Friday, September 5, 2014

September 4 2014 Ramble Report




We're back to our non-summer start time, 8:30AM, and 23 ramblers showed up for this comfortable morning.

Don Hunter's album for today's ramble is here.

Reading: Today's reading is an excerpt from an address given by Aldo Leopold at the dedication of a monument to the passenger pigeon. The last living passenger pigeon died in captivity 100 years ago this month.

We are told by economic moralists that to mourn the pigeon is mere nostalgia; that if the pigeoners had not done away with him, the farmers would ultimately have been obliged, in self-defense, to do so.

This is one of those peculiar truths that are valid, but not for the reasons alleged.

The pigeon was a biological storm. He was the lightning that played between two opposing potentials of intolerable intensity: the fat of the land and the oxygen of the air. Yearly the feathered tempest roared up, down, and across the continent, sucking up the laden fruits of forest and prairie, burning them in a traveling blast of life. Like any other chain reaction, the pigeon could survive no dimunition of his own furious intensity. When the pigeoners subtracted from his numbers, and the pioneers chopped gaps in the continuity of his fuel, his flame guttered out with hardly a sputter or even a wisp of smoke.

Today the oaks still flaunt their burden at the sky, but the feathered lightning is no more. Worm and weevil must now perform slowly and silently the biological task that once drew thunder from the firmament.

The wonder is not that the pigeon went out, but that he ever survived through all the millennia of pre-Babbittian[*] time.

*reference to the satirical 1922 novel Babbit by Sinclair Lewis

(From Aldo Leopold, On a Monument to a Pigeon, in A Sand County Almanac and Sketches Here and There, 1949, Oxford Univ. Press, p. 111 in the 1968 paperback edition.)

Each rambler received a printed sheet of paper that, when folded according to instructions, results in an origami passenger pigeon. After the ramble we folded our own miniature flock at Donderos'. Those of you who weren't able to attend today's ramble can obtain your own origami passenger pigeons from http://www.foldthe flock.org and while you're there view an awesome animation of what a flock of must have looked like as they passed overhead. 

To learn more about the passenger pigeon extinction read this Audobon magazine article and this NY Times article about the role of "social media" in the extinction. The August 29th NY Times Sunday review section had a nice article with interesting graphics depicting the abundance of the passenger pigeon over time.

Parasites that change their hosts behavior: Before we started I passed around a beech
Fungus infected spider
leaf that Emily and I found at the garden two days ago. On the underside of this leaf is the body of a dead spider. Sprouting from the abdomen are the fungal spore producing shoots, looking like the fingers of a dead hand. Fungi like this have been seen in other arthropods, especially ants. Infected ants leave their nest and climb up grasses and trees and then bite whatever they are on. They remain there, locked to the plant by their jaws until they die. Meanwhile the fungus is busy digesting their interior and sprouting its spore-dispersing structures into the air. The ants typically are anchored to a place that is favorable for the dispersal of fungal spores. We don't know if this fungus changed the behavior of its spider host, but it is a possibility.

Today's route: From the arbor down the walk through the Shade garden and into the Dunson garden, then across the road to the White trail, up the power line and then down the power line to the river; left on the orange trail past the privet removal project and then back to the arbor via the orange spur trail.

Shade Garden

On the sidewalk through the Shade Garden there were many hickory nuts that had been gnawed on by rodents. The large mockernut hickory nuts had very thick husks and some of their diners had given up chewing through the husk to get at the nut inside. The pignut hickory nut has a much thinner husk and we found several that had been successfully opened and the contents devoured.

We also stopped to check on the witch hazels. Earlier in the spring we observed numerous galls on the leaves of the native species (on the right side of the sidewalk if you're going downhill) and split a few open to reveal they were filled with aphids. Today the galls remain on the leaves but they are all empty. The aphids have flown away to an alternate host plant where they will feed and lay overwintering eggs. Next spring the eggs will hatch and the winged aphids will again seek out the witch hazel and produce a new round of galls on its freshly emerged leaves. Mark your calendars for next spring to see this exciting event.

