Native Plants, Habitat Restoration, and Other Science Snippets from Athens, Georgia

Sunday: 31 July 2011

There All the Time  -  @ 03:59:00
These finds are by now almost two weeks old. I found this handsome turtle trudging up the northwest slope early on July 18. I count 16 or 17 scute rings, so while a decade past maturity, he or she is still something of a spring chicken.



This turtle was unusually fearless. I had a good walkaround without disturbing her overly, and it was only when I picked her up to check her plastron that she gave up and withdrew. The carapace pattern, which is unusually bold and rich, is one I've not seen before, and so this is a new find.

This is one of those two or three turtles I've found that has been very hard to sex. The plastron is usually the simplest and clearest determinant for sex. Here is very nearly flat, as it would be for a female, but there is a tiny bit of concavity, though much less than there would be for a clear male. The eyes are a bit reddish, but that is typically an ambiguous determinant. I couldn't get a good shot of the hind claws, which in males would be larger, thicker, and more curved than in females. However the tail just protrudes past the carapace, and is slender, whereas in males it would be thicker and longer, with the tail protruding to the extent that the anus would be visible. So I'm going to count this one tentatively as a female.

Also too, she was headed roughly in the direction of Tom and Gisela's, and we all know that that's the local nursery.

Here are the usual thumbnails - the last one shows the just detectable concavity of the plastron.



Well, that was all within the first fifteen or so minutes of the walk, and I hadn't gone more than twenty yards or so west of the turtle when I found this treasure only slightly buried in the middle of the terrace. The photographs are somewhat foreshortened - the pepsi bottle is actually quite slender.



There's no shortage of examples of this bottle on the internet, but I haven't been able to find much about the meaning of the bottom markings. There's a 13 on the left, in the middle is Ge5, it looks like, with the symbols running vertically, and then a 70 of the right. Normally the 13 might designate a bottle size, the Ge5 might indicate the bottle manufacturer, and the 70 almost certainly is the year of manufacture.

I thought the fine lines that appear on the bottom might even be an embossed feature, but it does look like cracks that have appeared superficially.



Now 1970 is a much more recent vintage than I typically find, but I'm not out for valuing such finds strictly for their age, or discriminating against them for their former abundance. Though only a pepsi bottle, it's certainly old enough and in interesting enough circumstances that it's worth mentioning. It was found along the northwest terraces, nowhere close to the old early mid-century home site. I'd guess it was tossed by a hunter or timber harvester 40 years ago. Who knows what caused it to suddenly make an appearance, but I do walk this area frequently enough to have seen it before.

In 1970 I was 14 years old, just entering 9th grade at South Hall High School outside of Gainesville, Georgia, about 45 miles northwest of where I am now. It was our last full year living there, before we moved to Tallahassee in 1971. It would be 15 years more, 1985, before Glenn and I would be trudging up the hill not 50 yards from where the bottle is now, on our first tour of the property that we'd purchase that year. And of course it's been 25 years since that this pepsi bottle has been hiding from me. For most of that time, so has the turtle!



Tuesday: 19 July 2011

From the Past  -  @ 06:44:36
Occasionally I run across an interesting artifact from the past. Sometimes they are living, like the box turtles, and sometimes relics of a former home site. Both fascinate me, and that's why I document them. On Saturday, it was a colorless bottle mostly buried that I ran across at the top of the Big Gully, about 200 feet northwest of the alleged home site.

The Historic Bottle Website didn't help very much as to the bottle's overall shape. That's not a harsh criticism - the HBW is very useful - it's just that the handle turned out to be vexing, as there are very few photos of handled bottles, and none of this shape. There's a little damage to the neck, but not enough to obscure the screw threads.

After cleaning out the moss and algae and accumulated detritus, the bottle held exactly 1 cup of liquid. It's a little unusual in not having more of a shoulder - rather, the sides slope directly to the neck. It's flattish, but not flat like a liquor bottle would tend to be, and that lack of a shoulder is also something that you'd not see in a liquor bottle. As Glenn said, it's just not masculine enough to be a hip flask sort of thing. Besides, just one cup of liquor? It's hardly enough to get you through the day, especially in the 1930-1940s.

