NWA 9/2/11

A Northwoods Almanac for September 2 – 15, 2011

Nighthawks Migrating

Mary and I observed a small flock of nighthawks migrating through Manitowish during the early evening of 8/26. While nighthawks migrate both day and night, most flights are observed during the early evening. The great distance they travel between their breeding range in North America and their winter range in central and southern South America makes their flight one of the longest migration routes traveled by any North American bird.

Their fall departure begins as early as July and individuals become quite social, occasionally gathering in flocks of thousands. They fly rapidly with no apparent leader, typically close to the ground, and often with wingbeats in unison.

Nighthawks leave our area early, because they require a constant supply of flying insects which are only available during warm weather. Thus they have no choice but to stay at least one step ahead of the first frost.

Hummingbird Migration

Several individuals stopped me last week (8/22-26) to ask if hummingbirds had already begun migrating, because it seemed to them that about half of the hummers at their feeders had left. Several others, however, told me their numbers are still stable, and they are filling their feeders continuously as the hummers tank up for migration.

Both situations make sense. We usually think of “our” hummers leaving by around September 10^th, but it’s not a uniform departure. Some male hummingbirds start migrating south as early as mid-July, though their peak of southward migration is late August and early September. Many people notice that adult males migrate earlier than females, because in the last month or so there may be no birds with red throats at feeders. The males precede females in both spring and fall migrations, while the juveniles of both sexes lag somewhat behind adult females in fall.

Hummingbirds may begin to accumulate fat in early July, and their  body weight can double in as few as 7 to 10 days. If a larger bird gained that much weight, they would not be able to get off the ground. It’s during this time you may notice a hummingbird swarm around your feeders.

But by mid-September, essentially all of the ruby-throats seen at local feeders are migrants from further north coming through our area. The number of birds migrating south may be twice that of the northward trip, since it includes all immature birds that hatched during the summer.

The juvenile hummers fly alone and have to find their own way south. But the following year, each hummingbird will follow the same path or fly zone they did when they first made the trip. The best analogy I have heard is that hummingbirds are like commuters on a freeway, all going the same way on the same road, but doing so alone to get to their own individual homes.

While migrating, hummingbirds generally will fly during the day and sleep at night. Adult ruby-throats have a mass of only 3.5 grams on average (about one-tenth of an ounce), but despite their tiny size, many of these birds fly nonstop across the Gulf of Mexico during fall and spring migration, a round-trip of nearly 1,000 miles. Despite all the research done on hummers, their migratory routes remain poorly documented, and some proportion of the population appears to follow a coastal route south during the fall.

Ruby-throats have been documented arriving in Costa Rica by late September to early October. Remarkably, their overland migration occurs at nearly the same time as the peak flowering of jewelweed (Impatiens biflora), suggesting to researchers that the timing of jewelweed flowers may influence the timing of hummingbird migration.

Coyotes

            The North Lakeland Discovery Center hosted an exceptional talk given by Dr. Stanley Gehrt on his 10-year research on coyotes living in Chicago. I highly recommend you visit his website at www.urbancoyoteresearch.com to peruse his findings. His study has been call “the most ambitious work of its kind in the country,” and I believe it. Dr. Gehrt estimates that there are 2,000 coyotes living in Chicagoland among 9 million people, and the vast majority of people have no idea that they’re there.

            One of his major findings from his 250+ radio-collared coyotes, and one that should interest many people, is that coyotes prey on Canada goose nests and appear to be a major controlling factor on their urban population. He showed video footage of a coyote scaring off a nesting pair of geese, then eating some of the eggs, and carrying off the others. However, most of the coyotes in the study were found to be feeding on rodents and rabbit.

Loons Congregating

            Loons typically start socializing in the late summer/early fall, often gathering together on large lakes in surprisingly big numbers prior to migration. Terry Mann from Cassian sent me a photo of what he estimated to be about 100 loons on 8/20 on Pequot Lakes, Minnesota.

            In our area, Fence Lake, Lake Tomahawk, and Trout Lake are best known as potential gathering sites for large flocks of pre-migratorial loons. The adults migrate independent of their chicks and of each other. Fall migration generally begins in September, peaks in early-to-mid-October, and by late November most migrants have arrived in their wintering areas.

