Natural Calendar September 2006

Natural Calendar - September 2006

The purpose of this feature is to give scout leaders, educators and naturalists an idea of some of the natural events coming up each month. We will try to cover a variety of natural events ranging from sky events to calling periods of amphibians, bird and mammal watching tips, prominent wildflowers and anything else that comes to mind. We will also note prominent constellations appearing over the eastern horizon at mid-evening each month for our area for those who would like to learn the constellations. If you have suggestions for other types of natural information you would like to see added to this calendar, let us know!

Note: You can click on the hyperlinks to learn more about some of the featured items. To return to the Calendar, hit the "back" button on your browser, NOT the "back" button on the web page. All charts are available in a "printer friendly" mode, with black stars on a white background. Left clicking on each chart will take you to a printable black and white image.

Notes and Images From August 2006

Marbled Orb Weaver, August 10th, Nikon D70

August is when many of the beautiful orb-weaving spiders can be seen. County fairs taking place at this time of year bring to mind the heroine of E.B. White's classic, Charlotte's Web. Charlotte was a Barn Spider, one of the many species of orb weavers. This Marbled Orb Weaver was catching the early morning sunlight beside the river trail at Barfield Crescent Park in Murfreesboro, Tennessee on August 10th. For more about fall spiders see the feature below.

Sky Events for September 2006:

The Autumnal Equinox, marking the beginning of Autumn in the Northern Hemisphere, occurs at 11:04pm CDT on September 22nd.

Evening Sky: Jupiter is low in the southwestern sky at dusk. At midmonth, look for it about 20 degrees above the southwest horizon thirty minutes after sunset.

Morning Sky: Saturn rises about 3:45am at midmonth. Venus rises at twilight around 5:35am.

All times noted in the Sky Events are for Franklin, Tennessee and are Central Daylight Time. These times should be pretty close anywhere in the mid-state area.

Constellations: The views below show the sky looking east at 9:00pm CDT on September 15th. The first view shows the sky with the constellation outlined and names depicted. Star and planet names are in yellow. Constellation names are in green. The second view shows the same scene without labels. Pegasus appears higher above the eastern horizon this month, as does Andromeda. Look above beta Andromedae and see if you can pick out the faint glow of the Andromeda Galaxy, 2.5 million light years away! City dwellers may need binoculars to pick it out. To get the best view, wait till the square is high overhead to look. If you find the Andromeda Galaxy, you might want to try and see if you can see M33, another nearby galaxy in Triangulum. the Triangle. It will appear in binoculars as a very faint indistinct patch of light. Find the "Square of Pegasus" and work your way outward to the constellations around it.

September 15th, 9:00pm, Looking East

On Learning the Constellations: We advise learning a few constellations each month, and then following them through the seasons. Once you associate a particular constellation coming over the eastern horizon at a certain time of year, you may start thinking about it like an old friend, looking forward to its arrival each season. The stars in the evening scene above, for instance, will always be in the same place relative to the horizon at the same time and date each September. Of course, the planets do move slowly through the constellations, but with practice you will learn to identify them from their appearance. In particular, learn the brightest stars for they will guide you to the fainter stars. Once you can locate the more prominent constellations, you can "branch out" to other constellations around them. It may take you a little while to get a sense of scale, to translate what you see on the computer screen or what you see on the page of a book to what you see in the sky. Look for patterns, like the stars that make up the "Square of Pegasus."

The earth's rotation causes the constellations to appear to move across the sky just as the sun and the moon appear to do. If you go outside earlier than the time shown on the charts, the constellations will be lower to the eastern horizon. If you observe later, they will have climbed higher.

As each season progresses, the earth's motion around the sun causes the constellations to appear a little farther towards the west each night for any given time of night. If you want to see where the constellations in the above figures will be on October 15th at 9:00pm CDT, you can stay up till 11:00pm CDT on September 15th and get a preview. The westward motion of the constellations is equivalent to two hours per month.

A good book to learn the constellations is H. A. Rey's classic, The Stars, A New Way to See Them. Rey's depictions of the constellations and witty commentary are terrific.

A good general reference book on astronomy is the Peterson Field Guide, A Field Guide to the Stars and Planets, by Pasachoff. The book retails for around $14.00.

A good beginners software program for learning the night sky is the Starry Night Beginner program. Visit the Starry Night web site at www.starrynight.com The program retails for around $30.00 and contains a wealth of information.

Amphibians:

Spring Peeper

The frog and toad choruses start waning in September but some frogs and toads are still calling. Another name for the Spring Peeper is the "Autumn Piper", and these small frogs can be heard calling from patches of woods in the fall. Listen also for a very dry, scratchy version of the Southeastern Chorus Frog's song on rainy days and nights in September. On cooler September nights, Southern Leopard Frogs sometimes call and breed as the cooler temperatures mirror their early spring breeding period. We've been hearing the Southern Leopard Frogs at our pond call on cooler August nights. You can locate many of the frogs and toads that have been calling more frequently earlier in the year by driving the back roads slowly on rainy nights.

Marbled Salamander

This is a two person job. One person watches the road for amphibians and one person looks out for other vehicles. Anything over about 15mph is "speeding." On wet nights in September, look for breeding Marbled Salamanders in flooded woodland areas. We found one such area where we had previously heard a breeding chorus of Southeastern Chorus Frogs.

Birds:

Fall migration reaches its peak as September progresses. Be sure to check around ponds, river banks and on exposed mud flats for shorebirds, as many pass through Tennessee in the fall. Hawks peak around the third week in September, and you might want to consider a hawk-watching trip. For good locations, see Bird Finding in Tennessee, below. A trip to the banks of the Mississippi River this time of year can yield numerous shorebirds and large flocks of White Pelicans migrating overhead (we saw 58 birds in one flock in the fall of 2001), and Least Terns flying up and down along the river.

Recommended:

Bird Finding in Tennessee, Michael Lee Bierly. A classic guide to finding birds in Tennessee.

The Sibley Guide to Birds, David Allen Sibley

The Sibley Guide to Birds of Eastern North America, David Allen Sibley

This new Sibley Guide covers only eastern North America, is quite compact, and is less expensive than the larger Sibley.

An inexpensive guide for beginners is the Golden Guide for Birds.

Spiders:

Black-and-Yellow Argiope

Late summer is a great time to observe spiders. One commonly seen spider this time of year is the beautiful Black-and-Yellow Argiope. The body length on the female Argiopes can range up to 1-1/8 inches long. You can sometimes spot the much smaller male Argiope (body length only about 3/8" long) at the edges of the female's web. Black-and-Yellow Argiopes are quite beneficial and feed on a wide variety of flying insects such as aphids, flies, grasshoppers, wasps and bees. Although these spiders may bite when harassed, their venom apparently does not cause problems for humans. Their webs have a characteristic zigzag pattern in the center (see the photo) called the "stabilimenta," so named because it was first thought to provide structural stability for the web.

Argiope Eggcase

One competing hypothesis is that the highly visible threads prevent birds from flying through the webs. After mating, the female Black-and-Yellow Argiope produces one or more papery egg sacs. These sacs (Charlotte's "magnum opus" in the book Charlotte's Web) are round and up to an inch in diameter. Each sac contains from 300 to 1400 eggs. The male dies soon after mating, but the females survive until the first hard frost. The young spiderlings hatch in the fall, but overwinter in the sac and do not emerge until the spring. It's interesting to think about them riding out the winter storms in their protective home.