7-21-23 Day 3: lots and lots of data today

The day was forecasted to rain and storm with lightening, so we rearranged our original plans and decided on the following:

1. morning:  survey the small mammal traps
2. afternoon:  instead of hiking to site 9, we would instead hike to site 14, which was smaller, had less parameters to record (nest boxes and tree girth only), and was close to where we parked the cars, in case thunder storms arrived, and we had to get out quick.

So the day looked like this (out my hotel window first thing, yes, I feel like I’m in the Sound of Music)

We started out, and it was indeed looking omnious

But off we went to the small animal traps.  To get to the locations, we hike on a trail, and then we have to go off trail several hundred feet in distance and with elevation

Here is what it looks like once we are off trail, climbing

And here we are along one of the 6 lines, running horizontally to check the traps

Today, the traps were SUPER interesting.  One site had 15 captures, and the other site only had 1.  Apparently day 1 of the traps is usually the lowest number of captures, and the longer the traps are in the field the more likely a small mammal will pass by, so you get more and more captures.

Lots of bank voles, and and we even had a garden dormouse with a shortened tail (apparently when captured by a predator, a dormouse can release it’s tail like a lizard, but it is painful, and it does not grow back).  Some highlight photos

But the coolest capture of the day:  it was a recapture from the day before (we know by the tag number), and when we weighed it, it was 29g.  Jana had the data sheet said “are you sure?”  And so reweighing still, we have 29g.  We rechecked the tag number, and and it was correct.  But this bank vole weight 58g yesterday.  Turns out she was pregnant yesterday, but probably not today!!!!

One more data gathering of these two sites (72 total traps) tomorrow.

After lunch we hiked up to site 14, and did two types of measurements:  tree growth and nest box observations

Tree growth:  

An inexpensive yet effective way to measure the growth of a tree is to measure its girth (circumference).   This measurement is done here by using a dendrometer, which works by using a vernier scale.  The dendrometer measures the change in growth of whatever it is wrapped around, as long as it can stretch the spring that is part of the apparatus.  Therefore, after initially taking the measurement of the tree’s girth, you place the dendrometer around the trunk of the tree, and then measure the change (usually every month during the spring and summer).

To read this dendrometer, look at the picture above.

•  The measurement will give you two numbers:  a whole number, and then a decimal.
• To find the whole number, you take the line above the zero by the spring, then take the line and see where if falls on the scale above:  in this case, the zero line is between 61 and 62, so the whole number in this measurement is 61.
•  Now, it’s 61 point something (since the line falls between 61 and 62), so to find the decimal, look at all the lines above the numbers that are between 0 and 10, and see which lines falls EXACTLY on a line above (on the whole number scale).  Whatever that number is, it is the decimal.  I know it’s hard to see, but in this case it is 8

So the measurement is 61.8mm.  Muy bien!!!

In addition, when the trees are initially chosen a 10 meter radius is drawn around the tree, and its competitors are noted:  that is, what other plant growth is within 10 meters of our tree of interest (see below).  As you can imagine, this is SO much work, cataloging the different species of trees, bushes, and other plant life in this 10 meter radius.  Each plot we have worked has had 11 trees, so yes, so much work…

Nest Boxes

The other parameter we measured today (which we also did the other day, and basically every day) were the nest boxes.  Boxes for birds to nest in are placed in the area, and then are monitored for egg laying activity.  While most of the bird breeding season is done and the nest boxes are empty, we still must check all the nest boxes, and recently mice have been using the nest boxes, sometimes after the chicks have left, sometimes after killing the eggs or chicks…

The first thing we do is to take a multi-tiered pole and check to see if the nest box has anything in it (we just flip the door open from the ground using the pole).  If there is something (we really check to see if we see nest material – moss, grass, etc etc) then we take the box down.  Sometimes the box is really high, so a steady hand is key!

While most of the nest boxes were empty, we did find:

1. Two dormouse nests, but no mouse, so we weigh the nest material, and then dump it (because the box really isn’t for the mouse…)
2. A bee’s nest (we left that one alone…!!!!)
3. And to me, super interesting, a dead chick left in the box.  The sequence of photos

In this video, Uri (I just learned I’ve been spelling his name wrong this entire time, SORRY!!!) explains

Uri explaining possible scenario for dead chick in the box

This scenario is a real life example of something I teach every year, which highlights nicely math in science.

So….anyone who has taken Statistics hears over and over again how all natural processes following a normal distribution, and this chick dying in the box is no exception.  Each reproductive event in a bird is called a clutch, and in evolution, there are what we call selection pressures, and it is well studied that for birds, natures prefers clutches to undergo stabilizing selection, which follows a normal distribution

What does this mean??  Basically, when birds have a clutch, it is best for the birds to lay a “medium” number of eggs (in the middle), because if they lay too few, predators will decimate the entire clutch, and if they lay too many, then too many resources are used by the parents, as well as in-fighting by the siblings, which leads to weakened, or dead, offspring

So the dead chick in the box is likely a victim of a clutch that was likely either too big or too small.

Okay, I now leave you with some fun pictures to enjoy!

The group!!!  Photos by Candace

And then, more amazing pictures of the landscape (photos by Mike S)