Category Archives: Fauna

Learning from Nature

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Each summer when I see Turkey vultures ride into the sky on thermal updrafts and soar overhead it takes me back to my childhood and learning from nature with my father, aircraft designer Alexander M. Lippisch.  Best known for the ME163 rocket fighter, Lippisch was inspired by nature for most of his unconventional aircraft  designs. The swept wing tailless ME163 rocket fighter, for example, was based on the delta shaped seed pod of the Javan cucumber, Zanonia macrocarpa, that an uncle had given him.

While Lippisch was working for the Office of Naval Research (leave it to the government to assign an expert in supersonic flight to design boat hulls) he met aerophysicist Dr. August Raspet.  A highly skilled sailplane pilot,  Raspet spent many hours in gliders. But no matter how skillfully he was able to glide his way among the air currents it was never as well as the ever present turkey vultures.  Their  ability to soar and maneuver through the air far surpassed his sailplane’s performance.  Lippisch had also observed these birds and was fascinated by how they used air currents,  floating lazily, banking and turning at will with never a wing flap.  Both men were interested in studying  bird flight to determine if application of its principles could be applied to the design of conventional aircraft.

“Your observation on the Turkey Buzzard (vulture) is very interesting. Had I completed the performance measurements of the Buzzard which I tried several years ago we could have analyzed the data to determine the effective aspect ratio.” (Raspet to Lippisch letter, 10 March, 1948.)

This shared interest resulted in a productive collaboration.

Turkey vulture in flight

Raspet  began his measurements of Turkey vulture flight performance in 1949, after being appointed director of the Department of Aerospace engineering at Mississippi State University .  He followed the birds in his sailplane comparing their performance in spirals,  relative climb rates,  as well as cross-country straight flights.   In order to make actual measurements of the difference in performance between the sailplane and bird, a camera in the nose of his sailplane filmed  bird flight  and a ground observer filmed the sailplane.  The soaring speeds of the birds during spiraling flight could be measured against that of the glider  by evaluating the films.

“On my Kite [Kirby-Kite sailplane] I get the real soaring effect by flying right at stall and letting the ship wallow in and out of lifting zones.  Recently I followed a buzzard at 800′ all over the area in this manner.”(Raspet letter to Lippisch, 2 April, 1949.)

After analyzing measurements of the wild bird’s flying skills Raspet wondered whether  ”feathers are necessary on a sailplane.”

Correspondence between Raspet and  Lippisch  discussed  how the analysis of Turkey vulture flight could be applied  to tackle two of the major problems of conventional aircraft design: how to maintain a smooth (laminar) airflow over the wing surface and how to reduce the major drag induced by the whirling mass of air flow (vortices) over the wing tips.  From Raspet’s measurements and observations they learned  that vultures change the shape of their wings to maintain a smooth (laminar) flow of air over the wing surface. This increases lift and  reduces drag. Regarding the wing tip vortices Raspet wrote,

“In fact, it can happen that the tip feathers actually reduce the tip losses to a point where the complete planform of the wing is aerodynamically active.” (Sailplane Project of Mississippi State College”, p. 3)

Turkey vulture using slotted wing tips increase lift and reduce drag

Based on these observations Lippisch proposed use of small wings or wing slots to recover the energy lost at the wing tips of conventional aircraft.  He received a patent for this design in 1956.

(From Henry V. Borst, The Aerodynamics of the Unconventional Air Vehicles of A. Lippisch. 1980  )

Raspet ‘s research resulted in his receiving a long term federally-funded program to study how laminar flow could be achieved in low-speed aircraft and the application of composite materials in aircraft design. Tragically, he died in the crash of a Piper Cub demonstrating boundary layer modifications on April 27th, 1960.

 

 

 

 

 

Buckeye Butterflies Breeding at Timberhill

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Common Buckeye

One of the most common butterflies at Timberhill is the Buckeye (Junonia coenia), a medium sized brown peacock butterfly. Distinguished by the bold pattern of eyespots, white bars and orange cell bars on its wings this species is  found throughout the United States (except the northwest) but is most common in the southern states.   Buckeyes do not overwinter in Iowa and specimens seen here are ones that have migrated north from the south in late spring.  It is presumed that they migrate south in the fall.  The description in Butterflies of Iowa poses the question do they breed in Iowa? They do at Timberhill.