Mourning Cloak Butterflies

            We’ve had numerous mourning cloak butterflies puddling and basking in our driveway recently, and Mary got a few pictures that display their remarkable beauty. All butterflies prepare for the winter by either laying eggs before they die, overwintering as larvae (caterpillars), overwintering as pupae, partially migrating, or in the case only of the monarch, migrating completely out of their summer range. The mourning cloak is one of the few butterflies that chooses yet another strategy, overwintering as an adult, and in the process winning the butterfly longevity contest by living up to eleven months. The mourning cloaks hibernate under loose bark, in logs and in woodpiles, waking in early spring to emerge as the first butterfly of spring.

Sturgeon Jumping

            Mary and I recently led a group of paddlers from the River Alliance of Wisconsin on a section of the Manitowish River. Twenty canoes and kayaks comprised our little navy, and we were blessed with a picture-perfect late summer day in the Northwoods. Perhaps our most interesting sightings of the day were sturgeon jumping on four different occasions on Benson Lake. Why these very large fish fling themselves from the water is unclear – perhaps they’re seeking to dislodge leaches or some other parasitic organism. George Becker in his classic book “Fishes of Wisconsin” notes: “Lake sturgeon have the habit of leaping entirely out of the water until they appear to be standing on their tails. Sometimes just the head and upper third of the body slides up and out of the water at a forward angle and falls back, creating a sliding splash. This leaping action may serve to get rid of parasitic lampreys attached to the sturgeon. Twenty-seven lampreys were removed from one 62-inch sturgeon in Lake Winnebago. The lampreys probably do little damage, but they must be a nuisance.”

            We don’t have lampreys in the Manitowish, thank God, so perhaps they are leaping simply because they can. Regardless of their purpose, they create a lot of excitement when one five-feet long jumps from the water!

Celestial Events

            The full moon occurs on 9/12. Called variously “The Harvest Moon,” “The Acorns Moon,” and “The Leaves Changing Moon,” it marks the last full moon of the summer – we’re moving fast toward the autumnal equinox on 9/23.

8/19/11

A Northwoods Almanac for August 19 – September 1, 2011

Mergansers Families

Jane Flanigan sent me a photo of an adult red-breasted merganser with 16 young, wondering if this was a normal clutch size or merganser day care. The average clutch size is 8 to 10 for both red-breasted and common mergansers, or at least so says the books. A clutch of 16 usually means a combined family. However, "egg dumping" sometimes occurs where a female will lay her eggs in another female’s nest, and thus one female can end up with a big clutch like this.

Long Distance Journeys

By now everyone has likely heard about the “St. Croix, Wisconsin” cougar that was killed in Connecticut after walking over 1600 miles from its probable origin in the Black Hills of South Dakota. The cougar was struck by a car in Connecticut this June and was confirmed through DNA tests to be the same cougar that travelled through Minnesota and Wisconsin in 2009-2010. The 140-pound cat was hit on a highway in Milford, Connecticut, just 70 miles from New York City.

             The St. Croix cougar was first detected in Champlin, MN on December 5, 2009, about 15 miles northwest of downtown Minneapolis. It was last detected by the Wisconsin DNR near Cable, WI on February 27, 2010. The straightline movement of the St. Croix Cougar from its initial detection in Champlin to Milford is 1,055 miles, but if it had traveled through the UP and through southern Ontario, the shortest distance would have been about 1,150 miles. And since the St. Croix cougar was already nearly 500 miles from the Black Hills of South Dakota, his most likely origin, his actual straight-line move was likely well in excess of 1,600 miles. This movement of a large carnivore sets the record for straightline distance – the previous record for a dispersing male cougar was 663 miles from the Black Hills to Oklahoma.

            This is an amazing story for a mammal, but some fish might not be terribly impressed. Consider lake sturgeon. In November of 1994, a five-foot-long lake sturgeon was caught in a commercial fisherman's net in Saginaw Bay, MI, and was traced by its aluminum tag to have begun its journey from Lake Winnebago, 450 miles away where it had been tagged in October of 1978 by the WDNR. What makes this journey particularly remarkable is that the sturgeon had navigated the lower Fox River, which has 14 dams and 17 locks on it, before reaching Green Bay, and then wandered through Lake Michigan, the Straits of Mackinac, into Lake Huron, and finally down the east coast of the Lower Peninsula to Saginaw Bay. In those sixteen years, it had grown 8 inches, an average rate of growth for sturgeon.

That’s remarkable indeed, but another sturgeon was taken in Lake Erie five years after it had been tagged in Lake Winnebago, a distance of 850 miles away.

