Tom Peterson
November 1, 2003
The diversity and abundance of butterflies and birds seen here at Fermilab are a testament to the extent to which Fermilab has become an environmental refuge in the heart of one of the most rapidly developing suburban areas in the U.S. While casually watching butterflies here during my 27 years at Fermilab, and especially while more intensively surveying the butterflies for the past five years, it has been a joy to find several relatively rare (for northeastern Illinois) species, such as the Purplish Copper, Meadow Fritillary, and Dion Skipper, not only surviving here but thriving and moving into new areas.
Summary for 2003
No new butterfly species were seen at Fermilab in 2003, the second
year in a row that no new species were found. Although it is still
likely that strays providing new sight records will occasionally wander
through, and perhaps even a local population not yet identified at Fermilab
is hiding somewhere on site, the observations for the past five years have
given us a rather complete picture of the Fermilab butterfly fauna.
A cool, wet spring may have contributed to a slow start for the butterfly
season.
Cabbage Whites and Clouded
and Orange Sulphurs especially seemed
scarcer than usual from April into June, and the Sulphurs were never very
numerous. However, at the end of the summer there was a huge number
of Painted Ladies, and we also had large
numbers of Purplish Coppers and Meadow
Fritillaries. We are seeing interesting shifts in the population
centers for both the Meadow Fritillaries and Purplish Coppers. Both
species seem to be quite opportunistic, moving into old fields with their
larval host plants and nectar sources for the adults. I conclude
with a few recommendations to the ELM committee.
Some highlights for 2003
Big Woods
In March and April, Eastern Comma
winter forms and Mourning Cloaks were
flitting around together in the middle of the Big Woods. These butterflies
overwinter in the woods as adults and finding them in the early spring
is always a treat. As usual, the three anglewing species--Question
Mark, Eastern Comma, and Gray
Comma--were found in and near the Big Woods. The emergence of
a Giant Swallowtail from a
chrysalis that overwintered in the woods at Fermilab demonstrates that
some individuals can survive the winters here. Giant
Swallowtails, Great Spangled
Fritillaries, and Banded Hairstreaks
appeared at the woods edge in good numbers. The savanna-like area
west of the woods is consistently, every year, excellent butterfly habitat.
Encouraging a blending of woods into prairie via a savanna-like area, rather
than a sharp woods-prairie edge, will benefit these and many other butterfly
species.
Dion Skippers at Indian Creek
and on the east side of the site
In 2001, I mentioned that Ron Panzer, a Chicago area naturalist, reported
seeing Dion
Skippers along Indian Creek in the late 1980's and that the Dion Skippers
are still there. The Dion Skipper is only found in relatively undisturbed
sedge meadows, including only a few sites in the western Chicago suburbs,
so it is quite an interesting find for Fermilab. In 2002 and 2003,
the Dion Skippers were very abundant near Indian Creek again. A volunteer
monitor for the Northern Illinois Monitoring Network surveyed the Indian
Creek area this year for the first time. These data, particularly
for the Dion Skippers, will help us monitor the long-term health of this
sedge meadow. The Indian Creek area is also host to large numbers
of Northern Pearly-eyes, which thrive
in the open, wet woods. A highlight for 2003 was finding several
Dion Skippers in the sedges on the eastern shore of the A.E. Sea, on the
eastern side of the Fermilab site, about 3 miles from the Indian Creek
population.
Main Injector Wetland Mitigation
Dion Skippers have moved into the wetland mitigation! The sedge
meadow in the mitigation area appears healthy, with appropriate water levels,
and the presence of the Dion Skippers confirms that the mitigation is doing
well. The Main Injector wetland mitigation area also hosted Bronze
Coppers,
Acadian Hairstreaks and
Delaware
Skippers.
Meadow Fritillaries
Fermilab was full of Meadow Fritillaries
in 2003! In 2001, I found a colony of Meadow
Fritillaries living north and northeast of the garden plots, near ELM-20
(map).
Like the Dion Skipper, the Meadow Fritillary is not nationally rare, but
it is locally rare in the Chicago area. In 2002 and again in 2003,
with help from some excellent butterfly spotters in the Roads and Grounds
group, we found Meadow Fritillaries in various places on site. Starting
around May13 , many were flying along the power line and EJ&E railroad
right-of-way just north of the Batavia Road gate and also across C Road
from the Bison pasture. There seemed to be four peaks in Meadow Fritillary
numbers, perhaps corresponding to four generations -- May 15, June 24,
July 31, and September 11. This year we found especially large numbers
of Meadow Fritillaries at the old farm yard, site 70, on Wilson Road, and
also in the model airplane flying field. In fact, it seemed that
any open field with violets was likely to host Meadow Fritillaries this
year. A Pre-Service Teacher Intern counted both violets and Meadow
Fritillaries in a several places on site and found a strong correlation
between them; a higher density of violets meant a higher density of Fritillaries.
