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Autumn Snow on Mount Mansfield, Vermont © K.P. McFarland

A Field Guide to October 2020

October is a month of change. The forested hills fade from green to a kaleidoscope of red and gold that dazzles the eyes. Here’s your field guide to some moments that you might not otherwise notice during these few precious weeks that feature colorful hills beneath a deep blue sky, with calls of migrating geese high overhead and the last Monarchs gliding silently southward.

By Vermont Center for Ecostudies October 2, 2020
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Old claw marks on an American Beech tree. © K.P. McFarland
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Closeup look at a sedated bear's front claws. © K.P. McFarland

Bear Claw Scars and Tree Nests

By Kent McFarland

Keep an eye out for claw marks on American Beech tree trunks left by American Black Bear climbing into the treetops in search of beechnuts. When a bear finds a tree with a good quantity of nuts, it climbs up the trunk, parks itself in the canopy, and pulls nut-laden branches to its mouth. The bear often leaves a tangled ‘nest’ of bent and broken branches in the canopy where it has been feeding.

Black bears depend on body fat for the energy needed during hibernation. With protein content equivalent to corn (~11% dry mass) and fat content (~17% dry mass) that is more than five times that of corn, beechnuts are an important part of their fall diet. But the trees don’t produce lots of nuts every year. Beech trees normally have low yields one year, followed by bountiful nut production (called masting) the next year.

If you find signs of bear or areas with good beechnut production, be sure to snap some photos and submit your discoveries to the Vermont Atlas of Life on iNaturalist to help track these feeding areas and the crops the bears depend on.

American Beech husks and nuts. © K.P. McFarland
American Beech husks and nuts. © K.P. McFarland
October foliage viewed from the Okemo Mountain fire tower. © K.P. McFarland
October foliage viewed from the Okemo Mountain fire tower. © K.P. McFarland

Fall Leaf Peeping Season Advancing

By Kent McFarland

There are four basic colors in fall leaves and a different pigment produces each. Xanothophylls are responsible for yellow, carotenoids for orange, tannins for brown, and anthocyanids create red and purple tones.

During the growing season, green chlorophyll in tree leaves is broken down by sunlight and constantly replenished. As day length decreases, the abscission cells, a special layer at the leaf-stem junction, divide rapidly and slowly block transport of materials. As abscission begins, chlorophyll production wanes and eventually stops. As the green chlorophyll breaks down without replacement we begin to see the underlying orange carotenoids and yellow xanthophylls. These pigments help capture light energy during the growing season. But unlike yellow and orange pigments, red anthocyanins are made during fall leaf senescence. They are manufactured from sugars found in the leaf. They produce greater amounts during cooler nights and sunny days. When a hard freeze comes along, production ends.

Why would a tree use energy to make a pigment in a leaf that is about to die and fall off? In 2003 William Hoch, a biologist at Montana State University, found that if he genetically blocked anthocyanin production, the leaves were much more vulnerable to fall sunlight damage, and sent less nutrients to the plant roots for winter storage before the leaves fell. The tree was not able to recuperate as much energy back from the leaves it grew earlier in the year.

A few years later, University of North Carolina at Charlotte graduate student Emily Habinck found that in places where the soil was lower in nitrogen and other important elements, red maple trees produced more anthocyanin in the leaves. Apparently trees growing in more stressful environments invest in more anthocyanin, which allows them to recover more nutrients that are stored in the leaves before they fall. Bright red leaves under a clear blue sky are spectacular to see. But what is beauty to us may be survival to a tree.

A few years ago on Outdoor Radio, we met Joshua Halman, a Forest Health Specialist with the Vermont Department of Forest, Parks and Recreation at Underhill State Park where the department has monitored these trees for over 25 years, recording color change and leaf drop here and at other places around the state.

Halman told us that this work has documented the impacts of climate change. “Seen over this time, the peak color and the main time for leaf drop has actually become later,” Halman explains. “What we’re seeing since we started recording our fall phenology data is that, on average, foliage is peaking about eight days later over that 25-year period.”

Listen to the show

A male Sharp-shinned Hawk banded 6/7/19 at VCE's Mount Mansfield banding station. © Nathaniel Sharp
A male Sharp-shinned Hawk banded 6/7/19 at VCE's Mount Mansfield banding station. © Nathaniel Sharp

Some Sharpies Head South

By Kent McFarland

The autumn river of raptors migrating southward becomes dominated by Accipiters like Sharp-shinned and Cooper’s Hawks in October. Although not all individuals leave, many do. More than 11,000 Sharp-shinned Hawks were seen on one October day at Cape May Point, New Jersey as they pushed southward. Most overwinter somewhere in North America; however, some travel as far south as Central America, migrating thousands of miles between their breeding and wintering grounds. They are powered by a mix of flap-gliding flight and soaring on mountain updrafts and rising plumes of hot air. Recently, more Sharpies have been overwintering farther north. No one knows exactly why, but the popularity of backyard bird feeding may provide some Sharp-shinned Hawks the food they need to survive northern winters.

