September 7 Nature Walk

The second of the annual Detroit Audubon field trips to Eliza Howell Park takes place on Saturday, September 7, 2019, starting at 8:00 a.m. The public is invited; there is no cost.

Timed to coincide with the early days of the Fall bird migration, this walk give special attention to birds, especially warblers headed from the North Woods to Central and South America. Depending upon the weather conditions, we are likely to see several warbler species, perhaps including these three. (Thank you to Margaret Weber for these three photos.)

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Black and White Warbler

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Nashville Warbler

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American Redstart

The fall warbler migration begins at the end of August and continues into October, with individuals of some 20 different species making short stops at Eliza Howell. The find from one day to the next is almost always different.

If September 7 is a good day, the birds will keep us quite busy, but we will also stop for non-bird observations. This is about the best time of the year to note the variety and nature of spider webs among the wildflowers and the shrubs. They vary in sizes and shape; this is a small one on a thistle.

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September is also the month when I most frequently see a Praying Mantis (or 2 or 3). They have reached maturity and may be seeking mates and/or laying eggs. (I wrote about “Praying Mantis Egg Laying” on September 13, 2018.)

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Butterflies continue to be present. One of my favorite late-season butterflies is the Common Buckeye, which makes it appearance in Eliza Howell after the July butterfly peak.

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I usually find several Bald-faced Hornet nests in the park each year, beginning about this time. We may want to stop for a look (through lenses) to watch the hornets enter and exit the hole near the bottom of these amazing constructions. (For more, see “Bald-faced Hornet Nests,” December 12, 2017.)

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Blue Jays migrate in September and many spend days at Eliza Howell harvesting acorns, from the middle of September into October. (For more information, see “Blue Jays Harvesting Acorns,” August 27, 2018).

September 7 might be a little early to see them at work, but we will check (this photo also courtesy of Margaret Weber).

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The seasons repeat themselves, so it is possible to predict what might be seen at any given time of the year. But it is also true that every day is different and almost every walk includes an element of the unexpected. Such is the nature of nature walks. September 7 should be fun.

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Surviving the Winter? The Praying Mantis

This is a follow-up to the posting on September 13 this year – “Praying Mantis Egg Laying.”

Adult Praying Mantises do not live beyond the fall; the next generation is in the egg cases and will emerge in the spring. They will emerge if all goes well. Since September, I have been checking on egg cases in Eliza Howell Park.

My observations began on September 5, when I watched two different females lay their eggs. This is what the fresh new egg cases looked like then.

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That same day, I noticed a pair mating so was confident that those two egg cases would not be the only ones this year.

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In the weeks that followed, I many times walked the narrow path through the field of wild flowers and small shrubs/trees. I gradually saw more and more egg cases, especially when they became easier to see after the leaves dropped. These five were found in early November.

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As of now, I have located 11 different egg cases visible from that path. Almost all of them are on the small trees (buckthorn, for the most part) growing in the field. Since each egg case probably has dozens and dozens of eggs, 11 cases would suggest a large number of little mantises emerging in the spring. If all goes well.

Some of the birds that spend the winter in the park are insect eaters, birds that often seek insect eggs and larvae. Praying Mantis eggs, though protected in the oothecal, are vulnerable to birds with beaks that probe.

Recently, I have been seeing evidence of predation.

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Of the 11 egg cases I am aware of, 6 have been opened like this. And it is only November. The number of Praying Mantises estimated to emerge in the spring in Eliza Howell is decreasing rapidly.

While I have not directly observed this, I suspect that Downy Woodpeckers are responsible for invading these egg cases. Insect eggs are a part of their diet and they frequently forage on small trees and on plant stalks.

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Photo by Margaret Weber

Another threat to the survival through the winter is the weather. One of the eggs cases is on a goldenrod, a large perennial that typically does not stay standing all winter. Last week, during the first snowfall of the year, it was bent low by the heavy snow, but it came right back up when the snow melted. The first picture below is from November 9; the second from November 10.

The stem will get weaker as the season – and the snow — continues. I do not know how well developing Praying Mantises are likely to do when an egg case ends up on the ground, but there is a reason why they are placed off the ground when the eggs are laid.