Much further afield, humpback whales travel 10,000 miles in their annual journeying, feeding during the summer near polar oceans and migrating to warm tropical oceans for the winter, making the cetaceans the farthest-migrating mammal on Earth. The distance is made all the more impressive given that the huge mammals follow nearly straight paths for weeks at a time despite surface currents, storms and other disturbances. A seven-year satellite transmitter study showed that the humpbacks never deviated more than about 5 degrees from their migratory courses, and in about half the segments mapped by the researchers, humpbacks deviated by one degree or less. The researchers concluded that the whales are orienting with something outside of themselves, not something internal. But Earth’s magnetism varies too widely to explain the whales’ arrow-straight patterns, and solar navigation requires frames of reference that water doesn’t often provide given that the open ocean is an endless horizon of blue. The researchers believe humpbacks rely on both magnetic fields and the sun, and perhaps the position of the moon and stars.

             What about birds? Well, there’s the great snipe, a relative of the Wilson’s snipe, a commoner in our area. The great snipe is a small, stocky shorebird that takes the fastest long-distance, nonstop flights of any animal not in an airplane. During its annual migration, a single snipe may fly for 96 consecutive hours, covering more than 4,000 miles. That’s four days without stopping or sleeping, sometimes at average speeds of 50 miles per hour.

While the longest known nonstop flight was made by a godwit that flew 7,145 miles from Alaska to New Zealand in nine days, its average speed was “only” 35 miles per hour compared to the great snipes’ which topped out at 50 miles per hour. Making the great snipes’ speed even more impressive was that it was done without wind assistance. When the researchers cross-referenced the flight records with wind records from U.S. satellites, they found little evidence of tail winds. Add in the fact that this was accomplished despite their rather rotund body and the relatively non-aerodynamic shape of their wings. Instead, the snipes seem to rely on massive stores of fat accumulated during autumn binge eating.

Lastly, there’s the sooty shearwater, which travels almost the entire stretch of the globe. Recent tagging experiments have shown that birds breeding in New Zealand often travel 40,000 miles (that’s not a misprint) in a year, reaching Japan, Alaska and California, and averaging more than 300 miles per day.

So, a cougar travelling 1,600 miles to Connecticut? It’s certainly a big deal, but a few other animals might see it as just pedestrian.

Mystery on the Cisco Chain

I need help figuring out this mystery. Mary Congdon, who lives on the Cisco chain in the U.P., wrote: “After a hard, sudden electrical storm (which clears quickly), the cisco are found floating on their sides on the water surface with their gills fluttering. They can then be scooped up in a net. If, however, one accidently bumps them with the net and misses, they immediately awaken’ and go to the bottom. If they are left there for a while, they will also go back down. We have lake trout at those same deep depths which do not react in this manner. I have always been curious, but never could get an answer, as to why this happens.”

Do any of you have some insight?

Migration Has Begun

            Mary and I spotted several greater yellowlegs on Powell Marsh on August 12 along with a flock of smaller shorebirds that were too distant to identify. So, shorebird migration has begun, and though our area is generally not known as a hotspot for shorebird stopover habitat, small numbers do appear along the shorelines of many of our lakes, river, and wetlands.

Migrants are not only coming through from the north, but many nesting birds in our area have already begun their exodus south. The black terns, bobolinks, and tree swallows that nest at Powell were all gone. These three species usually depart our area by mid-August at the latest, as do many of the neotropical warblers. Really, any bird species that relies exclusively on a diet of insects is getting ready for migration or has already left, because the first fall frost can occur anytime now.

            Keep an eye out for common nighthawks moving south – a birder in Wausau reported seeing a flock of 50 moving south on 8/14. The last two weeks of August are traditionally our most active migration periods for nighthawks.

Jewelweed in Flower

            Jewelweed is flowering in the moist soils separating wetlands from uplands. Hummingbirds work the tubular flowers during the day; at dusk, hummingbird moths take over the nectar patrol. Both types of hummers pollinate the flowers by picking up grains of pollen from the top front of one flower and depositing them on the next.

            The “jewel” part of the name is most apt, because of the spurred flower shape and orange color. Some folks see the dangling flowers as jeweled earrings, while others see jewelry in how the edges of the leaves sparkle with drops of water after a rain.

