A End of Summer Nature Ramble

September 15, 2014

Nature Notes by Bill Dunson

Although frost was delayed last fall until Oct. 20 at our VA farm, I am not counting on such luck this year, and am enjoying every day left of the bounty of summer. Of course fall brings its own natural pleasures in fruit production, migration of birds, and appearance of some insects and flowers characteristic of late summer.

One of the more interesting traits of fruits is the variation in color. Winterberry, a holly that grows in damp soil, illustrates the bright red type which must especially appeal to birds with color vision and few taste buds. Holly fruits are low in sugar and rather tasteless, and seem designed to be eaten over a long period of cold weather. A striking contrast occurs with black gum tree fruits which are dark in color and tasty if somewhat pungent. Birds such as thrushes avidly seek out black gum fruits during migration and may find them with the help of numerous reddish leaves which appear on the tree. This is an example of “fruit flagging” whereby a plant advertises its drab fruits to birds with bright leaf color.

A sure sign of the end of summer is the migratory departure of the large green and blue common darner dragonfly, and the appearance of the equally large shadow darner, which can persist even after some frost. This seems a type of “changing of the guard” by two species that may occupy almost the same niche but share it temporally. I also find the great spreadwing damselfly mostly in later summer and early fall around fish-less ponds. This species has been enlarging its range in recent years from the SW to the eastern US.

In our wildflower meadows flowers are diminishing quickly and there are fewer butterflies, but I did find an interesting predator, the white banded crab spider. This ambush predator lurks on flowers and grabs unwary insects that come for nectar or pollen. This particular spider actually chose a flower, the purple coneflower, that was inappropriate for its whitish color and it was thus very obvious.

As the air temperature gets cooler you may sometimes find reptiles basking to raise their body temperature. This snapping turtle was hauled out on a rock in one of our ponds and seemed to be very content acting like a sun bather. Snappers are not as often seen basking as typical pond turtles, but they obviously benefit from raising their temperature above that of the surrounding cooler water on sunny days.

One of our resident and cryptically colored birds is the song sparrow, a very common bird in our fields and thickets. It will remain here all year but be joined by migrant white crowned sparrows from Canada as winter residents. We are also enjoying the last of the migrating ruby-throated hummingbirds which are feeding on both native (jewelweeds especially) and yard flowers (including red hot pokers originally from S Africa). I got a close view of a young male with speckled green feathers on its throat and a blob of pollen on its upper bill. These hummingbirds are bulking up on nectar in preparation for their marathon flight across the Gulf of Mexico.

So even at the end of summer there is much of interest for the naturalist to enjoy.

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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