I am still enjoying the diversity of life at the very end of the fall growing season for flowers and insects. Soon for many species there will only be memories that will have to last us until next spring. But there are some intriguing signs of the season that involve replacement of some species by others. If you did not know what month it was, it would be possible to make a pretty good prediction by observing some of the following species.
The unusual stiff gentian is a characteristic fall species with a flower that does not open fully. It has been called “ague-weed” due to the fact that a tincture of the root was used in the past as a bitter tonic to treat headache, jaundice, constipation and a weak appetite. I enjoy finding it as a sure sign that we are in early fall.
In the fall you may often notice caterpillars wandering around looking for spots to over-winter as pupae or sometimes as a caterpillar. The huge bright green caterpillar of the beautiful polyphemus moth seems to be well designed to escape the notice of bird predators by blending in with the surrounding vegetation. A brown form of the very different Pandorus sphinx moth caterpillar is similar in that it can blend in with brown vegetation, but it also has a remarkable eye spot on its hind end. This could have at least two functions- to dissuade birds from attacking it by appearing to be a scary snake, or alternatively leading a predator to attack its posterior end which would be less vulnerable than the head.
Another sure predictor of the fall season is the migration of common green darner dragonflies to the south, and their replacement at our ponds by a similarly large but quite different shadow darner. Such a temporal displacement of one species by another is a means of sharing the same niche by two species at different times, leading to an increase in biodiversity and avoidance of direct competition. The aquatic larvae are likely living in the same ponds simultaneously, but may minimize competition for food since they mature at different times of the year.
While ruby-throated hummingbirds leave northern latitudes in the fall, they may continue to use the flowers that remain and feeders that are left out as they migrate south. We grow a specific hummingbird flower, the pineapple sage, which is tolerant of cold but not freezing temperatures, and very attractive to hummingbirds. Indeed this photo shows one of our hummers feeding on this sage in our backyard. One of the photos shows the back of the hummingbird, an iridescent green color, which blends with the vegetation and would be well suited to helping them escape from predation while they are perched and torpid at night or during cool periods. This sage flower is also used to attract western hummers such as the rufous which sometimes migrate to our area.
One of the most impressive and distinctive fall migrations of birds to the south are the movements of the wood warblers to Central and South America. This beautiful male Cape May warbler spent some time at our gate catching gnats in the early evening of Sept. 23. Now in early October we are getting considerable numbers of palm warblers moving though as they head to Florida for the winter.
So do not despair as the fall season and Jack Frost bring an end to the marvelous panoply of life that we have enjoyed during the warm seasons. There is much of interest to the naturalist during fall that will engage our minds and hearts to better understand how life adapts to the changing seasons.
Bill Dunson, Englewood, FL & Galax, VA