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NETTLE
LAKE BUTTERFLY RESTORATION/CONSERVATION PLAN
Because the majority of butterflies are
generalists with respect to their nectar plant needs,
restoration should primarily consist of supplementing their
diet with both native and cultivated plants known to be used
by several species. This is called a coarse-filter approach
- in most cases, successful butterfly habitat enhancement
won’t require a species-specific approach, unless there is
a glaring gap in a life cycle requirement, or for an
especially desired species. Britain has a long history in
butterfly monitoring and conservation, yet even their
success in managing reserves for rare species has been poor.
This is yet another reason for managing
common species before they become rare. Also,’ most
butterflies have relatively small home ranges and/or
territories, in contrast with many other wildlife species,
thus some species potentially “fall through the gaps;”
established reserves likely will not be successful in
preserving all species. This is an area where actions by the
knowledgeable private landowner can have a measurable effect
on the success of conserving species.
Causes of declines of butterflies in Ohio
are likely to be losses of areas with suitable food plants,
due to agriculture, or changes in the character of usable
sites, such as draining or degradation of wetlands. Many
aspects of modern farming decrease the probability of
survival of all but the most mobile and least demanding
species. Raising crop plants removes large blocks of habitat
for most butterflies, and any remnants such as field margins
are often further degraded by specific land-use practices.
Potentially, restored, high-quality field margins could
serve as corridors of movement or dispersal for some
species, although there is no direct evidence for this yet
in butterflies. Here are some possible suggestions to
ameliorate the negative effects of agriculture, based on
an intensive series of large-scale experiments conducted on
the management of field margins at Wytham, by the University
of Oxford’s Wildlife Conservation Research Unit.
Mowing: Well-timed mowing, both in
spring and autumn, may result in significant increases in
numbers of butterflies observed, versus summer mowing. (This
effect was observed for all three years surveyed
post-treatment in the British study). Summer mowing was
detrimental to butterfly abundance primarily because of
removal of nectar sources. No significant differences in
abundance or species richness of butterflies was observed
between field margins that were never cut and those cut in
spring and autumn.
Sowing: Sowing field margins with a
mixture of wild grasses and forbs, including several
important nectar sources, may result in increased abundances
of butterflies, over margins allowed to regenerate
naturally.
Spraying: Glyphosphate herbicide
spraying is clearly a devastating management practice on
butterflies, by significantly lowering numbers of
perennials, resulting in a decrease in nectar supply and
larval food-plant availability. Likewise insecticide
spraying is equally harmful.
Monitoring butterfly response would clearly be
valuable if such practices were employed at Nettle Lake; I
know of no such large-scale experimentation in this country.
Wetland loss and degradation undoubtedly have
negatively affected some butterfly species in Ohio. Of the
species occurring or potentially occurring at Nettle Lake, a significant number (31% of the skipper and 24%
of the true butterfly species) have wetland habitat
associations. These wetland habitats include wet meadows,
sedge meadows, fens, seeps, streams, and ponds. Of the four
species designated threatened or endangered, three have
definite wetland ties. In Ohio, the Two-spotted Skipper
is restricted to sedge meadows and fens, the
Puplish Copper inhabits disturbed moist
areas, such as wet ditches and damp areas of cultivated
fields, and the Regal Fritillary occurs
in mesic prairies grading into wetlands. The Silver-bordered
Fritillary is the only threatened or
endangered species not specifically requiring wetland
habitat, but it does tend to occur in damp areas such as
sedge meadows and moist old fields.
Ohio has already lost 90% of its wetlands, and many of the
remaining ones are degraded, or under pressure to be filled
or drained. To conserve butterfly diversity and rarity at
this site, preserving wetland habitat is imperative.
On the landscape level, adjacent CRP
(Conservation Reserve Program) land may serve as a source of
species and/or individuals to Nettle Lake. Established by
the Food Security Act in 1985, this program has positively
affected many vertebrate species by removing highly erodible
land from production, and planting vegetation especially
suited for wildlife food and cover. It highly likely that the CRP has been beneficial for
butterflies as well.