Triangulate Orbweaver
While at the witch hazels we looked for the tiny flower buds that are just now forming. Witch hazel blooms late in the fall, so we'll be checking these plants often come October.
A rambler spotted a small spider web and at the center was the spinner, a brownish spider with a prominent bright yellow triangle on its abdomen -- a triangulate orbweaver.

Dunson Native Flora Garden

Horsebalm inflorescense
We ducked into the Dunson garden to check on the Horsebalm that we had seen last week. It is now in bloom and, if you were expecting a fantastic floral display, somewhat anti-climactic.
But standing next to the horsebalm was the stalk of a Jack-in-the-Pulpit, or, more precisely, Jill-in-the-Pulpit, bearing brilliant red fruits. Red is a common color of fruits that are bird
Jack-in-the-Pulpit fruits
dispersed. The plant offers the bird a sweet, red treat and the bird consumes the flesh that surrounds the seeds and then defecates the seeds somewhere else, along with a drop of fertilized to get them started. It's a win-win situation for both parties.
Some ramblers noticed a Downy Skullcap in bloom and when we started up the road we found a Beautyberry with its clusters of bright purple fruits.


White trail

Microstegium and Beefsteak plant
At the intersection of the White trail and road there was a patch of dense vegetation made up of two species: Beefsteak plant, a mint, and microstegium.

Microstegium (also called Nepalese browntop or Japanese stilt grass) is a terribly invasive annual grass. It can flourish in low light situations and displace native species. In addition to its direct effects and plant communities additional impacts have recently come to light. A recent study, published in the journal Ecology by two UGA researchers, shows that Microstegium has a negative impact on American toads. (You can read the paper here.) This study reveals that when microstegium invades a habitat the number of wolf spiders increases. Wolf spiders are hunters. They search their habitat for small arthropods which they attack, kill and eat. Their prey also include their own species and this cannibalism helps to reduce the size of the wolf spider population. So how does microstegium cause the number of wolf spiders to increase? Because a patch of microstegium is so dense, containing many stems, wolf spiders have a more difficult time finding other wolf spiders. So more of them survive in a patch of microstegium. This increase in spider density means that very small, recently metamorphosed toads are more likely to encounter and be eaten by spiders, so there numbers decline. This is an example of an "indirect" effect or a "knock-on" effect: A causes B to change and the change in B has an impact on C. Ecosystems are full of these kinds of effects. It makes knowing the effect of changing a habitat so difficult to determine.

Pulling Microstegium
Several of the ramblers immediately began to pull up the microstegium.

Further along the White trail we found examples of Smooth Sumac, Yellow crownbeard, River oats and purpletop grass.

How to tell the wingstems apart. Wingstems are plants in the genus Verbesina; we have three species in the natural areas of the garden: V. alternifolia, V. virginica and V. occidentalis. Distinguishing them is pretty easy, but sometimes difficult to remember. Here are the tricks I use to keep them straight.

Common Name
Scientific Name
Flower color
Leaf arrangement
Wingstem
V. alternifolia
Yellow
Alternate
Frostweed,
V. virginica
White
Alternate
Crown-beard
V. occidentalis
Yellow
Opposite



Wingstem
I have the most trouble associating the names with the combinations of characteristics, so I use a mnemonic: V. occidentalis has opposite leaves (opposite and occidentalis
Crown-beard
both begin with "o"; V. alternifolia has alternate leaves (this is easy since alternifolia means "alternate leaves"); V. virginica is named for Virginia which is further north than Georgia and, therefore, colder, so the plant has snow-white flowers and is called Frostweed. I haven't come up with a good way to remember that Wingstem has yellow
Frostweed
flowers, except by elimination (Frostweed is the only one that has white flowers, so if  the plant has yellow flowers it's either Crown-beard or Wingstem and you can tell them apart by their leaf arrangement. If you can remember all this it might help build new neurons in your brain. 