It's a screw top bottle, and so not a decorative cruet sort of thing of the time. And it has a seam that runs up the two sides to the top, so it's machine made, molded, which places it well post-1920s. It has five ribs on each side that proceed from the bottom to the neck, interrupted midway by a square of stippling on each side, presumably meant to help hold a glued label.



The bottle dating page at HBW provided some clues to the markings on the bottom. The "J" in the keystone symbol refers to the Knox Glass Bottle Company in Jackson, MS. This location specialized mostly in milk bottles, and manufactured glass bottles 1932-1952. There is also a "135" and a "2" on the bottom - I would guess the "2" refers to the size and the "135" is a catalog number. I haven't been able to find anything online that would illuminate us further here.



The general shape, along with the handle, suggests that it might have held some sort of sauce - perhaps ketchup or a steak sauce. Glenn has demonstrated its use, holding it loosely by the handle (please be careful) and then tipping it with his other hand on the bottom. Or it could have been a non-food liquid. Surely something mundane, but that's not a disappointment in a find that is probably 60-70 years old, and represents the last previous occupation of our home property.

Most of the finds over the last few years have indicated a date of that occupation sometime during the 1930s to the 1950s. There was the Temple Garden bottle that suggested an earlier date ca 1920s. And I found a more precise date of 1943 on the moraline jar, last year.

It's not completely out of the question that one or two of the box turtles might have directly witnessed all this.


Sunday: 17 July 2011

How Many Are There?  -  @ 08:28:11
We've had a pleasant change in the weather since Thursday night, when we returned from sweltering training to cool breezes and impending storms. On Friday, the temperatures dropped and the high was in the upper 70s, something that has not happened since May 18. Yesterday Saturday was a little warmer, and today might reach upper 80s. Then it's back to above normal with 100F temperatures predicted for Wednesday and Thursday.

I've been getting all the box turtles in a row, or rather, multiple rows on excel, and dabbling a bit with mark and recapture analysis of the findings over the last six years. The goal is to estimate the size of the box turtle population on the property, although I'm violating somewhat some of the mark and recapture methods.

Mark and Recapture:

Mark and recapture experiments are fun to perform - biology student labs often attempt this with butterflies in the field or fish in a tank. The idea is to make two "visits" to a defined area. Each visit, as many animals of the species of interest are captured as possible. On the first visit, the individuals are captured, marked in some way, and released. The total count is M. On the second visit, a similar intensive capture is made. The total count is C, and of these some number R will have the markings of the first visit's capture.

One simple model, the Lincoln-Petersen model, assumes that the proportion of marked individuals recovered among the total counted in the second visit is the same as that of all the marked individuals relative to the total population N.

So R/C = M/N , and N = M*C/R .

The mark and recapture experiments rely on some assumptions:

1. Marking does not perturb the animals, and markings are not lost. (In my case, "marking" is photography of the carapace patterns for matching).

2. Related to 1, marked individuals should not become easier or more difficult to recapture. Similarly animals in the second visit should not become harder or easier to capture, compared to the first visit. (Unless our turtles sound off "Oh god, hide. Here comes the creeper with the camera again," we have no worries.)

3. There is no emigration or immigration of animals into or out of the study area during the study time. (In my case, there probably was movement into and out of the area, although box turtles tend to be territorial. Still, we know some of the turtles observed here during the "first visit" have been spending time over at the neighbors', and so it's likely that some movement is violating this rule. Some box turtles take up a wandering lifestyle, staying in one place only a short time before moving on.)

4. Related to 3, the time between visits should be short enough so that movement of individuals into or out of the study area is minimized, and mortality does not occur. The time between visits should be long enough for individuals marked and released from the first visit to become interspersed with those not captured. (For box turtles, this time can be extended because of the territoriality and the low mortality rate of adults.)

There are other assumptions, but most are common sense.

Study Area:

Although I've done turtle observations over most of our property, bounded in red below, I've confined the counts made here to the area I've most intensively covered, the 20 acre (8 hectare) area marked in green.

You can ignore the blue dots and other unexplained markings - this is a map left over from some other purpose a couple of years ago.


