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A quick spot check

Have a look at these general management guidelines to help maintain valuable grassland for butterflies:

• Ideally, survey a site (plants and invertebrates) before changing management. Take advice for managing specialist habitats or where rare species are known to
occur on the site or nearby.

• Aim to create a varied grassland sward with scrub, long grass and short turf that suits a variety of species – consider all management options in the context of
the site’s traditional management.

• Avoid fertilisers and herbicides on all grassland – this can destroy larval food plants.

• Retain ditches and damp areas as these provide suitable conditions for wetland plants such as ladies smock and tufted hair grass which are host plants for the orange tip and ringlet butterflies.

• Avoid tidying all rough grass areas such as verges against hedges – to avoid scrub encroachment cut one third of verges each year in spring or autumn, rotating on a two to three year cycle.
 

Butterfly rarities, priority species or rare habitats


Contact Suffolk Wildlife Trust for further advice and specialist grassland advice if:

• You have semi-natural specialist habitats – or your neighbours do - such as chalk grassland, chalk pits, Breck grassland, heathland

• You know of records of any of the following rare butterflies or moths with specialist grassland habitat requirements on your land or close nearby including
the following: Dingy skipper, silver-studded blue, brown argus, wall, grayling, and small heath.

Invertebrate species associated with these habitats have very precise microhabitat requirements. Orientation of slope, connectivity, degree of shading of food plants and shelter are all critical – so manage these special habitats very carefully.

Call 01473 890089 or email info@suffolkwildlifetrust.org

Grassland management for butterflies

Meadow brown by Amy Lewis Meadow brown by Amy Lewis

More than 20 butterfly species regularly breed in Suffolk on suitable grassland and field edge habitat including species-rich pasture, rough grass margins and nettle patches on field edges and awkward corners, scrub, woodland and hedges.

Species-rich grassland provides food for developing larvae on grasses and flowering
plants, while nectar-filled flowers feed adult butterflies, moths and other insects. But with careful management and by ensuring there are good nectar sources within reach, even fairly species-poor grassland can be invaluable to certain butterflies whose larvae feed on grasses.

Greyling by Bill StevensonA grassland 'mosaic'

As with managing grassland for other invertebrates butterflies require a varied topography and a habitat that can sustain them throughout the year. A grassland mosaic should include:

• Patches of bare ground – some butterflies require sunbaked bare ground for basking in

• Short open turf – essential for non-competitive host plants such as birds’ foot trefoil

• Tall grass – small and large skippers will lay eggs on grass such as cocksfoot and many species over-winter in grass sheaths

• Tussocks – Yorkshire fog and cocksfoot are eaten by caterpillars of speckled wood and wall brown butterflies(and many others) and tussocks provide essential over-wintering cover

• Plants in all stages of development ie flowering for nectaring and with dead seed heads and stems for some species to over-winter in

• Ideally, nearby scrub or hedges – on which the adults feed, rest, sunbathe and use as a corridor, linking different areas of suitable habitat.

• A nectar-rich food source over a long season, provided by varied trees, shrubs and flowering plants in a range of nearby habitats

• Good, undisturbed egg-laying habitat – tips of grasses, flowering plants and shrubs that won’t get cut or browsed before eggs have hatched and developed successfully

• Plant diversity and structure is important – many species will only lay their eggs on a particular food plant. The larvae of the whites feed on a range of cruciferous plants, whilst the blues and copper require more specific, and often rarer, larval food plants. The larvae of the various browns and skippers feed on relatively common grasses in hedge bottoms, and then depend on flower and shrub nectar as adults. Nettle
feeders often hibernate as adults in hollow trees and wood piles along hedgerows

• A varied topography is beneficial such as provided by ant-hills and old earthworks, providing warm southfacing slopes and sheltered areas.

Continuity of management

Avoid sudden management changes. Crucially, deciding how to manage an area of grassland should take account of the site’s management history. Grazing or cutting favours different plants and therefore associated butterflies and moths. Over time with the same annual management, a community of plants and insects will have adapted to suit this regime.

Suddenly changing this regime, even for just a year, may irreversibly harm a butterfly or moth species – and still not actually encourage a greater diversity in its place. If conditions become unsuitable for a species, even for only a few months, then that species can become extinct on that site, especially if there is no suitable corridor along which to re-colonise from elsewhere.