How do you tell if you're looking at a Verbesina? You need to look at the stem to see if there is a ridge running the length of the stem on opposite sides. Unfortunately, some of the Wingstems (using the term to refer to the whole group, not just V. alternifolia) have faint wings and some individuals have them only on the lower or upper parts of the stem. Plants are variable, so you have to examine the stem closely. Another characteristic of the group is that the flowers are pretty skimpy. That's because only some of the florets have a petal. Many of the florets are disk florets, and do not have the strap-like petal.

You had to be there: Some things in nature happen very quickly: a hawk attacks a bird on the feeder in your yard. You have to be looking out the window at the right time or you'll miss it. One of those events happened as I was walking with a couple of ramblers on the Orange trail in the privet clearing section. One of them called my attention to a large wasp that was hanging onto the end of a twig and behaving very strangely. I took a closer look and realized that I was
European Hornet with prey
seeing a European Hornet, a very large wasp that has become naturalized in the United States. It appeared to be holding something and I looked closer -- the hornet was grasping a small Yellowjacket in the legs that were holding the twig and it was manipulating the Yellowjacket to keep the sting away from its body. As I watched it bent down and bit the head off the Yellowjacket and immediately flew off. It had taken just a few seconds to subdue and kill the smaller Yellowjacket. European Hornets construct paper nests, like Bald-faced Hornets do, but they are built in cavities instead of on branches of trees. This Hornet was taking the Yellowjacket back to its next to feed it to the larvae that are communally raised in the nest.  The typical nest holds about 200-400 workers and a single reproductive queen. I'm sorry that not everyone could see this exciting sight, but it was over too quickly. (Photo of European Hornet with prey from Wikipedia.)

Upper power line right of way Today we saw many of the same plants we saw blooming last week, so I'm going to just list them here and write a little more about a few of them later:
Flowering Spurge, Wild lettuce, Beefsteak plant, Grass leaf Golden aster, Mountain mint, Rabbit tobacco, White crownbeard, Elephant’s Foot, Wild Sensitive Plant, Yellow star grass, Late-flowering thoroughwort (or boneset) and Slender ladies tresses.

Lower power line right of way The plants seen on the power line right of way between the road and the river were: Golden aster, Silver plume grass, Late-flowering boneset, American Pokeweed, Camphor pluchea, Spotted St. Johns Wort, Virginia button weed, Tall ironweed, Field thistle, Common evening primrose, Climbing Hempvine, Daisy fleabane, Goldenrod, Small white morning glory, Wingstem, and Leafy elephant’s foot.

The critters we saw were: Gulf fritillary caterpillar on passionvine, Gulf fritillary caterpillar in the act of forming a chrysalis; a Pearl crescent butterfly and a Carolina anole.
 
How a caterpillar forms a chrysalis. The pupal stage of a butterfly is called a chrysalis; that
Chrysalis half-way free from caterpillar skin
of a moth, a cocoon. A cocoon is usually covered with silk spun by the caterpillar and often has leaves or the hairs of the caterpillar imbedded in it. (Technically, the
Gulf Fritillary caterpillar
cocoon is the silken structure that surrounds the naked pupa of the moth, but the term is casually used in a collective sense to refer to both pupa and silken surrounding.) The pupal stage of a butterfly is naked, like the moth pupa, but it is often brightly colored and decorated or assumes cryptic shapes so that it resembles a dead leaf.  The chrysalis of many butterflies hangs head downward, suspended from a button of silk in which the posterior end is hooked. Several ramblers were lucky to catch a Gulf fritillary butterfly in the final stage of chrysalis formation . It begins with the caterpillar spinning a button of silk. The caterpillar then clasps the silk button with its terminal abdominal legs and hangs head downward, usually forming a J-shape. The pupal skin forms under the caterpillars skin and then the caterpillar skin splits down the back. The pupa begins to wiggle and twist and gradually emerges from the old caterpillar skin. At this point the old skin looks like a sock being peeled off. With more wiggling it is gradually worked back to the point of attachment.
Cast off caterpillar skin
Then the pupa performs a complex maneuver -- it grips the old skin between its last few segments and wiggles the last segment free from the old skin. The skin is still hooked to the silk button and the pupa is gripping the skin, hanging from it head downward. The freed terminal segment has a hook on its end and this hook is jabbed into the silk button and twisted around enough to anchor the pupa. The pupa then releases the shriveled caterpillar skin. The skin usually drops to the ground and the pupa slowly transforms into the final shape of the chrysalis (It usually takes less than a day to complete chrysalis formation. The butterfly will emerge a week or two later.) 