            The fruit pods give it another set of names, from “touch-me-not” to “poppers.” The pods pop open when touched, the outer covering uncoiling like a spring and shooting the seeds 4 to 5 feet through the air.

            For anyone suffering from poison ivy, boil the leaves, stem, and flowers of jewelweed in water until the water turns deep orange. Or crush the stem and just apply the fluid. Many people swear by the decoction as a cure for the evil ivy.

Lake Superior Swimming

            Mary and I led five consecutive days of hikes for Nicolet College last week, and on one of the days, the temperature reached 88°. We were hiking in the Porcupine Mountains State Park, so when we reached the trail’s end, we thought we’d cool off in Lake Superior, a dicey proposition given the usual frigidness of the world’s largest lake. If you don’t know the statistics, Lake Superior contains almost 3,000 cubic miles of water, an amount that could fill all the other Great Lakes plus three additional Lake Eries. With an average depth approaching 500 feet, Superior also is the coldest and deepest (1,332 feet) of the Great Lakes. The lake stretches approximately 350 miles from west to east, and 160 miles north to south, with a shoreline almost 2,800 miles long.

All those numbers usually add up to a very cold swim.

Well, remarkably, the water was perfectly comfortable, and we had as delightful a swim as one could ever want in the clear waters of Superior. The surface water temperature was around 68°, though it was a certainly nippier as one got a little deeper.

So, it’s a good time to paddle or swim along the shores of Lake Superior! For an array of data on Lake Superior, go to www.coastwatch.msu.edu/twosuperiors.html

Celestial Events

            On 8/25, look before dawn for Mars about 3° north of the waning crescent moon. The new moon occurs on 8/28. On 8/31, look for Saturn about 7° north of the waxing crescent moon.

            I’m sure you’ve noticed how late the sun is now rising and how early it’s setting, but if not, we’re down to less than 13 ½ hours of daylight as of 8/28 – autumn is on its way.

           

NWA 8/5/11

A Northwoods Almanac for August 5 – 18, 2011

Black Flies and Loons

In an average year, over 50% of nest attempts by loons fail, but since loons will nest up to three times in a given year, they are often successful in subsequent attempts. Nest predation is usually the leading cause of nest failure, with raccoons leading the pack as the most common predator. But other species also predate on the eggs, including red fox, mink, raven, and bald eagles. Other causes of nest failure include 1) flooding of nests due to water level changes or wave action, 2) abandonment due to black flies, 3) repeated human disturbance resulting in nest abandonment, and 4) failure of eggs to hatch.

This spring, however, nest failure reached what may be an all-time high due mostly to a huge black fly hatch. In particular, one black fly species, Simulium annulus, feeds primarily on the blood of common loons. During warm springs, black fly swarms peak in mid to late May in northern Wisconsin, coinciding with the peak of loon nest initiation, and often cause nest abandonment. This spring, a much higher percentage of loons’ first nest attempts failed throughout our area, with black flies serving as the major cause of failure. The precise numbers on this, however, are still being calculated and won’t by available until late September.

The good news is that most of the loons re-nested, and by that time the black flies had subsided enough that most of those nests were successful. Getting the eggs to hatch is the key in loon reproduction because once chicks hatch approximately 85% survive to fly off the nest lake in the fall.

Wild loons can live 20-25 years, thus they also have numerous nesting seasons to attempt to produce young. So, one bad spring is not cause for great alarm, but nevertheless is worrisome.

Sightings

Dragonflies: Beth Huizenga took an excellent picture of a female calico pennant dragonfly in early July at the Wolter wilderness area. She felt it was one of the prettier dragonflies she has seen, and I’d agree. A few days before Beth sent us her photo, Mary and I had paddled on Camp Lake and had seen many dozens of these small dragonflies alighting on emergent vegetation along the shoreline. The males’ scarlet

abdominal spots make them very distinctive, while the female differs by having yellow abdominal spots.

Albino Crows and Squirrels:

Linda Thomas reported that there are two white (presumably albino) crows on the Plum Lake golf course, apparently the young of two black crows that are seen with them.

I also received two reports of albino squirrels, one from Ron Morrell and another from Mara Coon. Mara sent a photo of the one she had seen on Broken Bow Lake.

So how rare is albinism? Over 300 species of North American birds and animals, from whales to snails, have been recorded as having some form of albinism or its many variants. In humans, about one in 20,000 people have one type or another of albinism. Mammalogists estimate that one in 10,000 wild mammal births results in a true albino. In birds, one study of 30,000 wild birds captured in mist nets in Southern California found only 17 displaying some degree of albinism, or one in 1,764 birds.

