I am Sibylla Brown. I was born in Germany in 1940. In 1946 my father, a German Operation Overcast scientist, was brought to the U.S. My family followed him to the U.S. in 1947, settling in Cedar Rapids Iowa in 1950. I married my husband, Bill in 1962. Bill practiced dentistry in Des Moines for over 40 years. In 1993 we sold our house in Des Moines and moved to a 200 acre farm in Decatur County, Iowa. Except for a small vineyard we had no plans to farm our land. But we did want to take care of it, particularly the overgrown oak and hickory woodlands. We began timber stand improvement in 1993. When we learned our land was actually a rare oak savanna remnant we implemented prescribed fire. These posts share how we found the land and how we made the transition from city-dwellers to country folk.
In the past couple weeks Bill and I made several butterfly forays to the property south of our fence line. There we followed the wide trail that winds through oak and hickory woodlands to a constructed wetland along the Weldon River bottom. We call the trail Butterfly Alley because this is where we always see the first mourning cloak of the season and is a good spot to observe giant and tiger swallowtails as they glide among the treetops. We’ve also seen rare species such as the Zabulon skipper there. Mountain mint and bergamot, two good nectar sources, are currently blooming on the trail and river bottom. Last week we also found a butterfly milkweed blooming at the woodland edge.
Besides the common summer butterfly species we saw a Horace’s duskywing feeding on mountain mint last week. According to Butterflies of Iowa this duskywing is an uncommon breeding resident, “scattered and rare throughout the state.” (Bill and I also see it at Timberhill every year.) So far the only other skippers we’ve observed on this adjacent property have been Silver spotted and Dun skippers. (At Timberhill we’ve identified 18 skipper species including the Byssus skipper, a rare breeding resident “restricted to native prairies.”)
For us time spent on unmanaged adjacent land is disheartening. Conservative native plants such violet bush clover are just hanging on in sunny openings. The woodlands abound in mature oak and hickory but are so overgrown that little sunlight penetrates the canopy. We see so much potential here. Yet these landowners are like parasites on the land caring only about how many big bucks and turkey gobblers they can shoot. They have complained about the dwindling deer and wild turkey population on their property. They don’t understand that everything is connected. That the game they are seeking thrives only in a diverse habitat. Just as the plants are winking out and sunlight is banned from the woodland the big bucks and turkey gobblers will find better habitat elsewhere.
After our last foray Bill and I decided to raise our spirits by watching butterflies in our south field which we began restoring in 1993. It’s just three acres but the abundance of bergamot, mountain mint, and common and marsh milkweed attract many butterflies. There we watched four Monarch butterflies dance among the swamp milkweeds. They glided from one bloom to another, moved off stage to sample the bergamot and then rejoined the corps on center stage. Occasionally two of them circled above the flowers in a pas de deux. Background music was provided by an Indigo Bunting singing from a nearby shrub. Watching the performance one would never know that Monarchs are in serious decline. They are thriving here.
I was stimulated to write this series because Bill and I have been told that “insects, eggs, or immature stages within the plants and the thatch cannot survive your burn regimen.” I was hoping to convince the doubters that invertebrate diversity is increasing not decreasing as a result of our management. Watching the Monarch ballet I realized that what others think of our fire management doesn’t really matter. We know it is working.
One of the most important features of Timberhill is that it isn’t in the middle of a corn desert. Although there are some crop fields on adjacent properties all owned by non-residents and are managed for deer and turkey hunting. This month Bill and I have been made several trips to the property east of Brush Creek, our east property line. A typical southern Iowa landscape of rolling hills and valleys that branch off the ridgeline it is similar to our West Creek unit. Both have bottom fields along a creek, prairie remnants, and were formerly pastures.
We surveyed the butterflies in a 30 acre former pasture that has been in CRP for over 10 years. The ridgetop meadow is bordered by Pony Farm Road on the north and east and woodland on the west. Large clumps of crownvetch dominate the ridgetop but branches that extend off the ridgeline into the surrounding woodland are scattered with conservative native plants including purple prairie clover, rattlesnake master, and panicled tick trefoil. Sedges, Indian grass, and winged loosestrife are also abundant there.
For butterfly observation there is abundant common mountain mint, wild bergamot, dogbane, and common milkweed, all preferred nectar sources. . There are even a few Sullivan’s milkweed plants just off Pony Farm Road. (an uncommon milkweed). We have observed all the common species, the Cabbage whites, sulphurs, Pearl crescents, and Great spangled fritillaries. Most abundant are the Great spangled fritillaries which is also true of Timberhill. We have also seen a Tiger swallowtail feeding on Sullivan’s milkweed. So far Dun skippers are only skippers we found. I saw a coral hairstreak, not a common species, perched on shingle oak. Best of all was a Juniper hairstreak, a species I have never seen at Timberhll, feeding on mountain mint near a red cedar. (We cut down all the red cedar, its larval food plant on our property.)