Our property as a whole is relatively isolated. Goulding Creek bounds it on the north, and across from Goulding is more habitat of the same undisturbed sort. Black Snake Road uphill in that direction is a dirt and gravel road not presenting much in the way of traffic concerns. Goulding Creek and its attendent floodplain and hardwood forest is a major wildlife corridor into the study area. SBS Creek runs through the study area along a hollow from south to north, and is generally active year round, running dry during the summer for only two consecutive years since 1985. The forest upstream and downstream is hardwood - mostly white and northern red oaks, hickories, and beech, with hornbeams, buckeye, dogwood, and some redbud in the understory. Mayapples, woodvamp, muscadine, and poison ivy are common understory ephermerals or vines.

On the northeast side of the study area is an uphill slope, and this too represents a known box turtle corridor. To the east and southeast is mostly upland pine forest with some recent hardwood coming back, and this is true for much of the land to the west - not great box turtle habitat, but permeated by lowland hardwood forest. Its 300 acres represents a buffer disturbed on decade intervals by some logging. Wolfskin Road running along the south from west to east obviously represents a significant problem in traffic related mortality, and there is on either side coverage by human development - residences and/or pastures.

Predation and competition: predators of adults are probably mostly coyotes, perhaps the occasional raccoon or fox, although it's been years since I've seen a fox on the property. Raccoons, opossums, canines, larger birds, and probably snakes can manage baby box turtles easily. The recent incursion of armadillos into the area may offer direct competition for resources.

SBS Turtle History:

I did not plan on doing a mark and capture - this analysis just came about after looking at all the data I had and wondering if I could find a way to rationalize using it to estimate a total population size. So I've abused the model somewhat, mainly by dividing a five year study period into two periods of 2 years (the first visit and "marking" period) and 3 years (the second visit and "recapture" period).

These are rather lengthy sampling periods, but for box turtles they may not be too long to yield results of some value. Probably the worst effect is that of turtles wandering into or leaving the area. This reduces R, the number rediscovered in the second visit, and therefore inflates the total population estimate. So our result is more likely to be an overestimate.

Our first "visit" covered Nov 2005-May 2008. During this time I came across and photographed 11 unique turtles (M) within the study area.

Our second "visit" began where the first one left off, May 2008, and is ongoing. During the past three years of the second visit, we've found 14 total turtles (C) and 4 of these are "marked" from the first visit (R).

Results:

Our estimate of the population size in the study area is therefore 11*14/4 = 38, of which we've seen 21. That's somewhere around 4.8 turtles per hectare, or 1.9 turtles per acre. This is not an unusual population density in a forest location.

A few other results:

Over the last 5 years, I've found 3 dead adult turtles. That may be a rather high mortality rate for a population of 38 turtles: 7-10% over 5 years is 1.4-2% per year. In these three cases the cause of death was most likely disease, or weather related.

Of the 21 unique turtles observed, 10 were male and 11 were female.

Not included in the study were the turtles found in the 20 acres west of the study area. I've found 9 turtles (6 male and 3 female), but this area has only been observed for a couple of years, and not nearly so intensively.

Also not included were last and this year's observations by our neighbors. They have found 5 previously unobserved turtles, and an additional 3 that had been previously marked by me. One of these was not included in my estimates, since I never actually came across Maggie a second time. Of the 8 unique turtles they've photographed, only one (a rediscovery, Ernest) was definitely male. Most of the females were in the process of digging nests.

The total number of unique (live) turtles found: 35, with 6 of these found at least twice.

I ran across an interesting PhD dissertation (pdf) by Nathan Nazdrowicz, surveying box turtles at four study sites in Delaware. He and his colleagues were, of course, far more meticulous, intensive, and consistent in their observations, and use more complex models to tease out a great deal more information on their populations.

I particularly liked the descriptions of the study areas - a little history of the area itself, the forest community, its degree of isolation and connections by wildlife corridors, and the encroachments by development around them. To give you an idea of the difference in scale, "From 16 April 2001 through 14 November 2002, we captured 268 turtles 892 times on the 4 study sites. We captured 16 turtles 77 times at the University of Delaware Woodlot..."


Besides the occasional documentation of discovered individuals, here are some links to relevant previous posts:

First turtle blog entry 11 Nov 2005
The comments that probably got me started on this: 28 Jul 2006.
Reflections on box turtles as property owners: 9 Sep 2008.
Yellow box turtle: 21 May 2008.
The turtles of 2009: 2009.

