Saturday, November 30, 2013

Splash-Dunk Events For 2013

Well, the dragonfly season for 2013 is drawing to a close.  We're still hoping to see an Autumn Meadowhawk one day, if the Sun comes out, but the darners are long gone, and with them the splash-dunks and spin-drys.

It's time, then, to collect the data for this year.  Below is a chart showing the number of splash-dunk events seen this year as a function of the date of observation.

Notice the roughly "normal" distribution about the peak centered at September.  I knew September was a good month for splash-dunking, but hadn't realized how much it stands out from the other months.

Most of the splash-dunk events were observed at Cranberry Lake, and most involved darners, like the Happy-face Darner (aka the Paddle-tailed Darner) depicted to the right.  This is a "stick figure" I produced from a photo of a Happy-face – so the proportions are correct.  I plan to use this image to illustrate "wing grabbing" when attaching in tandem, as well as other behaviors.

Friday, November 15, 2013

I Looked For It

One of my favorite literary characters is Sherlock Holmes.  I've often wondered what it would have been like if Holmes had taken up birdwatching instead of beekeeping. A birder with the sharp observing skills of Sherlock Holmes would be something to behold.

Sherlock Holmes in the field.  Looking for birds?  Dragonflies?

I can just imagine an exchange between Holmes and Watson going something like this:

Watson:  Look Holmes, a Hutton's Vireo.
Holmes:  If you look closely, Watson, I think you will find that it is actually a Ruby-crowned Kinglet.
Watson:  Why do you say that Holmes?
Holmes:  Elementary my dear Watson.  Notice the yellow feet, the delicate bill, and the light wing bar with a distinct black border, all sure signs of a kinglet.
Watson: By Jove, Holmes, you're right.  I just saw it flash its ruby crown.

The other day I had a chance to repeat a famous line from the Holmes canon in the context of dragonflying.  It was fun.  The line, basically, is "I looked for it," and it occurs in a couple Sherlock Holmes stories.

One example is in Silver Blaze, which is actually more famous for the following exchange:

Gregory (official police detective): "Is there any other point to which you would wish to draw my attention?"
Holmes: "To the curious incident of the dog in the night-time."
Gregory: "The dog did nothing in the night-time."
Holmes: "That was the curious incident."

Later in the story, Holmes lies on the ground and searches through the mud, finally finding a crucial clue – a small match.

Holmes on the prowl for clues.

"I cannot think how I came to overlook it," said the Inspector, with an expression of annoyance.

"It was invisible, buried in the mud. I only saw it because I was looking for it."

Ah, he looked for it.  Exactly.
A similar exchange occurs in The Adventure of the Dancing Men.  A key part of that adventure is a coded message written with dancing men, as follows:

At one point Holmes and a police inspector are investigating the scene of the crime when the following conversation ensues:

“… there are still four cartridges in the revolver," said the inspector. "Two have been fired and two wounds inflicted, so each bullet can be accounted for."

“So it would seem,” said Holmes. “Perhaps you can account also for the bullet which has so obviously struck the edge of the window?”

He had turned suddenly, and his long, thin finger was pointing to a hole which had been drilled right through the lower window-sash, about an inch above the bottom.

“By George!” cried the inspector. “How ever did you see that?”

“I looked for it.”


In my case, I was dragonflying at Cranberry Lake, when I saw a Happy-face Dragonfly in the bushes.  It looked like this:

A male Happy-face Darner smiling up at me.

A man walking by saw me looking intently at the bushes.  He stopped and asked, "What do you have there?"

"A dragonfly," I replied.

"Oh, really? Where is it?"

"Right here," I said, pointing into the bushes.  It took some time to help him find it in the tangle of branches.

When he finally found it he stepped back, looked at me, and said, "How did you ever find it there?"

"I looked for it," I said.

Monday, November 11, 2013

A Late Meadowhawk

On October 6, Betsy and I went to Magnuson Park in Seattle for a little dragonflying.  We weren't expecting too much that time of year, but it was a nice day, and we thought we might as well give it a try.  We found quite a few darners and spreadwings, as we expected, so it was a fun outing.

