A Northwoods Almanac for August 23 – September 5, 2013
Hummers Beginning Migration
Late August marks the beginning of migration for ruby-throated hummingbirds. Many people have contacted me recently saying that large numbers of hummers are congregating at their feeders and “tanking up” for their push south. Male hummers precede the females in both the spring and fall migrations, while the juveniles of both sexes lag behind the departure of the adult females in the fall. Telling an adult female from a juvenile is very difficult, so most of us won’t know which is leaving, but the last to go, usually around mid-September, will almost certainly be a juvenile. Some males, on the other hand, may leave as early as the end of July.
The juveniles do not follow or fly with an adult. They find their own way, a perilous journey of a thousand miles or more into Central America, landing somewhere between Mexico and Panama. According to banding studies, most don’t survive to return the following year.
Their migration appears to take place after the passage of a strong cold front followed by a northwest wind, a tailwind, which makes obvious good sense for a bird that weighs only 1/10th of an ounce. Migration takes place overland during the day, and most migrants are seen during the midday hours, a likely indicator that the birds must “refuel” in the early morning hours before undertaking a long flight.
Before migration, hummingbirds feed heavily and often, doubling their weight and gaining fat to fuel the journey. Their overland migration is nearly synchronous with the peak flowering of jewelweed (Impatiens capensis), indicating that this flower is a very important nectar source and may influence the timing of migration.
To go from Wisconsin down to the Gulf Coast of the United States takes 3 to 5 days, assuming no stopover vacations for the hummer. To fly the 500-mile-distance across Gulf of Mexico takes another 18 hours if the weather is good, or 24 hours if the weather is unkind, so add another day. And then it takes another couple of days to reach its winter home in Central America. So, with no intervening rest stops, it would take a Wisconsin hummer a little less than a week to reach its wintering grounds. In reality, however, it usually takes about 2 weeks, since hummers spend time along the way feeding, resting, and waiting for good weather. Some choose to not cross the Gulf, but instead follow the coastline of the Gulf of Mexico, a decision made by individual birds for reasons that remain a mystery.
Remarkably, although the ruby-throated hummingbird is widespread and much-loved, many fundamental aspects of its migration and breeding ecology remain poorly understood.
Leave your hummingbird feeders up into early October, or at least two weeks after you see the last hummingbird – migrants may still be coming through.
And if you see a hummer riding on the back of a Canada goose, call me. I have a good optician to recommend for you.
Loon Study on Turtle Flambeau Flowage
In the most recent Journal of the Wisconsin Society of Ornithology, “The Passenger Pigeon,” local researchers Jeff Wilson, Terry Daulton, and Bruce Bacon published the results of their 2012 study of loon nests on the Turtle Flambeau Flowage (TFF). The TFF contains over 150 islands and has around 175 miles of shoreline, only 5% of which is developed. Annually, the TFF supports from 22 to 32 nesting loon pairs, in addition to many non-breeding loons who interact with the breeding pairs.
The researchers wanted to identify and quantify the causes of nest failures in loons. So they placed digital infrared motion detection cameras above 21 nests to determine what, if anything, was causing nest losses. Prior to this study, raccoons have largely been blamed, as have mink and otters, as well as gulls, crows, eagles, and disturbances by people. But no study had actual proof of who were the culprits, and this study’s use of cameras was hoped to be one way to offer some incontrovertible truth.
The cameras were placed on a ten-foot high pole above the nests and pointed directly down at the nests for the entire 28-day incubation period. All were set to take 1 picture every 30 seconds whenever movement at the nest trigged the shutter. Date, time, and temperature were all imprinted onto each image.
On the 21 camera monitored nests, 7 successfully hatched eggs (33%), 4 were washed out by wave action and high water (19%), and 3 (14%)were destroyed by predators. Two of the predators were clearly raccoons and the third was a mink.
Of the other 7 nests, two were suspected of predation but the camera failed to capture the culprit. Three nests were abandoned. At one nest, the adult loon accidently rolled its egg into the water after one egg had been removed by an unknown predator the previous night. And the final nest had infertile eggs.
An additional 18 nests were monitored visually via binoculars/scope. Five of those successfully hatched eggs (28%), 5 were washed out, 4 had unknown failures, 2 were destroyed by unknown predators, 1 was infertile, and one failed due to people camping too close to the nest.
