A Northwoods Almanac for 9/11-24/26
Sightings: Nighthawks, Ladies Tresses, Lapland Longspurs, Fen Grass-of-Parnassus
Several people reported seeing common nighthawks migrating through our area in the last week of August. The largest count for nighthawks at Duluth’s Hawk Ridge occurred much earlier in the month on 8/16 and was “only” 1,400. For Hawk Ridge, this is a relatively low number - last year on August 22, 17,870 were counted funneling over the ridge and along the shore of Lake Superior.
Keep a watch out still - a few latecomers may yet be passing through on their way to South America and as far south as Argentina. Nighthawks migrate a great distance between their breeding range and winter range, making their journey one of the longest migrations of any North American bird.
On a hike in Powell Marsh on 9/2, Mary and I spotted several Lapland longspurs foraging along the dikes and giving us close views. Lapland longspurs breed in tundra habitats across the arctic, their name referring to the Lapland region of Scandinavia. We rarely see these birds in migration, so this was a treat.
We also found a small patch of nodding ladies tresses orchids (Spiranthes cernua) along one of the dikes in a spot we now watch for every year. I usually think of orchids as living in stable, older habitats, but this species is an early successional one, a lover of disturbed habitats and often persisting in mowed habitats. And that is exactly where we’re finding these - along a mowed dike.
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| nodding ladies tresses, photo by John Bates |
Mary and I traveled over to Petoskey, Michigan, in the last week of August to set up her “Women and Water” exhibit, and afterwards we walked in the Grass River Natural Area, a 1,502 acre nature preserve surrounding the Grass river. We walked 1.5 miles on wooden boardwalks traversing the northern fen and cedar wetlands - spectacular!
All that wetland harbors an immense array of wildflowers and birds, and we were thrilled to find numerous clusters of fen grass-of-parnassus (Parnassia glauca), a threatened species in Michigan. It’s not a grass, though its leaves resemble a grass. The gorgeous five-petaled white flowers just popped amongst the greenery of the fen.
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| fen grass of parnassus, photo by John Bates |
Hartwick Pines - Old-growth White Pines
We were also able to visit Harwick Pines State Park, which contains one of the most-visited old-growth forests in the nation. A paved 1.25 mile trail leads through a 49-acre remnant of Michigan's original forest dominated by remnant white pines.
In 1927, Karen Michelson Hartwick purchased over 8,000 acres of land here, which included 86 acres of old growth white pine. A short while later she donated the land to the State of Michigan as a memorial park to be named for her husband who died in World War I. She also specified the forest should never be logged.
Today Hartwick Pines covers 9,672 acres and is one of the largest state parks in the Northern Lower Peninsula. A windstorm in 1940 reduced the old-growth pines area from 86 acres to 49 acres.
Of course, I’d forgotten to bring my diameter tape, but many of the pines were at least three feet in diameter and provided a fleeting sense of what the original pineries likely looked like prior to the cutover.
Common Green Darners
When we think of fall migration, most of us think only of birds, but there are a number of species of insects that engage in remarkable movements, monarch butterflies, of course, being the most famous. However, several species of dragonflies fly long distances as well, and in great numbers.
The champion migrator among the dragonflies is the common green darner. In August, counters at Hawk Ridge tallied 4,277 passing over the ridge and heading south.
Their migration is somewhat similar to that of the monarchs in that it spans three generations every year. The first generation of insects emerges in the southern United States, Mexico and the Caribbean from about February to May, and then as early as March, they migrate north 500 to 800 miles to lay eggs in northern ponds before dying.
The new second generation that emerges from the ponds lives in our area all summer, and then migrates south from about July until late October, though they have never seen where they’re heading.
A third generation then emerges down south around November, and lives entirely in the south during winter. It’s their offspring that start the cycle again by swarming northward as temperatures warm in the spring. With a wingspan as wide as a hand, they devote their whole lives to flying hundreds of kilometers to repeat a journey their great-grandparents made.
How do scientists know where the green darners go? Remarkably, they can determine their hatch location by examining the chemistry locked in their wings. Stable hydrogen isotopes are ideal to infer where dragonflies were hatched because they reflect the latitude at which body tissues were grown. By vaporizing a segment of wing in a mass spectrometer researchers can find the chemical “signature” needed to determine latitude of the natal pond where a given dragonfly emerged.
A research team in Vermont spent two years using 21 years of citizen science data, more than 800 dragonfly wing specimens going back 140 years, and specimens caught in the wild to ultimately discern the three-generation migration system.
Amazing.
White-faced Meadowhawks
And then there’s white-faced meadowhawks, a non-migratory species, but one that can be seen in huge numbers in the early fall. On August 27, counters at Duluth’s Hawk Ridge, tallied 35,485 white-faced meadowhawks passing over the ridge!