Orange trail and Orange spur trail

It was getting late so we quickly turned left onto the Orange trail to see the amazing progress in Chinese Privet removal. Then we turned up the Orange spur trail to return to the Arbor, where we received our Origami Passenger Pigeon papers. Along the way we saw Ebony Spleenwort and our old friends, the Beech Blight Aphids.

We returned back to the Arbor and folded our flock at Donderos'.
Folding our flock

SUMMARY OF OBSERVED SPECIES:
Common Name
Scientific Name
Shade Garden
Witch hazel
Hamamelis virginiana
Pignut Hickory
Carya glabra
Mockernut Hickory
Carya tomentosa
Triangulate Orbweaver
Verrucosa arenata
Dunson Garden
 Northern Horsebalm
Collinsonia canadensis
Jack-in-the-Pulpit
Arisaema triphyllum
Downy skullcap
Scutellaria incana
Beautyberry
Callicarpa americana
White trail
 Japanese stiltgrass
Microstegium vimineum
Perilla mint or beefsteak plant
Peri indicutescens
Yellow crownbeard
Verbesina occidentalis
River oats
Chasmanthium latifolium
Smooth sumac
Rhus glabra
Purpletop grass
Tridens flavus cupreus
Upper power line right of way
 Flowering Spurge
Euphorbia corollata
Wild lettuce
Latuca spp.
Golden aster
Packera aurea
Mountain mint
Pycnanthemum incanum
Rabbit tobacco
Gnaphalium obtusifolium
White crownbeard
Verbesina virginica
Elephant’s Foot
Elephantopus tomentosus
Wild Sensitive Plant
Chamaecrista nictitans
Yellow star grass
Hypoxis hirsuta
Late-flowering boneset
Eupatorium serotinum
Slender ladies tresses
Spiranthes gracilis
Lower power line right of way
Gulf fritillary caterpillar
Agraulis vanilla
Silver plume grass
Saccharum alopecuroides
 American Pokeweed
Phytolacca americana
Camphor pluchea
Pluchea camphorata
Spotted St. Johns Wort
Hypericum punctatum
Dwarf St. Johns Wort
Hypericum mutilum
Virginia buttonweed
Diodia virginiana
Carolina anole
Anolis carolinensis
Pearl crescent butterfly
Phyciodes tharos
Tall ironweed
Vernonia gigantean
Field thistle
Cirsium discolor
Climbing Hempvine
Mikania scandens
Daisy fleabane
Erigeron annuus
Goldenrod
Solidago altissima
Gulf fritillary chrysalis
Agraulis vanilla
Small white morning glory
Ipomoea lacunose
Wingstem
Verbesina alternifolia
Leafy elephant’s foot
Elephantopus carolinianus
Ailanthus Webworm Moth
Atteva punctella
European Hornet
Vespa crabro
Yellowjacket
Vespula sp.
Orange spur trail
Ebony spleenwort
Asplenium platyneuron
Beech Blight aphids
Grylloprociphilus imbricator

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