Backyard gardening is the primary means by
which plants can be introduced to enhance butterfly habitat,
and the Nettle Lake property owners can contribute towards
this restoration plan, with the designed to provide
resulting whole perhaps being greater than the sum of its
parts. Gardens can be habitat for a wide variety of
butterflies. Plantings of local native food species for
butterflies may aid in reducing the isolation of native
plants in reserves and parks, and provide essential
stepping-stones between remnant habitat patches. Contiguous
or proximate habitat patches may be important in the
metapopulation dynamics of some species - species that are
characterized by shifting mosaics of temporary populations
linked by some degree of migration.
An idealist might recommend using native plants
only, but realistically, butterfly gardening represents a
compromise between butterfly needs and the aesthetic
preferences of landowners for their own gardens, thus most
gardeners will probably want to use cultivated plants as
well as native plants. However, some plant varieties have
been bred for color, showiness, or other characteristics at
the expense of nectar production, so simple varieties are
generally better choices. Conversely, some cultivated
varieties of wildflowers, such as purple coneflower bloom
longer than their native cousins.
Some general principles in butterfly garden
design are: those most successful at attracting butterflies
are located on south-facing slopes, with species planted in
clusters rather than as individual plants. Gardens that are
broken up by internal borders, or with hedges, seem to
facilitate butterfly entry; large areas with close-cropped
vegetation serve as barriers for butterflies to fly over.
Ground cover such as clover, alfalfa, or other low-growing
host or nectar plants combine well with grasses in open
areas, and are much preferred over immaculately manicured
lawns, which are biological deserts for butterflies. When
choosing which plants to include in a garden, consideration
should be given to those providing a succession of blooms
throughout the entire growing season (i.e., early bloomers
like Spring Beauty and Lilac, middle season species such as
hawkweed and phlox, and late-season bloomers like butterfly
bush or asters). Several varieties of aster, both native and
cultivated, serve as host plants for pearl crescents
and checker spots, and nectar plants for many other species,
including sulfurs, monarchs, and swallowtails.
Stock wildflower mixes are commercially
available, some designed especially to attract butterflies
and other wildlife. In large yards, a portion of lawn could
be rototillered, and a small meadow established, with the
dual benefits of attracting more butterflies while requiring
less maintenance. Landowners could conduct garden surveys noting butterfly
species seen and plants grown, to determine for Nettle Lake
specifically which criteria are important in attracting
butterflies. This type of survey is currently being used in
Britain to identify factors associated with successful
butterfly gardens.
The goal of these measures is to increase
habitat quality and quantity for butterflies; and thus
increase both the total number of species using the area,
and the number of individuals of those species. If feasible,
further monitoring should be conducted in the future to
document species response to restoration efforts.
Another approach should address habitat
restoration/enhancement for species with narrow or
specialized larval food niche requirements not adequately
met at Nettle Lake. This would include species such as the
Zebra Swallowtail, the Spicebush
Swallowtail, and the Fritillaries. All of these species are adequately
cosmopolitan in their use of nectar plants, thus habitat
enhancement is needed most for host species. The Zebra
Swallowtail’s only known hosts are pawpaws, and its rarity
in northern Ohio is generally thought to be reflective of
the decreasing abundance of this shrub throughout the
region. Many populations in northern and central Ohio
inhabit small second-growth woodlots, and the absence of
pawpaws at Nettle Lake suggests a strong possibility of why
Zebra Swallowtails were not observed in the Biological
Survey. Thus, restoring pawpaws to deciduous forest patches
around Nettle Lake should be beneficial to Zebra
Swallowtails.
The Spicebush Swallowtail is another
species whose host plant(s) are apparently lacking or very
scarce at Nettle Lake. This larvae of this species are
reared on both sassafrass and spicebush. This is another
charismatic species that should benefit from the propagation
of its host plants.
The Giant Swallowtail is Ohio’s rarest
swallowtail. However, in good years, populations can be
locally abundant around swamps containing the primary host
plant. This primary host is prickly ash, but Giant
Swallowtails have also been reported to use hop tree. A
fine-filter approach to restoring this species would entail
introducing one or the other of the known hosts.
The Fritillaries are an attractive group, and
most of the species native to northwestern Ohio use violets
as host plants. Three species were documented in the Survey Halberd-leaved
Violet, Common Blue Violet, and Downy
Yellow Violet.
.