Wow!
Of this moment, they wrote, “Late morning, an absurd number of Meadowhawks lifted off, boiling into a wall of dragons.”
“A wall of dragons” - I love that.
The next day, Aug. 28, they counted 1,754, and then another estimated 7,000 passed over the ridge on 9/2!
White-faced meadowhawk males are identifiable by a distinctive pure white face and red bodies, though females are usually yellowish or brown.
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| white-faced meadow hawk |
As I mentioned, they are not long-distance migrators! Rather, they move short distances away from water into fields, meadows, or forest edges to feed and find mates. Why were so many flying over Hawk Ridge and where were they were going? I don’t think anyone knows!
Monarch Migration
On August 23 as Mary and I were traveling east across the U.P. to get to Petoskey, we stopped in Manistique to take a walk along Lake Michigan. As we walked, we kept noticing monarch butterflies fluttering past us heading west along the shore, and it dawned on us that we were witnessing the early migration of monarchs heading south.
The monarch migration through the U.P. works like this. Every autumn during the last two weeks of August and the first two weeks of September, the monarchs gather at the Garden Peninsula or Stonington Point just east of Escanaba and Gladstone where they wait until the winds are right for the migration flight south across Lake Michigan to the Door Peninsula and Green Bay. They cross using the chain of islands running north off of Door County as stepping stones.
Once in Wisconsin, the monarchs travel another 2,000 miles or so to central Mexico where they aggregate in oyamel fir trees on south-southwest facing mountain slopes. These locations provide cool temperatures, water, and adequate shelter to protect them from predators and allow them to conserve enough energy to survive winter.
Unlike summer generations that live for two to six weeks as adults, adults in the migratory generation can live for up to nine months. In March, this generation begins the journey north into Texas and southern states, laying eggs and nectaring as they migrate and breed. The first generation offspring from the overwintering population continue the journey from the southern U.S. to recolonize the eastern breeding grounds, migrating north through the central latitudes in approximately late April through May. Second and third generations populate the breeding grounds throughout the summer. It is generally the fourth generation that migrate in the fall to the wintering sites in central Mexico about 3000 meters (almost 2 miles) above sea level.
How do millions of monarchs start their southbound journey from all over eastern and central North America and end up in a very small area in the mountains of central Mexico? They don’t learn the route from their parents since only every fourth generation of North American monarch migrates.
Since monarchs migrate during the day, it’s proposed that they use a sun compass. Monarchs may use the angle of the sun along the horizon in combination with an internal body clock (like a circadian rhythm) in their antennae to maintain a southwesterly flight path.
However, scientists have also suggested that monarchs use a magnetic compass to orient, possibly in addition to a sun compass as a “back-up” orientation guide on cloudy days.
Research showed that migratory monarchs indeed possess a magnetic compass using short wave UV-light that aids in orienting them south towards their overwintering grounds.
Along the way, the monarchs have to eat to provide the fuel for this arduous flight, and the nectar of jewelweed (Impatiens capensis) appears to be an important flower fulfilling that purpose. Which brings us to:
Jewelweed or Spotted Touch-Me-Not
Jewelweed currently bedecks many a wetland edge from here in the Northwoods all the way to the Gulf Coast. Its beautiful bright orange flowers have one of the sepals (outer parts of the flower) modified into a large, pouch-like structure with a long spur that is loaded with nectar. During late summer, these nectar spurs attract numerous hummingbirds, sphinx moths, and bumblebees, all of whom cross-pollinate the flowers.
But as fall comes on, jewelweed becomes essential to monarch butterflies. The monarch's long, flexible proboscis allows it to easily reach deep into the blossom to extract the nectar, and jewelweed nectar is exceptionally rich, boasting a sugar concentration of up to 43%. This is significantly higher than the nectar of many other late-summer wild flowers. The caloric density of jewelweed allows migrating monarchs to rapidly accumulate lipid (fat) reserves, which they store in their abdomens to fuel their long-distance flight all along the way to the Gulf.
Celestial Events - Autumn Equinox
The big celestial news in this time period is, of course, that autumn equinox occurs on 9/22. The sun now crosses the celestial equator (an imaginary line in space above Earth's equator) heading south. Official autumn has commenced, and longer nights than days become the rule.
Thought for the Week
“Essentially, autumn is the quiet completion of spring and summer. Spring was all eagerness and beginnings, summer was growth and flowering. Autumn is the achievement summarized, the harvested grain, the grape in the wine press . . . the bright leaf in the woodland . . . the froth of asters at the roadside . . . See it, smell it, taste it, and forget the time of year or day.” - Hal Borland, Twelve Moons of the Year
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