Hay meadows and mowing

Hay meadow management is excellent for flowering plants, but for butterflies the hay cut can be catastrophic. The cut removes both nectar-rich adult food plants and plants on which eggs may have been laid and larvae are feeding. The small copper survives hay meadow management by having several broods a year. The first brood is laid on large tender sorrel leaves growing in long grass but subsequent broods are laid on small sorrel plants in the aftermath of a hay crop.

• Where mowing is the only option, cuttings should always be removed (to avoid a mulching, enriching and smothering effect), ideally as a late hay crop (mid- July).

• Some areas (up to one third) should always be left uncut each year to continue to provide some nectar, to allow a proportion of butterflies to complete their life cycle and to provide over-wintering areas. To prevent scrub encroachment from hedges this uncut area can be rotated around or alternated each year.

• If possible find out the traditional date for cutting your site before changing it, as doing so may completely change the plant community and thus the associated invertebrates. A late hay cut in mid-July is probably the least damaging for butterflies. But it may be better to cut part of the meadow earlier in June and cut the second part later in July to ensure some continuity of flowering plants (essential nectar) and some standing seed heads and stems over winter.

Meadow brown by Bill StevensonGrazing management

Choosing the appropriate grazing animal, stocking level and timing of grazing is dependent on many site factors. Be cautious – it is better to trial-graze small areas or under-graze a whole site, assess the impact and then adjust management, than to ‘blitz’ a site and possibly cause local extinctions. Ideally, aim to create a varied sward where a proportion of the tussocks, standing dead seed heads and some plant litter should still remain at the end of the grazing period.

Grazing at a low stocking density (less than one cow per hectare or between one and three sheep per hectare ha) is a gradual process that avoids sudden, drastic changes to a site and can produce a patchwork grassland required by different butterflies ensuring a longer season of larval food plants and adult nectaring plants. See the table below for grazing management options on different sites.

Cattle grazing is usually preferable to sheep grazing as cattle’s selective browsing produces a better patchwork of varied sward height. Rotational grazing with tethered sheep or goats can produce the same effect within small areas but untethered tend to produce a more uniform and less beneficial sward.

Horses produce enriched latrine areas and hard-graze elsewhere and are thus more suited to grazing large complex areas at a relatively low stocking density.

Grazing management to benefit butterflies on different grassland sites

Management option

Suitable site

Grazing
objective

Benefits to butterflies

Winter grazing
(October to March)
Infertile, dry sites
prone to drought
Sites grazed by
rabbits in summer
months
At the end of the
grazing period a
proportion of the
tussocks, standing
dead seed heads
and some plant litter
should still remain.
They may appear
‘under-grazed’ to
farmers
Keeps down coarse grasses, benefits
uncompetitive plants. Least damage done
to larval and pupal stages as they are
dormant and tucked well down into cover
Early summer grazing Wetter, more fertile
soils which need
rapid plant growth to
be kept down
Keeps down coarse grasses, benefits
uncompetitive plants which subsequently
flower in late summer, providing good
egg-laying sites and larval food plants
Light summer grazing Only suitable if very
light grazing only – on
more fertile non-droughty
site
Create diversity in
sward height with
plenty of flowering
plants and tussocks.
Fine tune grazing in
periods of drought
Few benefits – heavy summer grazing can be very damaging to butterflies.
Rotational grazing (around
compartments or tethered
animals) – several times a
year on fertile sites, less
on infertile
Where site is divided
into compartments
but only suitable
where larval and
nectaring plants are
evenly distributed.
Create diversity in
sward height with
plenty of flowering
plants and tussocks
in each
compartment.
Allows mobile butterfly species to move
to most suitable habitat and it can be finetuned
to ensure there are always some
flowering plants.
Light continuous grazing Only suitable with
light grazing on site
with a diverse
topography and
habitat.
Create diversity in
sward height, light
enough grazing to
allow plenty of
flowering plants and
tussocks in summer.
Fine-tune during
drought.
Keeps down coarse grasses but on a flat
fertile site a uniform sward will probably
result. Can produce a varied sward.
Opportunistic grazing to
‘blitz’ a rank site
Only suitable as part
of a careful
management plan.
Botanical objectives
may outweigh
invertebrate
priorities.
May benefit flora but may eliminate
insects. With good habitat links,
butterflies may re-colonise.