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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Less Frequently Photographed

The appearance of colorful butterflies, birds, and flowers often brings out the camera, but many less visible or less colorful living park features do not get similar attention. During my walks in Eliza Howell Park in the second week of August this year, I have been making an effort to get pictures of some less frequently photographed insects and spiders.

A large number of dragonflies are now flying in the park. It is difficult to get a good image of one since they seem always to be on the move, rarely resting long enough for me to get a picture, but I am beginning to get a few.

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There are, I think, over 300 different species of dragonflies in the United States and Canada and I am not (yet) prepared to attempt species identification of most of those I am seeing. For now, it is enough to see some of the variety and to have a few pictures with enough clarity that some body features can be noted and appreciated. Dragonflies are predators, eating other insects.

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Every year in late summer, I see webs that cover the tips of some tree branches. These “tents” are the home of the larvae (caterpillars) of a moth called Fall Webworm. I hardly ever see the white adult moth, but the tents where the larvae feed on leaves are easy to find. Though the trees lose some leaves, the webworms do not appear to do any long-term damage to the trees.

Since the larvae can usually only be seen within the webs, it is difficult to get a good picture of them. I have not yet done so.

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Grasshoppers are also in abundance in EHP now, especially easy to find along the walking path within the road loop. They are usually seen “hopping” away from where one is walking, not waiting to have their picture taken. I have a little more success finding them at rest in foliage. Grasshoppers are herbivores, feeding mainly on leaves.

The over 600 species are often in shades of brown and/or green. I am just beginning to get a sense of the variety within the park.

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Similar to the case of dragonflies, pictures can help me gain appreciation for some grasshopper features by allowing for close-up looks without catching them.

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August is the beginning of spider web season. Last year — September 20, 2018 — I wrote about the Banded Garden Spider (Banded Argiope) and its orb web. I have now found another orbweaver, the closely related Black and Yellow Garden Spider. It has been present in the same location for days, waiting for insects to get caught in its intricate web largely hidden in the wildflowers.

Large and colorful spiders like this are photogenic, but they are not frequently photographed simply because they are not frequently found.

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I confess that I have also been taking many pictures recently of butterflies and flowers, both of which have been plentiful and brilliant this month so far. But I do not want to neglect those “critters” that I know less well and photograph less frequently. There is so much to observe, to learn, and to admire.

Banded Garden Spider and its Web

Ever since a Banded Garden Spider (Banded Argiope) hung its web in our garden many years ago, it has been one of my favorites. Now is the time of the year to watch for webs and to find this and other spiders. Many spiders mature in late summer and the early morning dews highlight webs that we might otherwise miss.

Earlier this week I spotted this Banded Garden Spider in Eliza Howell Park while I was walking through the wild flowers.

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These spiders wait in the middle of the vertical orb web, in an inverted position, and hold their legs together so that, at first glance, it looks like they have only four legs instead of eight. They can feel when an insect is caught in the web and hurry to subdue it and wrap it in silk for eating later.

Many other spiders hide at the edge of their webs. The fact that Banded Garden Spiders position themselves at the center of the web, together with their practice of remaining on the web for much of the day, contributes to my observation pleasure. It has poor vision so one can come close without disturbing it, as long as they cannot detect an intruder with their other senses. It tends to drop down when there is contact with the web or with the branches that support it.

The web is large and basically circular. Banded Garden Spiders are among the spiders known as orbweavers and the webs are called orb webs. These spiders are large, but note how small they look in the center of the full web.

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The spider in the middle here (difficult to see) looks different from the one in the first picture, but it is the same one. Since it is on a vertical web, it is possible to view both its top side and its underside. We are now looking at the underside.

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Located on the underside, near the rear end of the abdomen, are the spinnerets, the external ends of the silk glands.

Large orb webs, especially when visible with dew drops, provide an opportunity to note the different threads. The radii threads (spokes) that go from the outside toward the center of the web are not sticky, but the spiral threads are – and are the ones that capture and hold the prey.

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This orb web, made by another orbweaver, not a Banded Garden Spider, shows the typical orb web shape.

In the next picture, a close-up of a Banded Garden Spider and part of its web, one can see that the sticky threads do not touch the center, where the spider waits. When an insect is caught, the spider travels to it on the radii to subdue it.

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Not all orbweavers incorporate the zig-zag looking arrangement near the hub (“stabilimentum”) in their webs, but Banded Garden Spiders do. The stabilimentum was visible in the pictures above and is shown again here.

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The function of the stabilimentum is not fully understood. While areneologists (spider experts) seek to learn more about this part of the web, the rest of us might notice it and wonder what the spider knows that we do not.

I am very far from being an areneologist, but my appreciation of the world of spiders is greatly increased by having access to some of their work, including this 2018 book.

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There are other types of spiders and other kinds of webs present now in Eliza Howell Park. This is the best time of the year for web watching – from now until the fall frost.