NATCHEZ NATURALIST
NEWSLETTER:
from the woods near Natchez, Mississippi, USA

August 18, 2002

OCEAN BREEZE FRONTS
Though this week has been relatively cool for August (not over 90° here -- 32°C), it's been profoundly humid. Constantly fog condenses inside my glasses and on my computer screen.

Such humidity means that afternoon rains are very likely. In fact, it's rained at least a little here every day this week. This is glorious weather for mosquitoes and mushrooms. Though few edible mushrooms are up, there's a world of those tiny ones with slender stems, of the genus MARASMIUS. You can see one of the most common Marasmius species, one growing on pine needles -- MARASMIUS ANDROSACEUS -- at www.mycena.sfsu.edu/hawaiian/Pine_Forests/66.JPG

Early in the week we saw classic examples of a certain weather pattern very typical for here during the summer. Around dawn the weather map on the Internet shows nothing happening in the region, except that just off the Gulf Coast south of here small storms are developing. By around 9 AM these storms have grown and moved inland. By noon the storms form a distinct frontal line extending well inland, exactly like a frothy wave at the beach rushing ashore. Behind this north-moving wave's front, each hour the storms increase in size and number. Typically by noon the advancing wave-front lies around Baton Rouge, and often by this time I am already hearing thunder. By 3 or 4 PM majestic thunderheads tower all around and the thundering is general. The clouds and associated wind cool things off nicely. About half the time there's at least a sprinkle, and maybe a fifth of the time we get a shower, seldom over half an inch (12 mm).

A friend has told me that this inland-advancing weather is referred to as an "ocean breeze front." Years ago in meteorology class I learned how during summer days land along any coast heats up faster than the ocean, and as that hot air above the land rises, cooler air from the ocean is sucked inland to take the rising hot air's place. On a regional basis this mingling of cool and hot air causes instability, and therefore storms. It's taken until now for me to understand that ocean breeze fronts can reach inland as far as Natchez. We are about 150 air-miles (240 kms) north of the Gulf Coast.

I enjoy visiting a certain Internet site where animated weather maps are presented showing the last few hours of the current day's storm activity in our area. If you'd like to see an ocean breeze front on that map, wait until 3 or 4 PM Natchez time, when the front should be well developed, and then click HERE

If you don't see what I'm referring to, then wait a couple of days and try again, for sometimes the front doesn't develop -- as has been the case during the latter part of this week when upper-level winds from the southwest overwhelmed our elegant ocean- breeze-front phenomenon.

*****

LOUISIANA WATERTHRUSH
For the last few days I've been hearing a new "chek" sound here and there among the trees, a sound not heard since spring migration. Lots of birds make chek sounds so it wasn't until I spotted the visitor that I realized it was the Louisiana Waterthrush, SEIURUS MOTACILLA. We're right on the southern edge of this species' summer distribution (winters in the West Indies, Mexico and northern South America) so he's not an early fall migrant. I think he's just finished nesting elsewhere in the area and in a birdy way now is "hanging loose" and wandering around exploring new territory, getting into the mood to wing southward. You can see a map of the Louisiana Waterthrush's summer distribution at www.mbr-pwrc.usgs.gov/bbs/htm96/map617/ra6760.html and a nice picture of the bird itself at www.ronausting.com/LaWaterthrush52.jpg

If you ever spot one of these birds in nature you'll never forget it. That's because of how it moves around its rear end. It's so comical looking that the first time you see it you're bound to laugh. This bird's tail is very short so it's not tail-wagging we're talking about, but rather the bird hefting itself up on longish legs and moving around its entire rear end in an exaggerated bobbing and teetering motion. You can't visualize this, you just have to see it.

In North America there's another similar looking, tail-bobbing waterthrush, the Northern Waterthrush, who migrates through here but that one spends its summer far north of here. So, the question is, "What's behind this rear-end movement?"

Both waterthrush species nest along streams and in cool ravines. Though they are considered to be warblers, and warblers are thought to be tree dwellers, waterthrushes dwell on the ground. Interestingly, in Europe in very similar habitats there are kinds of birds known as wagtails who, despite being completely unrelated to our waterthrushes, bob around their rear ends just like our birds. Why would two completely unrelated kinds of bird occupying the same habitat on different continents develop identical behaviors?

I'm not sure how to answer that. Often when a creature draws attention to its tail it's to keep predators from attacking its head. But that doesn't incorporate the fact that waterthrushes and wagtails occupy similar habitats. Whatever the case, this must be a wonderful example of "convergent evolution" -- a case where the same adaptive "idea" occurs in completely unrelated species so that over time the looks and/or behaviors of the two species come to be the same.

*****

VELVET ANTS
Often as I work at the computer I glance out my screen door and there's a Velvet Ant, sometimes known as Cow Killer (DASYMUTILLA OCCIDENTALIS), rushing around on the bare ground between my door and the outside kitchen. These fuzzy, boldly patterned, red and black creatures are about 3/4 of an inch long (2 cm) and even if you don't know that they can sting, something about them just says "stay away!" You can see one at www.forestpests.org/publichealth/small/0001025.jpg

Velvet Ants are actually wingless wasps, and that's why they sting so well. Nowadays they are rushing around on the ground looking for burrows and tunnels of ground-dwelling wasp and bee species, which Velvet Ants parasitize. The female Velvet Ant deposits her egg(s) in underground nests of these species and then the developing Velvet Ant brood feeds upon the larvae of the wasp or bee, or the stockpile of food left for the developing wasp or bee larvae.

Despite Velvet Ants looking so soft and fuzzy, they actually have very hard husks, or exoskeletons. This protects them from stings of the wasps or bees they parasitize.

