Ok, this is something I can’t explain – I’m hoping someone else can help.
The slideshow below consists of a series of images taken about an hour apart last June by one of the timelapse cameras at The Nature Conservancy’s Niobrara Valley Preserve. Hover your mouse over the images and you can click the arrows to move between photos. Watch the stick in the foreground…
What in the world? The stick doesn’t do it most days, but on some days, the timelapse camera captures one end of the stick rising into the air. Overnight, it returns to its previous position.
Here it is again, a couple weeks later:
Later in the season, the stick was dislodged so one end was no longer in the ground. It still moved, but in more of a twisting motion. I think the stick just to its left is moving slightly as well?
This is not a living entity. It’s a stick; dead and disconnected, but still able to move.
My best guess at an explanation is that the stick is moving because of moisture. Over time, the stick absorbs moisture and then dries out, and the shrinking and swelling of the wood could change its shape. Because humidity tends to rise overnight and fall during the day, that could explain the pattern.  But, if daily humidity patterns are affecting the stick, why doesn’t it happen more often?  Also, in the October series above, the stick was lifting as it rained, so that seems counter to my hypothesis…?
Anyone else have an explanation? I love a good mystery…
The Prairie Ecologist 
How deep does the right-hand side of the stick go into the sand/mud? Maybe it still has some roots (or not) and is absorbing water?
Right, I thought about that too, but looking at the third series of photos when the stick is completely on top of the ground, it’s still moving…
I think you are on the right track WRT moisture. I would guess it is drying and moistening and this is causing distortions in its shape.
I am guessing your explanation about the stick absorbing moisture then drying is correct. It does bring a whole new meaning to the old phrase of “Being a stick in the mud”!
Are you sure the elbow that is touching the sand doesn’t get pushed up and down by sand flows and changes? It looks to me like the sand moves down the creek and builds up under the stick, then it is washed or just shifted away again.
Kim, there is sand deposited after rain events a few times during the 2013 season, but the sand doesn’t appear to be moving during the days the stick moves. At least not enough to move the stick (as far as I can tell). The photos are from the bottom of a draw where sediment is deposited after it washes down from above. I think your hypothesis would be good if the stick were moving between days (as rain events brought more sand) but I don’t think the sand moves on an hourly basis. Crazy isn’t it?
I also agree with the moisture content changing. I do woodworking for a hobby and one thing is you put finish on both sides of a table top so moisture changes are the same. If you finish the top of the table and not the bottom, then the top will cup with humidity changes. Your stick’s moisture content becomes less on the top causing it to move in the air during the day. When the sun goes down and the temperature becomes closer to the dew point it takes that moisture back in.
I wonder if it is a combination of both humidity and barometric pressure?
Karen – a couple other people have responded privately to me suggesting barometric pressure. I don’t understand WHY barometric pressure would make sticks move, but apparently it has that reputation… http://www.theweatherstick.com/weather-stick-history.html
I think the movement has to do with the asymmetric growth of trees. If you look at tree rings, the rings on one side of any given tree will be wider. This is also true of the smaller branches. If I remember correctly the underside of branches typically have thicker growth rings allowing them to support weight better. The difference in thickness and density of the tops and bottoms of branches would cause them to bend with changes in temperature, barometric pressure, and moisture content. Although, it appears barometric pressure changes must be the most significant factor given your observations.
Temperature could also be a factor. I definitely think an experiment in a controlled laboratory environment is in order.
Chris
I just received a catalog with this same weather stick in it!!! Only $6.95 each!!!!:^)
Perhaps you should investigate what kind of sick it is. The surrounding trees appear to be broadleaf.
Chris,
If this had been reported yesterday, I would have asserted that it was the work of an invisible gnome or leprechaun. It is probably a fun little teeter totter if you are a little ‘un.
Erin go bragh!
Obviously this phenomenon is related to the suddenly appearing cow path. These are not natural. They are tricks played on you by Aliens. They’re messing with your head.
