Dragonfly Notes

by Carl Strang

Today I want to share some observations of dragonflies from last week. It was, as you know, stinking hot all week, reaching 100F on Thursday and Friday. In the late morning on Friday, with the temperature in the mid-90’s, I was taking an early lunchtime walk along the May’s Lake shore. I noticed that the black saddlebags all were flying in an unusual position.

All had this peculiar abdomen dip, which they held as they flew.

It was reminiscent of the obelisk posture, shown by a perched dragonfly pointing its abdomen up at the sun. This is thought to reduce overheating in the insect’s body. I wonder if the saddlebags, in that extreme heat, likewise were reducing the size of their abdomens’ exposure profile. They were among the largest dragonflies I saw that day, which further might increase their danger of overheating.

Earlier in the week I was walking through one of Mayslake Forest Preserve’s prairies when I saw a common pondhawk carrying a relatively large prey to a perch.

It had caught a smaller dragonfly, a female eastern amberwing.

Female and immature male pondhawks have such perfect grass-green camouflage that they are practically invisible when perched in prairies and meadows. They are sit-and-wait predators, zooming out to catch passing insects. This predation on another dragonfly is not so rare. I once saw one catch a calico pennant, a dragonfly larger than the amberwing.

Lessons from Travels: Box Turtles and Wood Turtles

by Carl Strang

My first job after graduate school was an assistant professorship at Dickinson College, a small liberal arts school in south central Pennsylvania. One of my responsibilities was to manage The Reineman Wildlife Sanctuary, a large privately owned piece of forested Appalachian mountain ridge. Herps were abundant there, and for research subjects I could have gone with either salamanders or turtles. Turtles had been a childhood love, and so I decided to see how two terrestrial species, the eastern box turtle and the wood turtle, were managing to coexist in that forest. Eastern box turtles were common in northern Indiana, so I was acquainted with them.

Eastern box turtle, Reineman Sanctuary

Wood turtles were new to me.

Wood turtle, Reineman Sanctuary

Most of the area was a forest growing on rocky soil.

Typical forest scene, Reineman Sanctuary, winter.

Lower areas were relatively level, but much of the property was sloping mountainside. The lowlands also were divided by streams that were intermittent to varying degrees but always had some pools. I caught as many turtles of both species as I could find, and notched the edges of their shells in patterns that allowed me to recognize individuals. I followed selected turtles in a decidedly low-tech way.

The plastic canister contains a spool of thread, which unwinds as the turtle walks along. I followed the thread to track the turtle.

The waterproof adhesive tape only held on for a short time, so the turtles were not carrying these backpacks into hibernation. I never found a sign that this device impeded or endangered them in any way. I was able to map and measure the turtles’ travels by taking up the thread. I also sat and observed them from a distance.

My principal findings can be fairly quickly summarized. Box turtles are thoroughly terrestrial, and they occurred throughout the Sanctuary, from the lowlands to the highest parts of the mountain ridge. They seldom contacted standing water, and this limited their activity. They had small home ranges. Much of the time they stayed buried in the leaf litter, coming out most predictably during rainy periods. They were visual hunters, and ate animal foods almost exclusively. When they did come out on dry days they did a lot of sitting and waiting for prey to move, and didn’t travel very far. The only times they covered a lot of ground were on rainy days.

These long-lived animals, submerged in the leaf litter, occasionally may be exposed to fire as may have been the case with this one.

Wood turtles were consistently active, and traveled far on dry as well as rainy days. They had much larger home ranges than box turtles. They ate both animal and plant foods, their most notable departure from the box turtle diet being their frequent consumption of green leaves. This added activity exposed them to desiccation, but they frequently entered streams during their wanderings, and sometimes remained in the water for days at a time. Since standing water was limited to the lowlands, wood turtles were limited to that relatively small portion of the forest.

The turtles revealed a clear tradeoff. Box turtles were widely distributed in space, but limited in the times when they could be active. Wood turtles were active all the time, but this tied them to the limited areas where they could reach open water. This significant impact of physical factors (water, humidity, temperature) was an important departure from the birds and mammals with which I had been most familiar, and a lesson I carry whenever I consider the reptiles and amphibians of northeast Illinois.

Eastern Bluebird Dossier

by Carl Strang

A couple weeks ago I shared my dossier on the great blue heron. Today’s choice is an example of a species for which I have not made a lot of observations, and so my personal knowledge is more limited.

Eastern Bluebird

As a child, occasionally I saw these at the horse-jumping practice ground in the Culver Military Academy’s Bird Sanctuary near Culver.

They nested in birdhouses mounted on posts in a tall-grass meadow with widely scattered trees at the Tyler Arboretum near Philadelphia in 1980.

I saw them in a similar area in spring 1986 at Waterfall Glen Forest Preserve, DuPage Co. I also saw them in southern Illinois at Giant City State Park. [Bluebirds once were so uncommon that simply listing the places where I had seen them was most of what I could write when I first created this dossier].

23MR88. A bluebird singing from the top of a nest box, one of those posted out from a fencerow. [Location not indicated; Blackwell?]

29AP90. Indian Knoll Schoolyard, near Winfield Mounds Forest Preserve. Bluebird foraging on mowed lawn by perching 8-15 feet up and sallying out 20-40 feet from perch to land on ground and take food, then returning to same perch or moving to another. [I since have concluded that this version of sit-and-wait foraging is their primary hunting method. Other birds I have seen hunting in this way are Australia’s kookaburras. Of course, the latter are after larger insects, small lizards, etc.]

20FE93. Bluebirds at the boundary between Hidden Lake F.P. and Morton Arboretum.

6FE99. Bluebirds wintering in a savannah area in the Morton Arboretum.

29AP00. Apparent territorial boundary dispute between two male bluebirds near prairie at Morton Arboretum. Song “peer, peer, poowee,” wings flutter when singing. Flying bird has an appearance like horned lark or swallow.

8OC00. Flock at West Chicago Prairie.

26MY01. A protracted dispute between a pair of bluebirds and a pair of tree swallows at a nest box in the prairie area at the Morton Arboretum’s Heritage Trail. The male bluebird was at the entrance on the outside of the box, with the female on the ground nearby, when the swallows arrived. At first it appeared that the swallows were attempting to chase the bluebirds away, but then the male bluebird became vigorous in chasing after the swallows. After 5 minutes of this, the bluebirds backed off and a swallow took the perch on top of the house. Soon, though, the bluebirds returned and the male resumed his attack. I never saw any of the birds enter the house.

5JA06. Fullersburg. A small flock of bluebirds feeding on honeysuckle berries near the Visitor Center bridge. (These stayed around for another week or so).

4AU09. Mayslake. Bluebirds nesting near the chapel have fledged at least one youngster.

(Dates are coded with the day, two-letter month code, and two-digit year).

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