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Observations of Sharp-shinned Hawks reported to Vermont eBird. You can help track these and other birds by reporting your sightings, too.
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Observations of Cooper's Hawks reported to Vermont eBird. While they may be less abundant during migration than Sharpies, they are more frequently encountered year-round.

Sharp-shinned Hawk populations currently appear stable, after dramatic declines during the DDT pesticide era (mid-1940s to 1972). Recently, work by VCE has shown that individuals nesting in Vermont’s Green Mountains and a rare subspecies in the mountains of Hispaniola have high levels of mercury in their blood. Learn more from VCE’s Research Notes about this finding.

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Aspen Serpentine Leafminer Moth (Phyllocnistis populiella), a leafminer found on aspens, cottonwoods, and poplars. © Nathaniel Sharp
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The segmented body of this Mantura floridana larva is visible as it chews through the inner leaf layers of a woodsorrel. © Nathaniel Sharp
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Ophiomyia parda, a leafminer found on asters. © Nathaniel Sharp

Mazes and Mines

By Nathaniel Sharp

No, we’re not talking corn mazes here, though they may be a favorite activity during the harvest season in Vermont. Instead, I’d encourage you to take a closer look at the leaves around you before they fall this October, and you may find the miraculous, maze-like patterns of leaf mining insects.

The catch-all term “leafminers” encompasses four different orders of insects, and several thousand species, with new species being discovered and described in recent years. All of these insects spend part of their lives as larvae feeding on the inner layers of leaves, sandwiched between the protective layers of the leaves of a vast array of plant species. As they feed, they leave behind diagnostic trails that twist and wind, or radiate from a central point, and often are dotted with small dark specks of excrement (frass). Most leafminers are specific to one species, genus, or family of plants, and by noting the host plant and shape of the mine, curious naturalists can often reliably identify the leafminer they are looking at!

More than 150 species of leaf-mining insects have been reported to the Vermont Atlas of Life on iNaturalist, and there are certainly many more out there to be discovered. Some distinctive and commonly encountered mines to be on the lookout for this fall include the winding mines of Agromyza vockerothi found on blackberries, raspberries, and other brambles, the calligraphic wanderings of the Aspen Serpentine Leafminer Moth found on aspens, and the amorphous blobs of the Hazel Blotchminer found on the leaves of hazels.

To learn more about leafminers, there is no better place than Charley Eiseman’s blog, BugTracks, where you can find a wealth of information about these fascinatingly diverse insects. If you encounter these winding insect trails while admiring the leaves of fall, snap some photos and upload them to the Vermont Atlas of Life on iNaturalist and the North American Leafminers project, where, if you make note of the plant that was hosting the leafminer, experts like Charley and others will help you figure out what species you have found. Perhaps it will be a new species for Vermont, and it’s even possible that you could discover a species of leafminer as-yet unknown to science!

 

A Jefferson's Salamander peers out of a rodent tunnel. © K.P. McFarland
A Jefferson's Salamander peers out of a rodent tunnel. © K.P. McFarland

Salamander Spelunking

By Kent McFarland

In the spring Spotted and Jefferson’s salamanders crawl to vernal pools—temporary woodland ponds that fill with water but then dry out later in the summer, providing a fishless environment for larval salamanders—where they mate and lay eggs. But for 90% of the year these salamanders are elsewhere in the forest. Sometimes you can find them by flipping over a large stone or rolling a rotting log, but for the most part, they are tough to find.

Technology allowed VCE biologist Steve Faccio to easily spy on a salamander using miniature tags that emit a radio signal. With a radio receiver and small antenna, Steve could then monitor the salamander’s movements and locations.

Standing on a forest path near the site, Steve turned on the radio receiver and tuned to a salamander’s frequency. A faint, but audible “ping” sounded from the headphones. A few minutes later Steve was in the general area of the animal. The signal was strong, but he couldn’t quite pinpoint it. It turns out that the salamander was underground.

After an hour on hands and knees, Steve found the exact spot. A series of narrow, branching tunnels under the leaf litter and rotting logs held the prize. Steve was able to move just a few leaves and there it was peering out from a tunnel opening.

These salamanders can’t dig. They use shrew, mice, and chipmunk tunnels for refuge. In fact, the tunnels are so important to them that Steve could predict areas in the forest that would be used by the salamanders just by the density of mammal tunnels. Without small mammals, there were no salamanders to be found.

After tracking them to these surface tunnels all summer long, suddenly, with the chill of fall, the salamanders changed behavior. They entered more vertical tunnels that led deeper underground. By November nearly all of them were deep under the earth. The radio signal only traveled about two or three feet, so eventually the signals were lost. They had gone deep enough to escape the ground penetrating frost and spying by radio from above.

Comments (2)

  1. Hi Nathaniel,
    I’m taking Charlie’s leaf and stem miners class this fall through Eagle Hill. Fascinating!

  2. Tom Aversa says:

    Hey Steve,

    This sounds like great work. I wondered how small your transmitters are? If you are actively tracking the animals, I guess you are using VHS telemetry? Mind boggling. I am curious at how they are attached. My wife (you may remember Cheryl?) has been tracking wood turtles here, but they are capable of carrying a good size unit.

    Anyways, keep up the good work,
    tom

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