However, the precarious status of two of
the fritillaries, the Silver-border
Fritillary, is currently
state-threatened, and Speyeria idalia, the Regal
Fritillary,
is currently state-endangered, and is considered to be
deserving of federal listing warrants trying to enhance
habitat for the larval stages. The Regal Fritillaiy has only
been found and reared on birdsfoot violet in Ohio, though
other violet species are undoubtedly used. Birdsfoot violet
is a wildflower available commercially, and including them
in local butterfly gardens should potentially benefit most
of the native Fritillaries.
Naturally, nettles are present at Nettle Lake,
but given the suite of species for which they are either
obligate or facultative hosts, encouraging their growth
should benefit these species. The most common habitat
associated with these three butterflies is open areas next
to deciduous forest, such as old fields, orchards, forest
margins, roads, stream banks, and parks. Nettles could be
introduced to these types of sites that are sufficiently
distant from human use, so that they would not be considered
a nuisance. Similarly, other species that may not be
appropriate for formal gardens but are excellent at
attracting many species of butterflies, and would be
desirable in wild patches are the milkweeds, dogbanes,
goldenrods, and Joe-Pye weed. Although listed under Ohio’s
noxious weed law, Canada thistle is nonetheless also
attractive for a wide variety of butterflies.
The Purplish Copper, although currently
designated as state endangered, is most frequently
documented in northwestern Ohio. It often flies with
Lphlaeas, the American Copper, and is thought to be more
widespread in western Ohio than records indicate. For this
species, both host plants smartweed and docks and adult food
plants broad-leaved arrowhead, red clover, and swamp
milkweed are present at Nettle Lake. This species inhabits
marshy fields, borders of ponds and lakes, and other moist
places, and undoubtedly both wetland drainage and herbicide
use have negatively affected its populations. Because Nettle
Lake currently has both host and nectar plant species, this
is a butterfly species that might well occur there, but
requires further censuring to document its presence at this
site.
The two-spotted skipper is another state
endangered species, with very little known about its life
history. In Ohio, it is found associated with dense stands
of Carex stricta, and the larvae likely feed on several
other sedges. Swamp milkweed is a potential adult energy
resource found at Nettle Lake, but this species commonly
visits blue flag in Michigan. Thus Iris might be a
worthwhile species to introduce to wetland areas to attract
individuals of this skipper. Because Euphyes is another
easily-overlooked species, and likely occurs at low
densities, further monitoring is required to determine its
status at Nettle Lake.
The Karner Blue Butterfly has received
widespread attention because of its current status as
federally endangered. Although once extending from southern
Wisconsin to central New Hampshire, populations are highly
localized around its primary host plant, wild lupine. The
decline of this butterfly is attributed mostly to
uncontrolled succession in its specialized habitat, as a
result of fire suppression, and in Indiana, overuse of
recreational vehicles has also been implicated as a
contributing cause of its population decline. Currently, no
known viable populations occur in Ohio, but the Toledo Zoo
is experimenting with captive breeding and release of
individuals in the Oak Openings of Lucas County - the only
county from which any known specimens have ever been
collected in Ohio. Recently, The Nature Conservancy, in
cooperation with the Toledo Metropark system, has begun an
aggressive management program with periodic burning in an
attempt to maintain the early successional habitat upon
which the lupine depends. This program has the potential to
help the reintroduction of the Karner blue, and other
lupine-feeding butterflies native to Ohio still present but
declining. Although Lucas County has the only recorded
specimens of the Karner Blue from Ohio, this species has
been collected in all the northern counties of Indiana,
except Steuben County. If this species were ever
successfully introduced into Oak Openings, having lupine
habitat available in Williams County might be important in
the metapopulation dynamics of this species, by facilitating
dispersal and gene flow between populations. However, this
would require both having the large stands (Ca. one-half of
an acre or more) of lupine that the species apparently
needs, and active management to maintain them, which may or
may not be feasible or desirable at this site. An alternate
approach might be to have landowners include lupine patches
into their landscaping around Nettle Lake, which should
benefit the other two declining species that also feed on
lupine.
Butterfly and skipper species documented at Nettle
Lake, Williams Co. Ohio, May 9 1995 -Oct. 31 1996.
Hackberry Butterfly
Common Wood Nymph
Alfalfa Butterfly - Orange Sulfur
Clouded Sulfur - Common Sulfur
Monarch
Viceroy
Little Wood Satyr
Mourning Cloak
Tiger Swallowtail
European Cabbage White
Hobomock Skipper - Northern Golden Skipper
Great Spangled Fritillary
Red Admiral
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