A Northwoods Almanac for October 28 – November 10, 2011
Robin Migration Update
In my last column, I reported that on 10/4/11, counters on Hawk Ridge in Duluth tallied 9,050 migrating American robins flying south over the ridge.
Well, that was nothing.
On 10/9, an astonishing 39,127 robins flew over the ridge, followed the next day by another 10,329!
Why so many? I think it’s a reflection of the remarkable adaptive capabilities of robins and their subsequent nesting success in virtually every known habitat in North America. We’re simply awash in robins.
A major reason is that robins rear usually two and sometimes three broods a season. One study modeled on breeding data from Madison, WI, took a hypothetical robin population of 1,000 pairs, and found 147 pairs, or 15%, would successfully raise three broods, 621, or 62%, would raise two broods, 191, or 19%, would raise 1 brood, and 41, or 4%, would fail to breed successfully.
Robins usually lay 3 to 4 eggs per clutch, though how many of those survive to become fledglings varies widely. Using field data to model a hypothetical robin population, one researcher estimated the rate of survival of young from hatching through November 1 to be only 25%. Even so, by then more first-year birds were estimated to be in the population than adults.
Robins can live a long life, too – one banded wild bird lived 13 years and 11 months – though average life expectancy of robins, and most songbirds, is typically only a few years. Within six years, one can usually expect a complete turnover in a population of songbirds.
Crows Now Migrating in Large Numbers
Migrating robin numbers peaked two weeks ago, and have dropped in the last week. Now, migrating crow numbers are peaking, but in considerably smaller numbers. On 10/18, the counters observed 1,825 crows migrating over Hawk Ridge; on 10/19, 1,182 crows; and on 10/20, they tallied 3,232 crows crossing the ridge.
Crows, like blue jays, are hard to figure out when it comes to migration. Some migrate, some don’t, and why there is such variability is unclear. In one study, half of 49 crows banded in winter between 38° and 43°N latitudes in the Eastern U.S. were permanent residents. In other studies, individuals banded in Alberta, Saskatchewan, and Manitoba migrated southeastward through Montana, N. Dakota, and western Wisconsin as far as Oklahoma and Texas. In yet other studies, some wintering crows in Illinois were found to come from Michigan, Wisconsin, and Ontario.
When we’ve done our Christmas bird counts in Manitowish Waters in the last decade, we have had good numbers of crows, but whether they are resident birds staying for the winter or migrants which have come down from further north is completely unknown. Prior to our milder winters, crows were seldom present in our counts.
Crows weren’t always a major component of our landscape. Considered rare in Wisconsin prior to 1855, crows became common in the southern part of the state by 1875, and were considered abundant by 1890, as more and more land was cleared.
Abandoned Bald-faced Hornet’s Nests
A reader recently e-mailed this: “We have a magnificent wasp nest hanging from our garage on the back of our house. It’s at least a foot in diameter and more than that deep. It’s really a work of art. Dare I saw it off the overhang and explore its innards? Do you know what happens to the wasps in the winter? Do they just die, in or outside the hive? Could they be awakened by our messing with the nest?”
All good questions. So, here’s the scoop as best as I understand it: Near the end of summer, the bald-faced hornet queen (bald-faced hornets belong to the genus of wasps called yellowjackets) lays eggs. After pupation, these fertile males and females will mate. As winter approaches, the hornets die – except any just-fertilized females. These hibernate underground, under logs or in hollow trees until spring. The nest is abandoned, and will not be reused.
As to when it’s safe to take a nest down, once we’ve had hard frosts in the autumn, it’s very unlikely that any hornets will still be present. However, discretion being the better part of valor, I think some lengthy observation should be entertained until it’s clear that no hornetss are coming or going.
I should add that old hornet nests are good winter shelter for other insects and spiders, and that birds will tear them apart, looking for food. So, leaving the nests up for the birds is perhaps the best practice.
A River of Birds
Gloria Johnson from Woodruff sent me this on 10/19: “My husband and I are driving on I80 in Nebraska on our way to Phoenix. Last evening at dusk we witnessed at least a 5-mile by approximately 20-yard-wide formation of birds. It almost looked like a ribbon. They were flying just above tree top level. We couldn't ID them but I'd say they were between a junco and robin in size. I've never seen anything like it. We were traveling west. They were flying east quite close to the highway. Do you think they were looking for a place to land? As my husband commented, they were flying with purpose!”
I suspect this was a roosting flock of blackbirds, which can reach several million birds. Each morning the roosts spread out, traveling as far as 50 miles to feed, then re-forming at night. Roosts peak in number of birds in September. In fall, some birds continue in late-summer roosts, some in roosts of migrating transients, and some in winter roosts.
I’ve never seen this phenomenon, but there are many videos online – here’s one: www.youtube.com/watch?v=8jr64WSzkTo&feature=related
Celestial Events
Planets in November: At dusk, look for brilliant Venus and Mercury both very low in the southwest, and setting soon after dark. Jupiter is also very bright at dusk, but is found in the southeast and then rising high in the south as the evening progresses.
At dawn, look for Mars high in the south and for Saturn very low in the southeast.
On 11/1, look for Mercury about two degrees south of Venus at dusk. On 11/3, we’re officially down to 10 hours of daylight. 11/7 marks the midway point between autumn equinox and winter solstice. Full moon occurs on 11/10 – the “Beaver/Freezing/Ice is Forming/Snow” moon – depending on what tribe one references.
Sightings
Mary and I saw our first migrating fox sparrow on 10/17, and our first migratory flocks of snow buntings on 10/19.
I’ve never birded on Pelican Lake in Oneida County, but it sounds like I sure should, because on 10/21 at 1 p.m., a birder reported seeing the following from the pullout along Hwy 45/47 on the south side of the lake: 12 white-winged scoters, 7 surf scoters, 1 long-tailed duck, 54 horned grebes, 14 pied-billed grebes, 110 scaup, 20 redheaded ducks, 21 common loons, 16 common goldeneyes, and 1 common merganser.
Tamarack: Autumn’s Last Canvas
After the multi-hued maple leaves have drifted down, and then the yellow aspen and birch leaves scatter, autumn delivers one last splash of color that trumps all those – tamarack’s gold. Perhaps tamarack delivers such breathtaking colors because it comes last, standing mostly alone among the skeletal trunks and branches of the deciduous trees that await the first snow. Or perhaps tamarack’s gold pops so brilliantly because the trees are often illumined by slants and shafts of sunlight escaping from the frequent gray overcasts of late October. Or maybe tamarack offers such stunning moments because so few people are now around and the world is clearly shifting into the seasonal Armageddon we call winter where any color becomes a rarity on a white canvas. November brings out much that is bittersweet, and tamarack is the last antidote to it before the cold settles hard into our bones.
Tamarack needles are falling with every wind now, and the golden branches will soon turn threadbare, fulfilling November’s riches to rags story. Good news in the botanical world is called May, and it’s a long ways off. The last tamarack needle dropped may be the best definition we have of when winter truly starts.
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