And of course, the babies:

Views of the babies: 18 Sep 2009.
Characterizing the babies: 19 Sep 2009.
Releasing the babies: 23 Sep 2009.


Monday: 11 July 2011

Two Note Song  -  @ 09:09:02

First note: Let's take a quick look at what normal and abnormal Julys look like.

We don't have a huge amount of variation in rainfall from month to month - we have no dry or wet season, not really. In July, we expect 4.8" on average. This has ranged from over 10" in 1964 and 2001 (NOT due to tropical storm activity) to a low rainfall of 0.99" in 1947. That latter is interesting because it's not a particularly small amount of precipitation - not like some months. So far, by July 11, we've had just under an inch - lower than usual, but not unusually so.

Rainfall predictions are difficult because rain can fall at any time, or no time, and we don't have any preconceptions. Temperatures are different: July is expected to be hot, hotter by a hair than August, for instance. But we've already had more than all the 90+ temperatures, to date 59 such, that are normal for a summer, on average 37 +/- 16 such days.

Here are the historical statistics for temperatures in July, since 1949:



As is usual, I've counted the number of days for each category in the "high" and "low" columns, and these summary statistics appear in Rows 1.

Rows 2 show a particular hot July, the hottest with 7 July days over 100F, and the rest above 90F, in 1993. This was our third summer in Wolfskin, in 1993, and yet I cannot recall this as a hot July. In 1993, email was just really getting going for a lot of folks, and the "world wide web" had barely begun to accumulate actual web pages to its credit. There just wasn't those easy sources of information that made it possible to gather and analyze those data.

July 1967 was particularly cold, with no days above 90F. You might recall that the 1960s were particularly cold, a likely result of hydrocarbons and aerosols in the atmosphere that reflected and blocked heat input from the sun. The Clean Air and Water Acts helped to diminish that effect rapidly in the 1970s, and we haven't had such a cold summer since.

Row 3 shows the 11-day current result, plus five days of prediction. We *might* have a couple of days below 90F later in the week, and Tuesday might go over 100F, otherwise it's the ongoing inexorable 90F+ daily highs that we've seen with just a few exceptions since the first of May. I don't think we'll come close to July 1993, but we can't be sure of that - there are at least two weeks remaining beyond what we think we can foresee.

Second note: Our neighbor Gisela sent me a photo of a nesting box turtle on July 3, observed as so many have in the past year along their drive, nesting.



I had a little trouble locating her, but she is definitely the one I documented in May 2007. At that time she was in the Kat Sematary, 300 feet south of the house, and so she had to travel 1000-1200 feet straight line NNE to get to this nesting site last week. She holds the record, so far, of the longest period of time between observations.

She has an unusual row of yellow spots across the front scutes, and then another row just behind that. She also has sustained some damage to the top of her carapace in the last four years.


Tom and Gisela have observed a large number of females nesting along their drive, this season and last. Of the six, I believe, I have been able to recognize at least three now that I've seen before, generally 1000 feet south and firmly within our property. It really appears that they have some kind of interesting nursery magnet that draws females from quite some distance, for a box turtle.


Tuesday: 5 July 2011

Sipping Sweat  -  @ 06:50:51
Since it's hot and the humidity has gone up somewhat, sweat now accumulates rather than drying, and so we have sweat bees. Notice the tongue - in all the photographs I took, it always targetted behind and under the rest of the body, never forward of it. I'm not sure what that means. For a tiny bee only 3 millimeters long, at the edge of camera competence, the tongue is quite a large and heavy organ!



Sweat bees are in the family Halictidae, which is divided roughly into the green ones and the not-green ones. They're probably much more interested in bountiful flowers and their nectar and pollen, but people sweat seems to draw some of them, and they are persistant once they've found you.

Most people will be annoyed by sweat bees - I have no trouble with them and despite the long photo session, this one navigated me for close to half an hour. Yes, they tickle, true, but if there is one nearly ironclad rule it is that feeding bees are happy bees - unless you physically assault one while it's feeding, you aren't likely to get stung.

Still, if you're allergic to bee venom, anecdotal evidence from google hits is that these are problematic too. I have been stung on occasion when I absently rub the tickle without thinking - it's a very tiny sting - nothing at all like a honeybee, for instance.

