Late Summer Nature in the Blue Ridge

August 30, 2018

Nature Notes by Bill Dunson

 

As the summer season progresses into the infamous dog days, which are historically associated with the rising of the dog star Sirius, nature undergoes some profound changes. Spring bird migration is over as is most breeding, fall migration has begun and little bird song is heard. Most amphibians have completed breeding. It is a time for insects, heat, and thought of the cooler fall days to come.

While the brunt of summer heat is minimized in the Blue Ridge mountains, we do have days in the high 80’s and such heat favors the activity of butterflies and other insects. This is a good time to learn the butterflies, especially the difficult “black and blue mimics.” As some examples can you distinguish the toxic model pipevine swallowtail (here seen puddling along the New RIver to gain some dissolved salts) from two of its mimics? It can be quite difficult to tell apart from the black tiger swallowtail female and the male spicebush swallowtail. Indeed bird predators must similarly find this problematic and likely avoid eating any of these similarly colored butterflies whether they are palatable or not.

I came across a swarm of viceroy butterflies in Green Valley Park along the S Fork of the New River. This species feeds on toxic willow as a caterpillar and mimics the toxic monarch that feeds on milkweeds. Although these two unpalatable species are quite similar, the viceroy has a dark line across the hindwing that clearly distinguishes it to a discerning eye.

An insect that is extremely obvious at night is the long horned grasshopper or katydid which fills the forest with its calls. However it is rarely seen since it is so well camouflaged. I found a fat female with its posterior scary looking curved ovipositor which is only used to lay eggs at Price Lake. Look how the body closely resembles a leaf even to the venation pattern. Clearly this is a tasty morsel which wants to remain hidden from birds.

One of my favorite insects is the male American rubyspot damselfly, a relative of the dragonflies. This tiny tiger of the streams is a voracious predator both as a nymph and adult. I have only found it in the NC/VA mountains on the edges of the New River at Fries, VA.

A widespread early summer breeding frog that is often confused with the larger bullfrog is the green frog. But note the two lateral folds extending back from each eye which are lacking in the bullfrog. The rubber-band like “boink” of the green frog is also quite different from the “jug-of-rum” call of the bullfrog. The green frog has finished breeding by mid-summer and this male was apparently basking on a cool morning at Brookshire Park.

Some bird migration is underway at this time and we have seen several double crested cormorants at Price Lake. This bird was likely flying from its midwestern inland freshwater breeding habitat to the coast for the upcoming winter. Cormorants swim underwater using their feet and catch fish by pursuing and exhausting them. Their plumage is adapted for this strategy by becoming wet to allow for neutral buoyancy. Thus they have to spread their wings later in the sun to dry out.

As one drives on the Blue Ridge Parkway in late summer you may notice flocks of wild turkeys feeding in the meadows. This flock of 19 birds contained adult males and females and many half grown young.

So while the weather may be sweltering at times, enjoy the natural events that distinguish these “dog star days” of summer.

Bill Dunson

About Bill Dunson

Bill Dunson, born in rural Georgia, skipped 12th grade and went directly to Yale. Bill subsequent-ly received a PhD in Zoology from the University of Michigan, studying softshell turtles. Bill is Professor Emeritus of Pennsylvania State University thanks to a career spent entirely at that institution, teaching and doing research on the physio-logical ecology and ecotoxiciology of reptiles, amphibians and fish. Always curious about nature, Bill has dedicated his life to learning and sharing his knowledge with others. He has served on many advisory boards here in Southwest Florida to preserve the water that gives life to our region.

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