A Northwoods Almanac for September 10 – 23, 2010
Monarchs Migrating! GPS Found in Their Antennae
Every autumn an estimated 100 million monarch butterflies all across North America migrate south. Recent reports in Wisconsin indicate they’re on the move now. On September 5th, an observer along the west shore of Green Bay reported seeing thousands of monarch butterflies in migration. The same day, an individual in Milwaukee’s Veteran’s Park reported seeing many hundreds moving through, while a butterfly expert in Oshkosh went outside in her neighborhood from 11 a.m. to noon with her stopwatch and counted 350 monarchs in her sight as she stood in one location.
So, they’re on their way, a trip none of them have ever made before. The monarchs heading south now are the great-grandchildren of last fall’s migrating adults - no monarch makes the round trip to Mexico and back to the Northwoods. Yet this generation will find its way to the same mountains in Mexico that monarchs have presumably journeyed to for thousands of years.
The journey will take them weeks. They head southwest, funneling through Texas and finally assembling together in the 9,800 to11,000-foot-high mountains west of Mexico City.
Scientists still don’t fully understand how the monarchs navigate, given that the monarch's internal compass only provides them a sense of direction based on the sun’s position in the sky. But they also need a sense of location – how do monarchs know to stop migrating when they reach their winter home in Mexico?
In 2009, scientists discovered that the compass and clock mechanism that the monarchs use to orient themselves is located in their antennae. They determined this by removing the antennae from a group of butterflies and comparing the way they flew with a control population in a flight simulator. The intact butterflies all flew southwest, as normal, but the insects without antennae headed off in random directions.
In order to prove that the antennae contain both a light sensor and a clock (the “clock” adjusts their compass to where the sun is in the sky), the scientists then painted the antennae of one group of insects with black enamel paint and compared their behavior with that of a group whose antennae were coated with transparent paint. The group with the black painted antennae all flew together in the wrong direction, while those with the transparent paint were unaffected.
A side benefit to this study is that the researchers were able to show that the antennae have a number of functions beyond being odor detectors. They can function as ears, sensing sound and changes in barometric pressure, and now they are known to function as a timepiece.
If you want to follow the migration of monarchs, you can do so on the Web – go to Journey North at www.learner.org/jnorth/. Journey North also allows you to follow the hummingbird migration.
Hawk Migration
Hawks are also on the move south. To have the opportunity to see hundreds to thousands of hawks in migration, I encourage folks every year to visit Hawk Ridge in Duluth, which is considered one of the top three fall migration sites in the U.S. Mary and I are leading a trip to Hawk Ridge on September 17, but in order to have the best chance to experience a major migration day, you have to watch the weather. A northwest or westerly wind is the key, and the more days in a row, the better. The hawks also won’t fly in the rain– for the most part birds simply stay put if the wind is against them.
It’s not just hawks that fly over the ridge. On September 5th, they also counted 2694 non-raptors including 34 Canada Geese, 2 Common Loons, 5 Common Nighthawks, 1 Eastern Kingbird, 2 Philadelphia Vireos, 1713 Blue Jays, 7 Red-breasted Nuthatches, 14 American Robins, 193 Cedar Waxwings, 69 warblers of 6 species, 1 Scarlet Tanager, 5 Red-winged Blackbirds, 5 Rusty-Blackbirds, 334 Common Grackles, 1 Baltimore Oriole, 106 American Goldfinches, 1 Evening Grosbeak, plus the following first migrants of season: 1 Red-headed Woodpecker, 1 Yellow-bellied Sapsucker, 1 Ruby-crowned Kinglet, 1 Blue-headed Vireo, 1 Savannah Sparrow, 1 Lincoln's Sparrow, 1 Swamp Sparrow, and 1 Lapland Longspur
For information on Hawk Ridge, how to get there, and for their daily count listing, go to their website at www.hawkridge.org.
Bryozoa
Last week I had three different people on three different lakes contact me with a question that went something like this: “Would you know what the oblong, translucent, volley-ball size, gelatinous objects are that are washing up on our shore?” Mary Madsen in Presque Isle sent me several photos of one of these organisms that was growing on her livebox. What everyone is seeing is a colony of bryozoa, or what are called “moss animals.” I believe the genus and species is Pectinatella magnifica, but I’m certainly no expert on these creatures.
For most of us, bryozoa are rather incomprehensible. The colony resembles a stiff, clear-gray Jell-O, that is actually 99 percent water, and firm and slimy to the touch,
The surface is divided into tiny rosettes, each containing 12 to 18 “zooids.” If you could look through a microscope, the zooids have whorls of delicate feeding tentacles that sway slowly in the water and capture food.
Bryozoans feed on small microorganisms, including diatoms and other unicellular algae. In turn, bryozoans are preyed on to a limited extend by grazing organisms such as fish, and are also subject to competition and overgrowth from sponges and algae. They indicate good water quality and are utterly harmless.
Wild Rice
Rod Sharka reports that the wild rice harvest looks quite poor this year. He wrote to me on 9/6: “I think the hot, windy weather we had last weekend, followed by the rains this past week, hastened the ripening and shedding of the good rice grains. The rice worms and brown spot disease took care of the rest. After working for two hours gathering, we stopped to rest and I took time to take a close look at what we had harvested. I was disappointed to discover that about 80-90% of the crop consisted of "ghost" hulls. That is, they were empty of rice grains. There is probably more protein in our harvest in the form of rice worms, spiders, and other various critters than in actual rice.
“We also checked out Nixon Lake and Creek, which is one of the regulated ricing areas. Interestingly, the rice plants there were very short, barely tall enough to reach the gunwales of the canoe. There were more good grains there as it was not as far along in development, but the plants were not as dense as in Rice Creek, and due to their short stature, would have been very difficult to harvest.”
I haven’t heard from other ricers, but I suspect if these two traditionally excellent sites are fairing poorly, so is the rest of the rice in our area.
Sightings
Elizabeth Stone reported that her son Chris sighted three immature trumpeter swans on August 10 on Squaw Lake at the mouth of Stone Creek. Then on August 13, her daughter Lindsay and she saw an immature trumpeter on Squaw Creek near the Highway 70 dam. Elizabeth believes these may be the first trumpeter swans ever seen on the lake, and wanted to know if they were just passing through or possibly permanent residents of Squaw Lake.
I suspect it’s most likely that the cygnets had recently fledged from an off-site nesting location and were simply out enjoying a luncheon at a new lake. I’m uncertain what the average home range is for a trumpeter, but given that they are the largest waterfowl in all of North America and are strong flyers, I would imagine they feed at an extensive radius out from their nest site. Given that great blue herons are known to forage over 12 miles from their rookeries, trumpeters would certainly have the capacity to travel at least that distance.
They eat a very broad diet of primarily aquatic plants, consuming the leaves, stems, roots, and tubers of submerged, floating, and emergent plants, including: watermeal, muskgrass, pondweeds, naiad, milfoil, waterweed, watershield, bladderwort, wild celery, sedges, rushes, smartweed, pickerelweed, cattail, arrowhead, bulrush waterlily/spatterdock, wild rice, and on and on – basically just about anything that grows in the water. And they have a prodigious appetite, so they utilize numerous lakes and wetlands for foraging.
Celestial Events
On 9/11, look after dusk for Venus just above the crescent moon. Mars will be about five degrees north of the moon as well.
Autumn equinox occurs on 9/22 with the full moon (the Harvest Moon) occurring the next night.
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