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Chris,
My architect hat on now. Some wood can change 10% in dimension across the grain and 1% with the grain. It twists due to differential moisture and cell heterogeneity. What fascinates me is that it appears to be rapidly reversible in the specimen.
Hi Chris,
I don’t see any slideshows but if it’s raining, that would raise the water content in the ground/ level of the ground right? So assuming you mean the stick is stuck in the ground, it would rise slightly. Just guessing since I can’t see what you mean. Also what about the freezing/thawing cycles for the non-rain question?
Suzanne
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Are you SURE it’s just a stick and not part of a tree root?
Definitely not part of a tree root – or at least it’s definitely disconnected in the third series (October) and is still moving then.
I am reminded of certain seed pods such as those on redbuds that split and then flex or twist open to release the seeds, an action that I believe is caused by changes in moisture content. Problem is, I don’t think any of those “unflex” if they get rained on. Probably aliens.
Hi! Over here in Finland people have used weather stick as a barometer for I don’t know how long. It is made from domestic spruce, maybe a 3 feet long piece of stem maybe 3 inches thick and with a branch, stem split and peeled, and nailed (stem)upside down to a wall and the the branch will go up and down with barometric changes.
How interesting, Risto! I love the curiosity in this post! One of the many reasons I love this blog.
My first instinct tells me this is a root from one of the trees on the edge of the wash and is drawing moisture from the air. The moisture causes the root to move about. It is hard to tell from the images if it is a root or just a stick in the ground but if it is a stick why hasn’t it washed away.
I agree with the moisture comments. Also, interesting to note the changes in hardwood stump sprouts and bark sloughing on the larger fire-killed trees.
Definitely moisture changes! Not sure why it doesn’t happen every day, but here’s my thoughts:
1. Put a flat board on the ground. 2 days later it’s not flat anymore. There’s a moisture gradient from bottom to top of the board, causing one side to expand, causing massive bowing. I’ve seen the amount of bowing change in a 2×4 over the course of a couple days, so…
2. From the fire perspective, the 2×4 is a 1000? hr fuel and the stick is a 10? hr fuel. So the moisture changes much more rapidly.
3. And it’s magic too!
Isnt the bark coming off the tree from a porcupine gnawing on it?
Not in this case, Karen. The bark split because of the heat of the wildfire and then is peeling off the dead trees over time. At some point, I’ll post a series of photos from this camera and you’ll be able to watch that process – it’s pretty neat.
I’m in the “barometric pressure” camp. A neighbor had a weather stick that predicted rain. It was a small irregular twig (8 inches or so) that was attached to a backing board that he mounted on the side of his garage. It did change position noticeably, even dramatically, when the weather was changing. Unfortunately, I didn’t do a study to record the barometric pressure and the stick’s position on a regular basis.
An enormous new species of Stipa seed with it’s awn trying to twist it’s way into the sand?
A bored Richard or Doug playing tricks with the cameras? (if I were them, I’d totally put on a big foot costume and make sure to get caught once or twice in those cameras).
If you compare a couple of the photos to each other, you can see the green vegetation seems to move as well. I’m in agreement that the movement is caused by moisture/humidity. The green vegetation seems to rise up as the humidity becomes less during the heat of the day? I’m sure the stick is affected similarly. Very cool to catch this on (what I’m assuming is) a game camera!
I’m in the humidity camp as well. Over the years, I’ve observed a number of natural “weather sticks” that move on the regular basis you observed here. Most of them were about pencil-thin twigs projecting out from tree trunks, but occasionally I’ve seen ones just lying on the ground responding the same way. Various purveyors sell “weather sticks” (one poster provided a link), and the explanation that seems to be most generally accepted to explain its movement relates to the moisture absorption and expansion qualities of wood (akin to Rex’s comment). Here’s a link to one website that talks a bit about it.
http://www.wordiq.com/definition/Weather_stick
As to the rapidity of the movement in response to humidity changes, those involved in prescribed burning will be acquainted with fuel size-classes, which are defined by the diameter of the fuels. 1-hour fuels, which are <1/4" in diameter, and similar in size to weather sticks, respond very quickly to changes in humidity.