Combined, the 39 nests surveyed had 12 successful hatches, a 31% success rate, while 9 were washed out (23%), and 6 were destroyed by predators (15%).
This rather low success rate is not cause for great concern given that loons are long-lived, often to 20 years or more, and thus don’t need high annual replacement rates.
Interestingly, northern populations of common loons did not evolve with raccoons, which are only a relatively recent addition to the Northwoods following land clearing and development. Raccoons were actually stocked in northern Wisconsin in the 1940s from the Poynette Game Farm.
Loon productivity varies dynamically from year to year. In 2011, over 50% of first nest attempts by loons in Vilas, Oneida, Forest, Langlade, Price, and Iron counties were lost due to nest abandonment caused by swarms of black flies. Second nest attempts, however, proved mostly successful, and productivity was deemed adequate.
In 2012, no nests were abandoned due to black flies. Instead, nest flooding and predation were the principle known causes. That spring was unusual in how early the ice went off our lakes. On the TFF, which is controlled by a dam, the Flowage wasn’t completely refilled until around June 1. Given that the first loon nest was initiated on May 8, that meant that water levels kept rising for another 3 weeks, in many instances flooding out the nests, which on average are only built 6 inches above the water surface.
The research cameras recorded wave action washing out nests as the water rose, as well as loons unsuccessfully adding nesting material to try to raise their nests above the water.
One management recommendation arising from the research is for water stabilization on flowages to occur by May 1 so loons have a fair chance at placing their nests at the right height above the water. It may be that stable water levels are every bit as important as other factors in loon nesting success.
Sightings – Coming Soon
Nighthawks have begun their migration. Look for flocks of them in the early evening darting around in the air, mouths wide open, in search of insects. Peak migration occurs in late August as they follow the last hatches of insects south.
Powell Marsh Master Plan
The DNR is resuming the master plan process for the approximately 4,800-acre Powell Marsh Wildlife Area in Vilas County. The wildlife area lies three miles south of Manitowish Waters, and is bounded by the NHAL State Forest and by the Lac du Flambeau Indian Reservation on the south. A public information meeting will be held on August 24 from 2-5 p.m. at the Manitowish Waters Community Center, with a short presentation at 3 p.m.
The updated planning documents, including maps of the property, can be viewed by searching for “master planning” on the DNR website – dnr.wi.gov – and clicking on “Powell Marsh Wildlife Area.” The planning materials area also available at the DNR Woodruff Service Center, or by contacting Michele Woodford at 715-356-5211, ext. 207, or email: Michele.Woodford@Wisconsin.gov.
Currently, Powell Marsh Wildlife Area is mostly an open peatland with several small flowages and small lakes. It encompasses a portion of a 20,000 acre wetland complex mostly owned and managed by the Lac du Flambeau Band of Lake Superior Chippewa.
August brings a lovely array of roadside wildflowers into being, though many of them are not native to North America. Some of these aliens are not invasive, and thus not of concern – butter and eggs, for instance, or goat’s-beard, mullein, common St. John’s-wort (though some say this is invasive), and tall buttercup.
Other non-natives are invasive, however, and need to be removed. The list is long, but the ones that I think are of most concern, at least of the upland flowers, are spotted knapweed, tansy, bird’s-foot trefoil, most thistles, curly dock, common burdock, and orange hawkweed. Garlic mustard is the one I fear the most – if you haven’t seen what it’s done in southern Wisconsin, you have no idea how extraordinarily invasive this species can be.
Some roadside species that one might think to be non-natives turn out to be natives, like stinging nettle, goldenrods, ragweed, fireweed, and common yarrow.
Thoreau had an interesting take on “weeds,” writing: “I sympathize with weeds perhaps more than with the crop they choke. They express so much vigor. They are the truer crop which the earth willingly bears.”
Others simply say that weeds are plants that out of place.
Regardless, enjoy the roadside displays – our first hard frost may not be that far away.
As of 8/28, we’re down to 13.5 hours of daylight. By 9/6, we’ll be at 13 hours, well on our way to equal day and night on 9/22, the autumn equinox.
On 8/31, look before dawn for Jupiter about 4 degrees north of the waning crescent moon.
For planet watching in September, brilliant Venus is very low in the southwest at dusk, as is Saturn. Before dawn, look for both Mars and Jupiter in the east.