In order for butterflies to breed a site must have the plants the larvae feed on.  Of those preferred by Buckeyes Bastard toadflax, wild petunia, and slender false foxglove are all abundant at Timberhill.   In late August and September  the longitudinally striped caterpillars with their pattern of branching spines were easy to spot feeding on slender false foxgloves, Agalinis tenuifolia.  These annuals are stimulated by fire and are particularly abundant in the old corn field in our West Creek unit.  Large clumps bloom throughout the field  in late summer.

Buckeye larva on slender false foxglove

Below is a photo of the hard outer shell of a Buckeye chrysalid from which an imago, the perfectly formed butterfly, emerged in September, 2011. Buckeyes have 2-3 broods between May and October.    The chrysalid stage lasts only two weeks in the fall. Presumably that gives the adult stage plenty of time to head south.  However, we were still seeing occasional adult specimens as late as November 4.  Shouldn’t they have headed south by then?

Buckeye chrysalis

LASIOGLOSSUM VERSATUM: DIVORCE BEE STYLE

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On a recent sunny day Bill and I had the unexpected pleasure of following naturalist Laura Rericha on walk through our restoration.  Laura and Dr. Gerould Wilhelm were co-authors of the 2007 Timberhill Savanna:  Assessment of Landscape Management.   It was by watching and listening to them in the field that I  gained a true understanding of savanna restoration.

Laura and Jerry’s first visit to Timberhill was in 2003, ten years after Bill and I had begun restoring Timberhill.   Although we were having excellent results from our management, others were highly critical of our methods.  We were told that we should be planting savanna indicator species, and that we were burning too frequently at the wrong time of year.   In any case it didn’t  matter since everyone knew there were no oak savanna remnants worth saving in Decatur County, Iowa.

Thanks to Jerry and Laura that has all changed.  On his first visit in June, 2003, Jerry noted 206 native vascular plants.   (Finding 180 species in a single survey usually indicates a high quality remnant.)   When Laura surveyed the ants for the Timberhill study she identified fifty two species, two of which were new to the Iowa list.  (The Iowa lists contains 100 species.)    Laura and Jerry’s work  gave Timberhill legitimacy.

On her own initiative Laura has mastered  ornithology, botany, and myrmecology.  Her current research is surveying the native bees of the Midwest.    Wild native bees such bumblebees and sweat bees evolved with the plants they pollinate.   They are seriously threatened by loss of natural habitat. Currently  four dozen native wild bees are listed on the Xerces Society’s red list.

L. versatum worker bee looking for a home

Thanks to Laura, Bill and I were able to observe the behavior of Lasioglossum versatum  a greenish black sweat bee that nests in the soil.  She pointed out swarms of Lasioglossum versatum workers circling over and around small holes in the soil.  The holes were entrances to an aggregation of L. versatum nests that spread over the trail and into the adjacent woodland.

From a small entrance (3-5 mm.) in the soil the nests extend underground through tunnels  with  branch burrows and individual cells for  eggs and larvae.  Several fertilized queens hibernate in each nest during the winter and will produce the next generation the following spring.  (They do not tunnel new nests each year.) As winter approaches the queens must prepare for propagation of their species.

When they sense cold weather approaching the queens drive the worker bees out of the nests.  After hard frost there will be no more flowering plants to supply the bees’  pollen.   To survive diapause with enough food for the larvae the queens must drive the workers out of the nests.    Fascinated we watched the worker bees frustration as they swarmed over and around the nest aggregation.  Whenever a worker came close to nest entrance a  queen’s head moved into the opening, blocking the hole.    The queens will continue to guard the nests until there is no longer any threat of the workers returning.

L. versaturm queen blocking nest entrance

Were we to follow the  protocol of burning every three years we would probably not have been able to observe this drama.  The ground would have been covered with leaf duff, obscuring the nest entrances.  Would Lasioglossum versatum even be nesting here if the ground was covered with dead leaves?