However, so far we have not found any Regal fritillaries, Edward’s hairstreaks, or Dion skippers, three species which we regularly see in the West Creek unit. Regal fritillaries are strongly habitat dependant limited to native prairie remnants. Their larvae overwinter in leaf litter. We don’t know whether they overwinter on our property, the adjacent cornfield, or small prairie remnant heavily infested with red cedar to the north. The Dion skipper is restricted to wetlands and usually found in northern Iowa. The Timberhill population is the only record of this species in Decatur County. Edward’s hairstreaks are confined to low growth scrub oak habitats with nearby ant colonies (Formica integra). Larvae are tended and protected by the ants in exchange for their sweet secretions.* This species is concentrated on a hillside with scrub shingle oak and native prairie.
Despite our prescribed fires population of these species has increased in the West Creek unit. Last month I saw five Edward’s hairstreaks in an hour. I usually see a Regal fritillary each visit. The Dion skipper is now regularly encountered in the sedge meadow that borders the wetland.
*Rick Cech and Guy Tudor. 2005. Butterflies of the East Coast. Princeton: Princeton University Press.
The best moth collecting usually coincides with the dark of the moon. Fortunately we had a few nights shortly after the new moon June 16 when rain did not threaten and we could set up our moth lighting in the East Savanna and on adjacent unmanaged property. On the adjacent property we used a moth trap constructed at the local welding shop. It consists of a funnel in a hardware cloth cage with a removable bottom. A black light fluorescent tube is suspended from a plant hanger attached to hoops on top of the cage Moths attracted to the black light fall through the funnel into the cage. they usually perch to the sides of the cage. The next morning we list and inventory the specimens. The specimens are then released.
The site most similar to conditions in the East Savanna is a wide opening in the oak and hickory woodland south of our property line. The first night the trap filled with geometer and three blinded sphinx moths. The second night there was more diversity, In addition to the geometer moths we collected two Luna moths, a Little virgin tiger moth (county record), 3 yellow underwings, a Small eyed sphinx (2014 county record), an Io moth (2014 county record), 2 more Blinded sphinx (county record), and one Giant leopard moth (2014 county record).
We collected the same species in East Savanna. In addition a luna moth, a twin spotted sphinx, two Imperial moths, several Isabella tiger moths, and a polyphemus moth were also attracted to that black light. And there was much more diversity with many small specimens that I did not identify.
Two species are of particular note: the Io and Imperial moths. In 2014 the Io moths I collected were the only collections of that species submitted to the Insects of Iowa website. So far this year we have attracted four specimens at Timberhill. This is a habitat sensitive species since the cocoons overwinter in leaf duff, under dry logs, or on hickory leaves. Finding them here indicates that the cocoons survive our annual dormant season prescribed burns.
The Imperial moth is another species in decline. Although it used to be common throughout its historical North American range it is in decline throughout the northeastern US. In 2014 the Insects of Iowa site listed only four sightings, two of which were in Decatur County (Lamoni and Timberhill). Imperial moth cocoons overwinter in underground burrows.
We will need to accumulate much more collection data to determine how our woodland management is impacting moth diversity. But the fact that we are finding rare habitat sensitive species at Timberhill is a good sign.
Michael M. Collins and Robert D. Weast. 1961. Wild Silk Moths of the United States. Cedar Rapids, IA: Collins Radio Company
(This growing season Bill and I are documenting as many breeding resident butterflies and moths as we can find and identify. In order to assess how our prescribed burns impact the Lepidoptera we are comparing our Timberhill collections to what we find on adjacent unburned woodland, wetland, and meadows. This will not be a list of all the species we see. Rather, we will focus on habitat sensitive species that spend their entire life cycle here. Neither of us is an expert lepidopterist but we hope to learn by doing. We identify our specimens by referencing various field guides and websites such as Insects of Iowa.)
Moth collecting centers on the use of lights. Although moths are attracted to existing lights on our buildings’ exteriors we chose to use portable lights that we can place closer to larval food sources. Our set up is supported by two poles that Bill had purchased to hang hummingbird feeders. At the chosen collecting site Bill inserts a screwdriver into a hole in the base of each pole, turns it, and screws the pole into the ground. A white sheet hanging from a clothesline strung between the poles is illuminated by two AC/DC fluorescent black light tubes which emit not only visible light but also the shorter ultra violet light that attracts moths. We power the lights with a portable rechargeable battery. We turn the lights on at dusk and monitor the sheet several times during the night, usually two hours after dusk, at 3:00 AM, and again just before dawn.
