Thursday, September 11, 2014

A Dazzling Early September Nature Ramble

Pilot black snake @ Matthews State Forest
Although many of our favorite birds have migrated south by late August and early September, there is a great profusion of insect life in the fields and meadows.  Thus this time of year I spend a great deal more time walking in grasslands than in the woods, which comparatively have much less life than open areas.  

Variegated fritillary
On our 107 acre farm we have about 40 acres of former pasture which are now managed as grasslands which have been mowed, burned and planted in a heterogeneous fashion to yield a diversity of habitats.
Monarch butterfly nectaring on milkweed flower

Our common milkweeds were mowed along with the hay on July 11, but by Sept. 3 had re-grown and were even blooming.  Adult monarchs were nectaring on the flowers and laying eggs on the tender young leaves.  Our goal is to maximize the number of caterpillars such as this large one shown feeding on common milkweed. 

Monarch caterpillar on milkweed
Monarch caterpillars can sometimes be difficult to find so I  look for chewed leaves and  frass (caterpillar poop).  The caterpillars tend to hide when not feeding perhaps to minimize predation.  One unexpected potential predator was a large wheel or assassin bug on a milkweed plant;  these bugs are infamous for their painful bites so do not touch!  

Wheel or assasin bug at farm field
Some butterflies in the field were the beautiful sleepy oranges which fly low and often sit on the ground, and a variegated fritillary sipping nectar from a purple coneflower.  A somewhat unusual sight was a pair of mating yellow collared scape tiger moths.  Ours are more orange collared than yellow, and appear to be mimicking wasps as a means of defense.  Of course moths generally fly at night and are not usually attacked by day-feeding birds unless these avian predators can find the moths while they are resting on vegetation.  Tiger moths which fly in daytime may be either wasp mimics or have hind-wing flash colors to intimidate birds or warn them of toxicity.  

Yellow collared scape moths mating at the farm
Another invertebrate predator often found in the fields is a dragonfly, in this case a female widow skimmer.  The females are duller in color than the males and are often found away from water, thus avoiding competition for food with the males which maintain territories around ponds.  I also encountered a young pilot black snake prowling in the grass, looking possibly for a mouse or young bird to eat.

Widow skimmer (female) in farm field
Except for migrants passing through and a few hardy residents, our birds have abandoned us and have become "snowbirds" heading to southern climates.  This is a great time to learn the butterflies and some of the other myriad of insects that still throng the sunny meadows.  

Bill Dunson , Galax, VA and Englewood, FL
Sleepy orange butterfly

Monday, September 8, 2014

The Incredible Flight of a Willow Flycatcher

Harrison Illinois to Minatitlan Veracruz:
flight distance 1378 miles

Willow flycatcher

Willow flycatcher feeds 3 babies in nest
at Dunson farm, VA
We have perhaps four pairs of willow flycatchers breeding near our house in VA and recently were able to document two nests in red twigged dogwoods.  This constitutes a new record for late summer breeding for VA and allowed us to get some additional insight into the breeding habits of this uncommon flycatcher.  Our last indication of willows in the area was approximately the end of August.  The second nest fledged about Aug. 20.  So we were very interested in the report below about a willow flycatcher banded in Harrison, Illinois, Aug. 30, being recaptured in Minatitlan, Veracruz, Mexico two days later.  We do not have the exact times of capture nor do we know the flight track taken by this migrating flycatcher.  But assuming a 48 hour flight directly from Illinois to Veracruz crossing the Gulf of Mexico this yields a distance of about 1378 miles with an average flight speed of about 29 mph!!!  For such a tiny bird this is simply a remarkable feat of endurance, even if it were lucky enough to get a tail wind to reduce its energy expenditure from flying.  This is an another example of how little we know about the amazing migratory feats of birds which travel twice a year from South to North America. 

Bill Dunson

Sleepy orange butterfly color variation is confusing‏

When you are trying to learn how to identify the butterflies, variation among one species can be very confusing.  For the sulphur butterflies, all those yellow and orange ones, this difficulty is magnified if a single species varies in color.

Books report a seasonal variation in the color of the sleepy orange butterfly, found from southern PA to FL, from bright yellow-orange in summer to a dull winter form.

Here on our VA farm even in summer we have considerable variation between the classic bright form and a much duller color form.  Since this is a butterfly that flies low to the ground and often alights on ground vegetation, this color difference may have some significance in terms of camouflage and in breeding/attracting a mate.  Perhaps the brighter form is more successful in mating but gets eaten more often by predators?

For example here are butterflies photographed between Sept. 1-3.  Compare the bright form on green grass and the dull form against a mottled leaf.

By the way plant Cassias/sennas as a food plant for this beautiful insect.  So is it coincidental that a yellow butterfly feeds on a yellow flowered plant?

Bill Dunson

An Old Field Bonanza of Life

Old field at Matthews State Forest
Sometimes you are surprised by the abundance of life in an unexpected place. 

Ragged fringed orchis
One such paradoxical reservoir of biodiversity is the old field, perhaps thought of as a neglected former pasture or hayfield, or a place where low nutrients and poor soil make agriculture marginal.  Yet where it can be difficult or impossible to grow crops,  wildlife may thrive.  Poor soil especially makes it possible for some species of orchids to occur that do poorly against competition with grasses.  While attending a workshop at the Matthews State Forest, near Galax, VA, I happened to see an unusual orchid blooming, the ragged fringed orchis, Platanthera/ Habenaria lacera, in a small old field that had been preserved among some hayfields.
Orchid spiranthes vernalis
I did a careful inspection of the field one morning and found to my delight two more orchids, one uncommon (Spiranthes vernalis = spring ladies tresses) and one common (Spiranthes lacera v. gracilis = slender ladies tresses).   Orchids produce numerous tiny seeds that need to establish a symbiotic relationship with a fungus to successfully germinate and grow.  Thus their occurrence often seems to be ephemeral and hard to predict. 
Monarch butterfly
While surveying this field for orchids early one morning I was amazed to find a wide diversity of insect life.  For example there was a monarch butterfly apparently sleeping in the field.  As it warmed up a meadow fritillary, an eastern tailed blue and a Peck's skipper were flying about the field.  The blue is interesting since it has a false head on the rear of the wings with fake antennae and eyes; this arrangement in hairstreak butterflies has been found to deflect the attacks of predators, such as jumping spiders, away from the vulnerable head.  
Meadow frittilary

An even more striking insect, the yellow collared scape moth was also present. This tiger moth is apparently protected by its strong resemblance to a wasp, allowing it to be active in daytime.  Lurking among the vegetation there was also a well camouflaged praying mantis, the tiger of the Lilliputian world of the old field.

Peck's skipper, male
Within this old field there were several different "zones" which were distinguished by the primary vegetation present.  The upper zone on the right in the photograph had isolated clumps of little blue stem grass and this is where all of the orchids occurred.  
To the left and lower on the slope there were fewer bluestems and many purple topped grasses.  Lower still there were dense growths of goldenrod, with additional changes as one approached a creek in the valley below.  The association of the orchids with little bluestem is intriguing since we have found on our farm that this native grass seems to grow primarily on impoverished soils; it does not compete well with other grasses.

Eastern tailed blue butterfly
So in this neglected area of old field, there were two rare orchids, and a cornucopia of insect life that dazzled my mind.  Long may this old field survive and provide a refuge for rare plants and life of all kinds.

Bill Dunson 

Yellow collared scape moth
Praying mantis