Triplet Loon Chicks:

             Suzy Foster sent me a photo of triplet common loon chicks on McCullough Lake. Triplets are very rare – one to two chicks are the absolute norm.

            Bobcat: Jim Schumaker sent me an exceptional photo of a bobcat walking through their back yard near Sayner several weeks ago. Bobcats are usually secretive and seldom seen – this one clearly hadn’t heard about this expectation.

Kingbird Dilemma and Fix

Eastern kingbirds often nest right along shorelines, and are known to use boat lifts and docks as nesting sites. Their choice of these nest sites can be a major problem given that kingbirds are “kings” of their nesting territory and do not tolerate intrusions, human or otherwise.

So, here’s how to handle this dilemma as experienced by Dave Eitel near Minocqua: “On June 29, a pair of kingbirds had built a nest in one of the cup holders on the pontoon boat and there were three chicks in it. Big problem. If we used the boat the birds wouldn't get fed, and not using the boat was out of the question.

“The solution: move the nest. I rigged up a plastic milk case with a heavy brick in it so it wouldn't blow away, and set that on a bench on the pier near the boat. I then used a beach umbrella to disguise my dastardly deed from the birds and snatched the nest from the boat and put it on the pier about 8 feet from the original next location. The birds couldn't find it (just kept flying to the spot where it had been), so I moved the crate back to the boat about 2 feet from the original location. After about an hour the birds finally found it and started feeding the chicks again. A couple of hours later I moved the crate to the pier and they found it after about a half hour. 

“The next morning I moved the nest in its crate on the bench 20 feet or so at a time, ultimately placing it on top of the boathouse where there is plenty of open space and lots of perching areas and the kingbirds are feeding away. It was amazing how long it took them to go back to the nest each time it was moved, but it got shorter after a while. One final move to the farthest corner of the roof and the birds are happy and we're happy. About 11 days later the chicks had flown the nest and were sitting nearby in the trees as the adults continued to feed them.”

Red-necked Grebe

Pat Schwai sent me a photo of a red-necked grebe swimming near the shoreline and over a projecting snag. She noted: “Occasionally it dove but remained in the same area even when we approached it to take photos. As dusk was falling we became concerned that it might be tangled in fishing line. Fortunately it was free and had left the area by morning (7/22).”

She asked that I not reveal the site because of the rarity of the bird. And indeed seeing a red-necked grebe in our area is a rarity. Because they are at the edge of their geographic range in Wisconsin, they are listed as a state endangered species. They typically breed in more northern and western areas from Alaska to Thunder Bay, Ontario. I’ve never seen one here, though I have seen numbers of them in migration on Lake Superior at Whitefish Point Bird Observatory near Paradise, Michigan. Their rusty red throat is absolutely beautiful.

Northern Water Snakes

Several weeks ago, Mary and led a paddle trip on the Trout River, and we stopped at a beaver dam to look for basking northern water snakes. We hit the jackpot and observed eight of them, all of which acted quite unperturbed by our excited peering.            Our only true water snake in northern Wisconsin, these two to three foot-long, non-venomous snakes blend in very well with the beavers’ wooden dams given their brown and tan coloration. They mostly eat frogs, crayfish, minnows, and slow-moving small fish, so pose no significant ecological problems, and instead often make a positive impact on a fishing lake by thinning our stunted fish.

Deer flies and more deer flies and more . . .

So, how ‘bout them deer flies this summer! Yikes. Between the mosquitoes and the deer and horse flies, it’s been a tough summer to be in the woods. I like to use the commercially made sticky patches on the back of my hat to catch deer flies, and on one recent hike, I captured 42 of the little beasties in less than an hour. A participant on the hike had another 32 on his patch, so between us we had 74 deer flies (see www.deerflypatches.com to order). More importantly, the circling deerfly Indianapolis 500 racetrack that was going on around our heads came to a very thankful close.

It’s the bloodthirsty females that exact the pain. Unlike mosquitoes, deer flies and horse flies are “stealth” fliers that circle their target before landing from behind and usually at the highest point, and then biting immediately. The females use their knife-like mandibles to cut through human flesh, leaving a cross-shaped incision. The good news is that compared to that of mosquitoes, the deer fly season is intense but relatively short.