 

Reference:  Charles D. Michener. “The Bionomics of a Primitively Social Bee, Lasioglossum versatum (Hymenoptera: Halictidae).  Journal of the Kansas Entomological Society. Vol. 39, No. 2 (Apr., 1966), pp, 193-217.

Waterbirds at Timberhill

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Ten years ago I was while doing spring garden work, I heard a loud splash from the pond west of the house. I turned around and looked down on the water.  There was a huge flapping of wings then an osprey took off from the pond surface.  His claws clutching a fish he headed for a dead oak tree south of the pond, landed on the uppermost branch and began eating his prey. Ospreys are a common site in Florida Bay, but in a small Iowa  farm pond?  It was a delightful surprise to observe this large raptor.  For a couple weeks, Bill and I watched him make daily visits to Timberhill pond.  He would hover over the pond eyeing his prey, dive feet first to the water, grab a fish near the surface, then dispose of it in a nearby tree. Every April since than an osprey has returned to Timberhill on his way north to larger waters.

Osprey eating his prey

Ours is a small pond, only about an acre in size, yet this small body of water attracts many birds.  Besides the osprey, a snowy egret, green heron, and several cormorants have stopped here this spring. Although these birds are a common site in U.S. coastal waters  it is a special treat to be able to watch them visit our pond. The pond also attracts season regulars: wood ducks from the adjacent woodland, great blue herons that nest on the Weldon River and belted kingfishers.

Egret visiting Timberhill pond

All summer long flocks of swallows patrol the pond for insects.  We call them our mosquito patrol and welcome them although they compete with the bluebirds for nesting boxes.  Even in the depths of winter birds are a constant presence at Timberhill. But the migrating waterbirds are a special pleasure.

Eighteen years ago when Bill and I began restoring Timberhill  we didn’t know what to expect. Each year as the ecological community continues to grow more diverse we are truly in awe of the power of nature to restore it’s essential character.  Our only responsibility has been timber stand improvement and annual dormant season burns.    Mother Nature does the rest.

 

BALD EAGLE FOOD

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For those of us restoring Decatur County oak savanna  one of the biggest problems is deer.  Not only do they eat the replacement oak sprouts, but flower buds of the most conservative forbs.  The more conservative the plant, the better they like it.  False hellebore (Veratrum woodii), lady’s slipper orchids and MIchigan lilies (lLilium michiganense – flower buds of these forbs all are  fodder for the hoofed rodents.  Of the hundreds of wild lilies in our West 40 unit, I’ve only ever seen one in bloom.  We can protect the yellow lady’s slipper orchids with hoops and deer netting but the false hellebores  and lilies are too numerous cover.  Instead we take advantage of  the January antlerless deer season to kill as many does as possible.

Two of our local friends do the hunting and usually kill about ten does each season.  They do their own butchering and return the carcasses to Timberhill to be recycled as bald eagle food.   Dumped in the border between the ridgetop prairie and the hickory grove west of the house  where Bill and I  can enjoy watching the bald eagles.

Bald eagles feeding on deer carcasses

When we first moved to Decatur County one of our neighbors told us he had seen an eagle nest along the Weldon River south of our property.  But we never expected to see  bald eagles on our property.  One thinks of their habitat primarily in the Pacific Northwest  and Alaska.  In Iowa I knew that they were found along the major rivers, but was surprised to see them in Decatur County each winter, especially during deer hunting season.

Deer take-out

Black crows descended on the deer carcasses almost immediately after they were unloaded.   The next morning I saw a bald eagle perched at the top of the tallest hickory overlooking the remains.  At mid-morning I watched him head-down, grasping at a chunk of bright red meat with his golden beak.  As the week progressed we saw more eagles.  By the end of the week we observed five eagles feeding at the same time as two immature eagles soared overhead.  One eagle decided not to share and took off with the meat clutched in his claws.

Immature bald eagle

The carcasses provide food for a number of other birds and mammals among them red-tailed hawks, raccoons, and coyotes.     By the end of March there will be nothing left but a few bones.

(Photos by Bill Brown)