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We know that only a very tiny percentage of acorns sprout. In July, I reported that very few, if any, of the toad eggs laid in the breeding pond left the pond as toadlets this year. It should not be a surprise if only a small percentage of Praying Mantis eggs laid this fall will result in live mantises in the spring of 2019.

 

Praying Mantis Egg Laying

Since my previous post on Praying Mantises in the park (“Praying and Preying,” September 4, 2018), I have found several more mantises and have watched them in different activities. I have seen a pair mating and two different females laying eggs. Their egg laying is fascinating.

Praying Mantis females produce both the eggs and the egg case. The case, called ootheca, looks a little like styrofoam. It is securely attached to plant stems and is about an inch long. The female fills the case with, perhaps, 100 to 200 eggs. In both egg layings I observed, the female had assumed a head-down position and the case was attached to the plant about four feet from the ground.

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When finished, she leaves the case in place, where, if all goes well, the eggs will survive the winter and the young will emerge in the warmth of spring. It will be more than 6 months before these young emerge. When they do, they will look like tiny versions of the adult. And they will have the same indiscriminate carnivorous habits – their first meal may be a sibling.

In the next picture, the female is just pulling away from the case, egg laying complete.

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It was hot when I watched these two females, but Fall is coming and the first frost is not that far away. Females usually die around the first frost. They are completing the life cycle – and starting the life cycle.

The ootheca hardens and turns a little darker shade. The next picture was taken 4 days after egg laying.

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Laying the eggs is lengthy process, which is not surprising when we realize that not only does the case have to be made for housing the eggs, but each egg is placed in a different chamber in the ootheca.

A few days after the observed egg laying, I spotted a third Praying Mantis egg case on a shrub. I do not know how old this one is, so do not know if the eggs had hatched, but the case had been broken into, perhaps by a bird.

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Since it was no longer functioning as a protective environment for eggs, I cut the ootheca open to get a better sense of its structure. Though the details are hard to see in this picture, it might provide some sense of the way the case is structured.

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Praying Mantis egg laying is not a simple process of laying eggs on a plant. As I observe what happens to the egg cases over the next months, I will likely learn more about the life cycle.

As I noted in my first post last December (“A Sense of Wonder”), Eliza Howell Park “provides an excellent opportunity for me to experience the natural world in its wonder and excitement and beauty, right in the heart of a major urban area. I continue to be excited by what nature presents in season after season.”

Recently, the Praying Mantis has been the latest “critter” to contribute to my sense of wonder and excitement.

 

 

Praying and Preying: Those Two Front Legs

I hadn’t seen a Praying Mantis all year in Eliza Howell Park until last week. Now I have found three. The species is Chinese Praying Mantis, the larger of the two species found in Michigan, about 3 and ½ inches long.

It often takes careful searching – or just happening to look in the right place at the right time – to find the camouflaged insect.

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They are called “praying” because of their habit of holding their front legs together in front of them, similar to a praying position some humans assume. This posture can be seen in the next picture, taken from the front.

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The Chinese Praying Mantis was introduced in this country in the late 1800s to help control unwanted insects, having long been recognized as very effective in catching and consuming many different insects.

The mantis is an ambush predator. Part of the feeding strategy is camouflage. The shape and color make them difficult to see when they climb small limbs. This one was positioned head down.

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Its “praying” position is also part of its hunting strategy. It can remain motionless for hours, if necessary, until prey comes close. Then it strikes with great speed. The same front legs that remind people of praying are extremely effective in preying.

Note the differences between the front legs and the other four.

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Mantises are carnivores. They eat insects (all kinds) and spiders, and sometimes small frogs and birds. They even eat other mantises. At times, the female eats the male that mates with her!

The front legs have spines (spikes) that assist in grasping prey, which they then eat alive.

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Mantises usually mate in September or early October and the female lays eggs which, as an egg mass in a case, survive the winter and hatch in the spring (May or June). The adults I saw these last few days have probably only recently reached full maturity. That fact, and the need to find a mate, may account for them being more visible at this time of the year.

It is always exciting to find a Praying Mantis in a park or garden. It is attractive, a little exotic, and has a very interesting life history. They can even look somewhat harmless…

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…but those front legs are deadly to other insects.