To our surprise, we also found some Cardinal Meadowhawks out and about.  They are one of our first meadowhawks to appear.  In fact, they show up in early May, well before most of the other common meadowhawks in our area.  We hadn't expected to see them this late in the season, and a check with the calendar of flight dates showed that the latest date previously reported for the Cardinal Meadowhawk was October 2.  Here's a look at the flight season for Cardinal Meadowhawks, including our modest extension to October 6:

Another way to look at the flight season is shown below.  In this graph, we plot the probability a Cardinal Meadowhawk will be seen in a given month.  For example, notice that about 40% of the Cardinal Meadowhawk observations are made in the month of July.  The data for this plot are taken from 3 successive years of observations.

Even though it was late in the season, the Cardinal Meadowhawks were in prime color – which means intense red.  Here are a couple photos from October 6:

A male Cardinal Meadowhawk.  Notice the dark red color at the base of the wings.
Brilliant red on a sparkling, sunny day.  The dark red in the wings is nicely visible, but the wings make it difficult to see the white dots on the side of the thorax.

Cardinal Meadowhawks are primarily a west coast species, as you can see from the following dot map:

Even in our part of the country, they tend to be more common in the west:

When identifying meadowhawks, remember that Cardinal Meadowhawks are our only meadowhawk with a dark red concentration of color near the base of the wings.  This field mark can be seen from virtually any angle, which is often not the case for the white spots on the side of the thorax, and is quite definitive for this species.

Wednesday, November 6, 2013

Cumulative Splash-Dunk Data

Betsy and I have been observing splash-dunks and spin-drys for the last few years.  To date, we've observed 338 splash-dunk events, which we define as a case where a dragonfly (usually a darner) plunges into the water one or more times to clean itself.  When we see an event, we count the number of successive splash-dunks that occur.  The total number of splash-dunks we've observed is 780.

The maximum number of splash-dunks observed in a given event is 8 – at least, so far.  This particular observation is described in the The Case of the Constipated Darner at the following link:

Here's a histogram of our combined results for 2011, 2012 and 2013:

The average number of splash-dunks per event (2.31) and the least-squares fit to an exponential have changed very little from last year's results.  Here's the analysis of the data:

Overall, the drop off in the number of events is roughly exponential, though there appears to be a larger number of three splash-dunk events than one might expect – a bit of a "shoulder" in the data there.  We'll see how these results evolve as more data is collected.

Saturday, November 2, 2013

A Six Meadowhawk Day

Last week, October 23 and 24, Betsy and I went to the Sun Mountain Lodge in Winthrop, WA to enjoy the Fall colors for a couple days.  It was beautiful there, as you can see in these photos:

Sun Mountain Lodge from our room.
The Fall colors were in full effect.
A Golden-crowned Kinglet gave me an opportunity for a quick snapshot.

We went to the Beaver Pond, of course, but weren't expecting that much dragonfly activity.  We would have been happy to see a few.  As it turned out, the activity was very good, with lots of darners patrolling the shore looking for females, and meadowhawks flying in tandem over the water, dipping and laying eggs.  In some areas, each step would flush several meadowhawks from the ground into the air.  It was delightful.  We had a six meadowhawk day, with the following species:

White-faced Meadowhawk
Striped Meadowhawk
Saffron-winged Meadowhawk
Band-winged Meadowhawk
Black Meadowhawk
Autumn Meadowhawk

A six meadow hawk day would be good in the summer, but was especially pleasant to experience this time of year.  The most common species was the Saffron-winged Meadowhawk.  We saw only one White-faced Meadowhawk, and it set a new record late date by 16 days.  Here are pics of the meadowhawks:

White-faced Meadowhawk.
Striped Meadowhawk.  An older individual with frayed wings and faded stripes.
Saffron-winged Meadowhawk on the left, and Band-winged Meadowhawk on the right.
Black Meadowhawk.  We don't see Black Meadowhawks all that often, so this one was a particular treat.
Autumn Meadowhawk.  One of the "field marks" for Autumn Meadowhawks is that they land on you.

As usual, we had a great time at the Sun Mountain Lodge and the Beaver Pond.