, has been shown to be the
best overall management technique however, as the grazing pattern
tends to create a mosaic of different sward heights, with a more
diverse flora that accommodates a wider range of butterfly species.
The timing
of grazing is extremely important - summer grazing can for example
have a detrimental effect on species which spend summer in the
larval stage, feeding on grasses or herbaceous plants.
Wild
rabbits are of immense value as natural grazers, particularly as
their excavations expose patches of bare soil where butterfly
foodplants can germinate. Periodic surges in rabbit populations
however can result in severe over-grazing that can easily wipe out
certain butterfly species. Stock densities of cattle and sheep
therefore need to be carefully tailored to take account of the
effects of rabbit grazing in any particular year.
Another
consideration is that each species of butterfly has different
requirements - some need the grasses to be lush and tall,
while others need it to be very short. The
Adonis Blue and Silver-spotted Skipper for example will only breed
at warm sites, favouring south facing slopes where the grass is
short and sparse.
Chalkhill Blues, Small Coppers and most other grassland butterflies
need a slightly taller sward of about 10cms, where the habitat is
moister and rich in wild flowers. Most of the Satyrinae and
Hesperiinae on the other hand require a sward of between 15 - 30cms.
Getting the balance
right, to create a habitat that will support viable populations of a
wide variety of species, can be very difficult particularly if the
site is small. Unfortunately it is sometimes necessary to prioritise
and cater for one particularly scarce species at the expense of
another. On larger sites this is less of a problem because different
parts of the site can be grazed at different times of year or at
different livestock densities, to cater for a multitude of butterfly
and moth species, while at the same time providing habitat for other
forms of wildlife.
Ramsdean Down,
Hampshire
It is not only the
grasses and wild flowers that need to be managed - a site left
unmanaged would within a few years become overgrown with bramble,
privet, dogwood, buckthorn, gorse, hawthorn and blackthorn bushes
which would shade out the herbaceous plants and grasses. Eventually
the site would revert to woodland, and all the wild flowers and
grassland butterflies would disappear.
Bushes therefore need to be
periodically cut back - a process known colloquially as
"scrub-bashing". It's very important however to get the balance
right, because a certain amount of bushy vegetation is beneficial to
butterflies, providing much needed shelter from wind and blazing
sunlight. Bushes also provide perching places which males use as
lookout posts from which to survey and intercept potential mates.
Excessive scrub removal can cause
major problems for butterflies, because many species lay their eggs
on herbaceous plants that grow around the base of bushes. If they
laid their eggs on plants in open areas away from bushes, the
resulting caterpillars would perish - either through desiccation in
bright sunlight, or because rabbits would eat the plants on which
they depended ( plants growing close to bushes are normally ignored
by rabbits ).
Grassland butterflies thrive best,
both in diversity and abundance, at sites where a well considered
grazing and scrub control regime produces a mosaic habitat in which
bare ground, short turf, lush vegetation and bushes are all
essential elements.
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