Thursday, December 18, 2014

Late-Season Dragonfly

Betsy and I visited Cranberry Lake every sunny day this Fall to see if any dragonflies were flying.  The last day we saw a dragonfly at Cranberry Lake was Thanksgiving, November 27.  On that day we saw two male Autumn Meadowhawks, which set a new record for a late flight date by one day.  They were perched in the sun, low to the ground, and the temperature was 55 ˚F.  Nice conditions, overall, though it was a bit breezy.  One of the meadowhawks flew upward, grabbed a flying insect, and landed to consume it, so they were still quite active.

Here's a photo of a male Autumn Meadowhawk:

This one is perched on the fence near the parking area, a favorite perching spot due to its exposure to the sun.

The weather has been so variable lately.  One day when we visited Cranberry Lake there was a fog bank around the shoreline of the island.  We decided to go out to Washington Park to see what it was like there.  Here's the view at Green Point:

At the top of the loop drive we were above the fog bank, and it was sunny and warm.  Here's the view:

Cranberry Lake is in the hills in the distance, above the fog on this day.  Birds were active at this lookout point, including a flock of 30 American Robins, 4 Varied Thrushes, and a single (naturally) Townsend's Solitaire.

Wednesday, December 17, 2014

Dragonfly Magazine

The Happy-face Dragonfly was featured recently on the cover of the (fictitious) magazine, Dragonflies.  Here it is.

Looks like a good issue.  Mr. Happy-face sure gets around!

Wednesday, October 22, 2014

Happy Birthday, Mr. Happy-face!!

An important day in my development as a Dragonfly Whisperer was October 22, 2006, when I took the first photo of the Happy-face Dragonfly at Cranberry Lake in Anacortes, WA.  I was just trying to get a good macro shot of the Paddle-tailed Darner's head, and had no idea what a delightful happy face it has until I brought the photo home and viewed at it on my computer.  That was eight years ago, and was the impetus for my continuing interest in dragonflies.

Here's the original Mr. Happy-face, still my favorite:

Here's another version of the Happy-face Darner, this one sitting happily on my finger:

Here's another view of a Happy-face Dragonfly.  This guy is smiling up at me from the bushes – so fascinating to look at a dragonfly and see this smiling face looking back at you!

Happy Birthday, Mr. Happy-face.

Tuesday, September 30, 2014

Six Splash-Dunks and a Spin-Dry

Here's a recent video from Cranberry Lake in Anacortes.  It was taken on September 28, 2014, and shows a series of six splash-dunks, followed by a spin-dry that sheds a lot of water drops.

The dragonfly in this video is definitely a darner, though it could be either a Paddle-tailed Darner or a Shadow Darner – these are the two darners flying at the lake now.

We saw 15 splash-dunk events that day, in about an hour of observing, with the number of splash-dunks ranging from 1 to 8.  This is the peak season for splash-dunking, but soon the activity will start to taper off.  Here's a plot of the splash-dunk activity per month for the last three years.

We haven't seen any sticking events yet, where the dragonfly gets stuck in the water.  As the temperature drops below 65˚ F we expect to see these events start to occur.

Just to fill in the details on the splash-dunk/spin-dry suite of behaviors, we present some of the key features below.

First, the basic idea is of splash-dunking is illustrated schematically below:

Here we see a dragonfly plowing into the water a number of times (six for the above video), for the purposes of cleaning its body.  In a splash-dunk, the dragonfly completely immerses itself in the water, and comes to rest for about half a second.  This is in contrast to getting some water to drink, where the dragonfly just barely touches the water, and keeps flying at normal speed.

After a series of splash-dunks, the dragonfly gains some altitude and performs a spin-dry motion at 1,000 rpm to shed the water – which often comes off in a visible halo of water droplets.  So just what is a spin-dry?  Briefly, it's a tumbling, head-over-heels motion, like a somersault, or a diver spinning on the way to the water.

There is a lot of confusion on this point, so to be specific, let's look at a dragonfly and its three principle axes of rotation:

The spin-dry occurs about the dragonfly's "pitch" axis of rotation – that is, the axis that passes along the length of the wings.  This gives the head-over-heels motion mentioned above.  A sketch of a spinning dragonfly is shown next:

Finally, it was mentioned that the dragonfly does its spin-dry at 1,000 rpm.  That figure is obtained by counting the number of frames of high-speed video needed for a rotation, and converting the result to revolutions per minute (rpm).  Here's a plot of data from a number of spin-dry videos:

The red line shows the average spin rate, which is just above the 1,000 rpm mark.  This spin rate results in a centripetal acceleration of about 10g, which is more than enough to throw off any clinging water.

These are the key features of splash-dunking and spin-drying.  With a keen eye, these events can be seen in realtime at your local lake or pond.

Thursday, September 11, 2014

Anacortes Field Trip: Saturday, September 13

Greetings Dragonfly Enthusiasts!

I can hardly believe how favorable the forecast is for this Saturday, September 13.  The weather's great, the dragonflies are out, and all systems are go!

Here are some details:

Field Trip Plans

1).  Start around 11:00 am at Heart Lake in Anacortes.  Heart Lake is right next to the road that takes you up to the top of Mt. Erie.  Meet in the southeast corner of the parking lot, which is the area farthest from the boat launch.

2).  Go to Smiley's Bottom around noon for a lunch break and to use the facilities there.  We will carpool at that location and proceed to Cranberry Lake.

3).  Arrive at Cranberry Lake around 1:00 pm.  This is where we hope to see some splash-dunking and spin-drying.  We'll probably finish up and return to Smiley's Bottom around 2:00 or 2:30 pm, depending on the activity level.

Here's a map showing the relevant locations:

To help you prepare for the field trip, here are photos of the damselflies and dragonflies most likely to be seen Saturday:

Clockwise from upper left: Spotted Spreadwing, Tule Bluet, Northern/Boreal Bluet, Pacific Forktail.

Clockwise from upper left: Paddle-tailed Darner, Paddle-tailed Darner (Mr. Happy-face), Shadow Darner, Blue-eyed Darner.

Clockwise from upper left: Cardinal Meadowhawk, Autumn Meadowhawk, Four-spotted Skimmer, Eight-spotted Skimmer.

Clockwise from upper left: Blue Dasher (male), Blue Dasher (female), Western Pondhawk (female), Western Pondhawk (male).

We look forward to seeing you this Saturday!