Tom Peterson
November 10, 2003
Fermilab's 6800 acre site contains ecologically high quality habitat which has been carefully managed and protected for the past 35 years, including restored prairie, lakes, wetlands, meadows, and woods. The diversity and abundance of butterflies and birds seen here 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.
Some
highlights for 2003
No new butterfly species were seen at
Fermilab in 2003, the second year in a row with no new species. Although
it is still likely that strays providing new site 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 2003 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.
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 demonstrates that some individuals
of this species 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.
Dion
Skippers
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 May 13 , 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; more violets meant more 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 another release 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 Purplish Coppers 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. 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.