Spring is such a busy time that we didn’t begin our moth collecting until late May. We set up the light in East Savanna ridgetop. Surrounded by oak and hickory woodland this site is where we began our restoration and is our most diverse savanna with abundant stands of leadplant, cream wild indigo, and blazing star. Our first night was cool and when I checked the sheet at 10:30 PM all I saw were some beetles. But in the middle of the night numerous moths had settled on the sheet. Most interesting were a Blinded sphinx (Paonias excaecata) and a specimen I couldn’t identify. It was very distinctive: black speckled gray forewings with two white cell spots and rose colored hindwings. I assumed it was a owlet because it held its wings rooflike at rest. When I realized that I was stumped I guessed that I must have overlooked something really obvious. I had. I had neglected to check for a proboscis, the long thin moth feeding tube. (Silk moths don’t have proboscides because they don’t feed.) I sent a photo of my specimen to an expert friend who easily identified it as the common Honey locust moth (Sphingicampa bicolor).
On the other hand I’m not surprised that I couldn’t identify this species. Coloration is highly variable; early broods are gray, later broods are reddish brown to reddish orange. It may or may not have white cell spots on the forewing and the wings may or may not have scattered black specks. And most important we don’t have any Kentucky coffee or honey locust trees, of its primary larval food sources.
Both species spend their entire life cycles here overwintering in the ground as pupae. And both are Decatur County records.
(This growing season Bill and I are documenting as many breeding resident butterflies and moths as we can find and identify. In order to assess how our prescribed burn impacts the Lepidoptera we are comparing the Timberhill collections to what we find on adjacent unburned woodland, wetland, and meadows. This will not be a list of all the species we see. It will be our observations of habitat sensitive species that spend their entire life cycle here. Neither of us is an expert lepidopterist but we hope to learn by doing. We identify our specimens by referencing various field guides and websites such as Insects of Iowa.)
The Timberhill butterfly season began on March 30, a sunny and breezy day with the thermometer reaching 72’ F. , when Bill and I saw a mourning cloak, a breeding resident that overwinters as an adult. He flew out of the managed woodland east of the trail as we walked south through Butterfly Alley, the trail that separates our southeast woodland from the neighbor’s unmanaged woodland. Broad and sunny, Butterfly Alley is always a good spot for butterflies, especially in early spring.
Our next sighting was on April 11, another warm and sunny day with 73’F. Pairs of spring azures flew overheard while single specimens settled on the rue anemone and spring beauty blooming east of the trail. Near a clump of gooseberry bushes bordering the unmanaged woodland we saw a gray comma. Another breeding resident this species also overwinters as an adult. I saw another specimen in the Timberhill south meadow the following day.
It was April 29 before we saw the first skipper – a Silver spotted skipper on the south portion of the trail with unmanaged woodland on both sides. As we walked north we saw a Juvenal’s duskywing perched on a dead plant stalk at the edge of the unmanaged woodland. Juvenal’s is an uncommon breeding resident of open oak woodlands and adjacent areas. (Oak is its larval food source.) Further north was a Common sooty wing, a common breeding resident.
The rest of the week we moved our butterfly search to Timberhill. We had seen silver spotted skippers there but would we find any Juvenal’s duskywings? We began our search in the prairie just south of the Hickory Grove. Like all of our prairie openings it is surrounded by mixed oak-hickory woodlands. On May 6 we saw four Juvenals and one Silver spotted skipper in this prairie remnant. Despite intermittent rain and strong wind gusts we saw two Juvenal’s and two silver spotted skippers in the east savanna ridgetop oak opening on May 7. We found a similar pattern in the Hidden Prairie where we saw four Juvenal’s and one Silver spotted skipper on May 8.
Our last sighting of the Juvenal’s skippers was on May 13 in the East Savanna ridge top. Bill noticed movement among the scrub oak in the center of the oak opening. Carefully Bill stalked and netted one of the specimens so we could identify the species. Instead of one specimen we found two Juvenals in the net. When we released them one settled on an oak leaf in front of us and the other flew swiftly away. A mating pair? Was she was laying her eggs in the scrub?
As we headed back to the house a giant swallowtail flew swiftly overhead. The summer season is about to begin.
Brock, Jim P. and Kenn Kaufman, Butterflies of North America.
Schlicht, Dennis W., John C. Downey, and Jeffrey C. Nekola, The Butterflies of Iowa.