Bugguide tells us that "some" species of the Halictidae go after sweat as a water source. That should make this one easier to identify, but they don't say *which* species. If this specimen were one of the green halictids it might be much easier but as it is not I've just kind of given up. Still, I'll include some thumbnails to larger photos if anyone wants to take a shot at it. I note the very faint banding on the abdomen, and absence of obvious coloration beyond drab.





Saturday: 2 July 2011

The Month of June  -  @ 06:38:22
It's The Month of June, Number 65 in a series. June was very warm for us most of the month, the most of any June in the last 60 years, as we will see. Others saw other extremes.

Here are the usual temperature anomalies products, at the National Weather Service Climate Prediction Center. The mean anomalies can be had on a new page by clicking on the image below.


The West and northern midwest continued cooler than usual - the west for the third month in a row, and the northern midwest since February. The south and Atlantic states were warmer than usual, continuing a trend since the beginning of the year.

The south had much warmer high temperatures, but nighttime lows were also warmer than normal for much of the eastern half of the country.


We find the National Weather Service Climate Prediction Center's precipitation plots here.

Much of the northern half of the country received normal or surplus rainfall, to their continued misery, but the drought continued across the southern states from AZ to FL. Southern states along about our latitude and east of MS had some relief in the form of impressive thunderstorms during the third week in June. The drought west of the Mississippi deepened, and overlapped both warmer and cooler than normal regions.




For Athens:

Here is a plot of our temperature swings in June, along with precipitation amounts as experienced in Wolfskin:



We've already discussed the unusual number of days in May that received 90+ high temperatures. That trend continued in June, with a record 28 days receiving 90+ high temperatures. This was a remarkably even temperature pattern, persisting all month long, although the absolute highs never broke a record.

Here is my plot of high temperatures for the month of June in Athens. As usual, the black dots are for the years 1990-2009 (black dots), 2011 (green line), and 2010 (red line).



Our high temperatures were much higher above June's average 87.2, by 6.8 degF. This isn't record breaking, but our 94 degF average high is the fourth highest since 1920. Only 1925, 1931, and 1933 were higher. We didn't break any high temperature records in June.

In June, there were a remarkable 17 days more than one standard deviation above the norm (4.8 days normal). We had only 1 night more than one standard deviation below normal (5.1 nights is normal). So even our nighttime lows averaged higher than normal, but by only 2.6 degF.

In the end, with 28 such days, we had the highest number of days 90F and above since 1948, and coupled with the 13 such days in May, an unprecedented run of consistently hot weather.

The figure below shows the Athens precipitation data which are official for our area. As usual the green line shows our actual rainfall, the red shows the average accumulation expected. The black dots are rainfall over the last 20 years, the vast river of peach shows the standard deviation.

June continued dry until we began to get some rain in the form of impressive thunderstorms around mid-month. The plot below, of Athens data, shows a lower total than we got in Wolfskin. We had 4.84", but the rainfalls were very heterogeneous in the second half of the month. The 2.44" total rain for Athens is not supported by most of the higher totals by CoCoRaHS observers.



The neat prognosticator largely failed in its predictions for April and May, and were so-so for June. High temperatures never went down, and the only reason they're looking about normal now is because the end of June and into July and August is *supposed* to be hot.

For what it's worth they seem to have figured things out - hotter than normal for us in northeast Georgia for the next three months. Precipitation variable, but chances are closer to normal than abnormally dry (or wet). A tropical storm could make a big difference at anytime, of course!

ENSO stuff:

The ENSO PDF update at this page still chokes on download - wish the Climate Prediction Center at NWS would get that fixed! The power point option is ok, though.

La Niña ended in February, after a nearly year-long manifestation, and normal ENSO conditions are in effect, just in time for hurricane season! ENSO neutral conditions are expected through our northern hemisphere summer.

NOAA's Monthly State of the Climate product for May is now up, and addresses the record rainfalls and flooding in the midwest. It confirms that the southeast was anomalous in its dryness, compared to the rest of the country - Georgia, which also broke records for highest temperatures ever recorded during May (Waycross @ 104F), had its fifth driest May on record.

June should be appearing soon. Detailed explanations for weather events occurring during whatever month is current can be found for the several sections of the US under the National Overview. There are many interesting weather- and climate-related items to be found here.



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