Horse flies are the 747s of the family. E. Laurence Palmer, in his Fieldbook of Natural History, describes the horse fly mouthparts as “a series of cutting and piercing stylets that can penetrate the toughest hide.” Their bites often bleed, because the female’s saliva contains an anti-coagulant. The black horse fly can be 1¼ inches long but looks and feels much bigger.

Horse flies and deer flies have the charming habit of pursuing cars and bicycles. My bicycle solution is to tie a helium balloon to the back of your bike. Since deer flies and horse flies like to fly around the highest thing, let them spend their time biting your balloon. Better yet, put some sticky solution like Tanglefoot on the balloon, and you’ll trap dozens.

Celestial Events

            August 6^th marks the average midpoint between ice-out and ice-up on our area lakes, while August 7^th marks the midway between summer solstice and autumn equinox.

            The Perseid meteor shower peaks on 8/13, but you can begin looking for it as early as August 8^th. Unfortunately, the full moon occurs on the 13^th as well and will illuminate the sky too much for prime viewing.

NWA 7/15/11

A Northwoods Almanac for July 15-28, 2011

Aquatic Flowers

            Mid-July typically marks the beginning of spectacular aquatic wildflower displays that last well into August. A number of aquatic flowers have already come and gone, but it’s now that our lakes and rivers reach their height of flowering diversity and abundance. A shallow lake clothed in water lilies and pickerelweed simply soothes the soul. We could eliminate a lot of societal stress if folks would slowly paddle a canoe along the shoreline of one of our lakes rimmed in full flowerful regalia.

            Trying to learn all the flowers can take time, so if I had to recommend five to be sure to know, my list would include these most common and showy flowers: white water lily, pickerelweed, blue flag iris, marsh milkweed, and Joe-pye weed. I’ve included pictures of a few of them, but if you want to learn your aquatic and shoreline plants, here are the best resources for our region:

Through the Looking Glass by Borman, Korth, and Temte

Aquatic Plants of Wisconsin by Skawinski

Wetland Plants and Plant Communities of Minnesota and Wisconsin by the US Army Corps of Engineers

A Great Lakes Wetland Flora by Chadde

           

Sightings – Red-Headed Woodpeckers

Lisa DeHorn has had a red headed woodpecker visiting her suet feeders in Hazelhurst since Memorial Day weekend.  She notes, “I've not seen one on our property before nor up in the Minocqua area in the last 14 years of visiting regularly. I'm wondering if this is a fluke or if we may be honored with their presence regularly in the future. Used to see them a lot in Adams county in my youth, but they've become a rare sight. The hairy woodpeckers are not happy about the new visitor/resident.” 

             Lisa also has had red-bellied woodpeckers nesting over the last three years on her 10 acres. Here’s how she describes her property: “Our 10 acres is a very mixed forest of pine, oak, maple with aspen and birch phasing out. We don't cut the understory back so the birds have hazelnut and viburnums. Our property abuts a 97-acre parcel that is also managed very naturally with plenty of snags.”

Because of their management approach, the DeHorn’s have seven species of woodpeckers utilizing their woodlands: pileateds, hairies, downies, yellow-bellied sapsuckers, red-bellied woodpeckers, northern flickers, and now the red-headed woodpeckers.

A last note on why red-headed woodpeckers have become so uncommon, this from Wisconsin’s All-Bird Conservation Plan: “This species is in decline over its entire range. There has been a 50-55% decline nationwide, and approximately 60-70% in Wisconsin. The most recent Breeding Bird Survey data corroborate these findings, indicating significant declines range-wide and within Wisconsin.

“Loss of snags, fire suppression, firewood harvest, ecological succession of open woodlands to closed-canopy woodlands, and vehicle-caused mortality are all significant issues, as is interference competition with the European Starling. Invasive shrubs, such as buckthorn, may degrade existing habitat and also pose a threat to Red-headed Woodpeckers.”  

Swimmer’s Itch

            Mary, Callie, Mary’s sister Nancy, and I all took a lovely swim in the Manitowish Chain of Lakes on a very hot July 1, and an hour later we were itching like crazy with “swimmer’s itch,” the first time (and hopefully the last time) any of us have ever gotten this malady.