Was this just a boom year, or are they spreading into new habitat?
Meadow Fritillaries will continue to be a focus of our attention next year.
Silver-bordered Fritillaries
As was described in the 2002 butterfly report, on October 2, 2002,
Doug Taron introduced 40 Silver-bordered Fritillary caterpillars to the
Meadow Fritillary habitat on the east side of the Fermilab site.
Silver-bordered Fritillaries did not appear there in 2003. Doug Taron
thinks the caterpillars may have been too mature to hibernate. We
would like to try a release again but were not able to do it this year;
perhaps next year. Nevertheless, the release area, which again this
year included Meadow Fritillaries, is being monitored for the Northern
Illinois Butterfly Monitoring Network.
Bronze and Purplish Coppers
Good numbers of Bronze Coppers and
Purplish
Coppers were found this year, more than in 2002. Purplish Coppers
were widespread and persisted well into October. The presence of
fresh-looking individuals in October may indicate an autumn emergence,
a partial third or fourth generation. The Purplish Coppers were found
again in those new places for 2002 along Wilson Street, along Road A, and
along Road C. Large numbers of Purplish Coppers live in the wet meadow
south of the Main Ring. This area was in agriculture as recently
as about 10 years ago. The Purplish Coppers appear to be very opportunistic,
moving into relatively new areas that contain their host plant, which was
identified by Bob Betz as Polygonum coccineum here. Like for
the Meadow Fritillaries, the habitat where they were first found to be
extremely abundant several years ago is no longer the best place to find
them. There seems to be some shifting of the locations of population
centers, which will be interesting to continue to watch. Both Bronze
and Purplish Coppers seem to be quite widespread and well-established on
the Fermilab site; I doubt that any special consideration needs to be given
to mowing times for the various locations where the Coppers have been seen.
In fact, the management method followed for the past several years seems
to be working quite well for the Coppers. On September 17, Doug Taron and
I collected four female Purplish Coppers to provide a source of young larvae
for a possible introduction elsewhere in Illinois. Thus, not only
may Fermilab be the recipient of a butterfly introduction, like last year
with our Silver-bordered Fritillary attempt, but Fermilab may provide "seeds"
for other introductions. Both
Bronze and Purplish Coppers seem to be quite widespread and well-established
on the Fermilab site and are highlights of the butterfly season here every
year.
Conclusions
1. My strongest recommendation to the ELM committee remains the
same as last year: we should encourage savanna-like transition zones
between our prairie restorations and adjacent woodlands. With the
Arbor day planting just west of the Big Woods, we are doing exactly that.
2. The Main Injector wetland mitigation looks healthy and is
hosting a variety of wetland butterflies including Dion Skippers and Bronze
Coppers.
3. The Silver-bordered Fritillary introduction did not seem to
work. We may try that species again and/or may try other species
eventually, as well.
4. Two areas at Fermilab are now being monitored as part of the
Northern Illinois Butterfly Monitoring Network database, the Dion Skipper
habitat along Indian Creek and the Meadow Fritillary habitat along the
EJ&E tracks northeast of the garden plots.
5. Meadow Fritillaries and Purplish Coppers, both relatively
rare species in the Chicago region, are proving to be very interesting
subjects of study at Fermilab. Although very widespread and well-established
on site, their locations of greatest abundance seem to have shifted over
the past several years. Observations here indicate that neither species
is particularly "remnant-dependent", but rather quite opportunistic in
moving into new habitat with their larval host plants, even rather disturbed
and weedy areas. Fermilab's management of old fields with approximately
annual mowing allows the host plants (violets for the Meadow Fritillaries
and Polygonum species for the Purplish Copper) to thrive among nectar
sources like clover, thistle, daisies, and asters. These two species
in particular will merit close observation in the upcoming years.
6. The proposed Eola Road corridor on the east side of the Fermilab
site includes the following species that are limited to wetland remnants:
Bronze Copper, Eyed Brown, and Dion Skipper. It also includes the
only Coral Haristreak population that I have found on site and is a major
habitat for Meadow Fritillaries.