*****

SULPHUR BUTTERFLIES
Last Sunday afternoon I visited the "Miller Field," a field of maybe 15 hilly acres (6 ha), now grown up in weeds and a favorite place for Wild Turkey. I saw about ten turkeys along the edges, and lots of places where they'd scratched and taken dust baths.

At the top of one hill the full strength of the afternoon sun beat upon me, but it wasn't bad, since a brisk breeze was blowing, making nice waves in the tall grass and weeds. White and gray thunderheads towered all around giving the sky a dramatic look. It was a splendid moment, reminding me - except for the heat -- of sunny, windy days in alpine meadows.

Several Sulphur Butterflies flitted around me. Sulphurs are medium-size, yellowish butterflies, the yellow kind that gave butterflies their buttery name, and they tend to fly fast, to dart about, and not stay long in one place.

I think there were two species there, the Common Sulphur, COLIAS PHILODICE, and the very closely related Orange Sulphur, COLIAS EURYTHEME. Before agriculture came to North America the Common was basically a northern and eastern species while the Orange was based in the West and South. When North America's biomes fractured into fields, which both species love, each species spread into the other's range.

The literatures says that when both species are superabundant in alfalfa fields they often hybridize, producing in-between-looking offspring. However, at lower densities the two species "breed true," so the two species do not appear to be merging. This is about as close as two distinct species can be and still be considered separate species. Apparently the two species evolved from their common ancestor relatively recently in evolutionary history.

You can see a picture of the Common Sulphur at www.princetonol.com/groups/mg/cloudedsulphur.jpg and one of the very similar Orange Sulphur at www.duke.edu/~cwcook/pix/osulphur01s.jpg

*****

ANTS ON BLACK-EYED PEA VINES
Many plants, especially in the tropics, possess glands producing ant-attracting substances. Ants protect these plants from browsing mammals who don't want to eat a plant covered with biting ants.

The Black-eyed Pea vines in my gardens are making my garden ants very happy right now, for every Black-eyed Pea fruiting head is well equipped with glands, and ants feeding at those glands.

In order to scan these glands for one of my web pages I broke off a piece of the vine, shook the ants off, and brought it home. I placed the gland-bearing sprig on my table and forgot about it for a few minutes. Well, you have heard about the lines of ants always marching in my trailer. By the time I had my scanner ready, the sprig was crawling with ants. When I placed the sprig on my scanner the ants were so absorbed in their meal that most of them didn't even move. You can see the scanned results at www.backyardnature.net/spines.htm#a

*****

A DISHPAN CROWDED WITH TADPOLES
In the two previous Newsletters I told you how on July 31 frog eggs were laid in my dishpan. Since then, each day activity there has increased, and now things are getting crowded.

The day they were laid I realized that the dishpan could never support so many tadpoles if all the eggs should hatch, so I dumped what I thought was all the eggs into a small, water-filled, metal tray salvaged from the bottom of a junked refrigerator. The tray is kept on the ground next to the trailer to supply water for birds, butterflies, raccoons and the like. Obviously I didn't succeed in dumping all of the eggs for today about 200 tadpoles wiggle in my dishpan. Interestingly, in the ground tray where I must have deposited several thousand eggs, there are only two or three tadpoles. Something has controlled tadpole population there, but not in my dishpan.

My dishpan has a bit of algae in it (their main food) and occasionally I thump a crumb of cornbread into it, which the tadpoles seem to relish. However, each day as the tadpoles grow the algae diminishes markedly and I am less disposed to sustain 200 incipient frogs by feeding them cornbread -- especially since my meal is running low and I dread the trip to town.

There seems to be a morality play in the making here. I'm not sure how it will resolve itself. I'll let you know.

*****

IF THERE WERE AN EINSTEIN TADPOLE
My dishpan drama is developing during a week when I am reading essays by Albert Einstein.

In his essay "Religion and Science," Einstein considers man's religions from an evolutionary perspective. He notes that primitive religions concern themselves with gods who manifest themselves in more or less understandable forms (as plants, animals, rocks, symbols, humans), and their main job is to grant favors and protection. A later-emerging type of religion conceived of there being a single "God of Providence" ("providing god") rather like a celestially based, stern but loving patriarch in a large family. Our current major religions, including Christianity, are of this kind. Finally, there's what Einstein calls the "cosmic religious feeling," which conceives of a universality (which I would think of "the Creator") to which it is pointless to pray for favors, but which is so majestic and awe-inspiring that by reflecting upon it one is "filled with the highest kind of religious feeling," as Einstein writes.

If my dishpan tadpoles were somehow to begin feeling a need for religion, I wonder what gods they would come up with? I suppose that some might begin worshiping certain algae cells some one of them had espied glowing a certain way suspended in the water in a beam of sunlight, or maybe they would worship their own reflections in the dishpan's shiny aluminum. The more sophisticated tadpoles might sometimes catch a glimpse of me with my magnification glass looking down at them -- this huge eye-in-the-sky, the God of Providence who thumps them cornbread -- and they would produce tadpole priests and tadpole mullahs and tadpole rabbis who would assiduously and interminably interpret and reinterpret the meanings of every little thing I did.

And if there were an Einstein among them, I suppose he would just keep quiet and write in obscure forums, suggesting that it is hardly to be expected that the God of the Cosmos would be at the beck and call of every wiggly little tadpole in a dishpan... though in truth it is quite wonderful for this brief moment in eternity to be granted the perspective of a tadpole in sparkling water temporarily pooled on a random, laughing hermit's warped and moldy, falling-apart, outside table.