Technically known as schistosome dermatitis, swimmer’s itch appears as red itching, bite-like welts. The organism that causes swimmer’s itch is an immature life stage of a microscopic flatworm. Its complicated life history begins as an adult in the blood of infected ducks, geese, gulls, swans, muskrats, beavers, and other water-based organisms. The flatworm produces eggs that are eventually passed through the feces of the animal. If the eggs land on water, they release small, free-swimming larvae that search out certain species of aquatic snails. The infected snails eventually release a more developed form of the larvae, which then swim in search of a bird or mammal so they can start their lifecycle over again.

            The problem arises for humans when the microscopic larvae mistake us for the appropriate bird or host mammal, burrow into our skin, and cause an allergic reaction and rash. The good news is that they die quickly because they can’t develop inside a human. The bad news is that the leave inflamed welts that cause a lot of itching for nearly a week.

            Since the larvae are most common in shallow water by shorelines, prevention options exist. Given that the organism starts out most commonly in the stomach lining of ducks, if you are currently feeding waterfowl, stop!

And if ducks like to loaf on your dock, try to move them on. These actions will not only reduce the chances of the parasites being released in your swim area, they will also help keep the waterfowl wild, rather than semi-domesticated, which is worthwhile in itself.

            A second strategy is to swim in deeper water away from shore where you’re less likely to come into contact with the shoreline-loving flatworms.

            The third strategy is to immediately dry off or take a shower after getting out of the water, which helps prevent the larvae from finding refuge on your skin. They only burrow in once the water starts to dry on your skin.

            Only about one-third of the human population is apparently sensitive to the infection, so your family or neighbors may not be bothered one bit, while you may be a very unhappy camper. Swimmer’s itch isn’t contagious, so can’t be spread from one person to another.

Please note that the presence of ducks and/or snails does not mean that the flatworms are present! Some of the clearest recreational waters in the state experience swimmer’s itch annually, whereas other lakes may have an occasional outbreak or none at all. Wind and currents may also carry the larvae up to four miles from the release area.                        So, before any of us panic and go out and try to eliminate every snail we see, please recall that snails are beneficial organisms that feed by scraping algae off of rocks, sand, and plant stems, thus helping to clean water. And snails are also eaten by a host of organisms, including many fish species that folks work awfully hard to catch.

Currently, 58 species of snails live in the waters of the Great Lakes region, and swimmer’s itch is really quite uncommon. In the scheme of things, swimmer’s itch is little more than a nuisance to humans, and by taking proper precautions, most folks will never even encounter it.

Celestial Events

            The full moon occurs tonight, July 15.

The warmest days of a Northwoods year occur between July 17 and August 2nd, with an average high of 80° and a low of 57°. July 24 is statistically the hottest day of the year in the U.S., and presumably in the Northwoods as well. Lake temperatures typically reach their highest in the last week of July – Lake Katherine in Hazelhurst reaches it’s warmest average temperature, 76°, on July 25 and 26, according to Woody Hagge’s 38 years of data.

Poisoned Eagles Treated and Released

On June 1, seven bald eagles were released back in the wild nearly two months after they had ingested a deadly poison at an Eagle River landfill. Marge Gibson and her staff at Antigo’s Raptor Education Group treated the eagles non-stop after they had rescued them on April 9. The eagles had been accidentally poisoned in what is the largest documented mass poisoning event of its type in U.S. history. Initially there were eight eagles at the site, but one flew away and was later found dead.

Unfortunately, details of the poisoning cannot be released because the case remains under Federal investigation.

The Raptor Education Group does exceptional work, as evidenced by this event. See their website at www.raptoreducationgroup.org for how to visit their facility or to donate to their efforts.

Black Terns

            A small colony of black terns has again nested on Powell Marsh, and is easily seen by walking out on the dike at the main overlook to the “T” intersection. The birds are noisy and not in the least afraid of humans, so they often fly back and forth right overhead.

Historically, black terns were widespread in Wisconsin and regarded as a common breeding species. Today, they are concentrated in east-central, southcentral, and southeastern Wisconsin, and their population shows a long-term decline. One reason for their decline is the simple loss of wetlands. Prior to Euro-American settlement, wetlands occupied an estimated ten million acres of the total 35 million acres of Wisconsin’s land area. Today, only 53% of these wetland habitats remain.

Their decline may also be due to human disturbance, reproductive failure due to predation, adverse weather or water level fluctuations, and loss of winter and migratory habitat, so there’s no smoking gun. Because of their decline, black terns are listed as a species of Special Concern species in Wisconsin.