A Northwoods Almanac for July 5 - 18 , 2024
Black-capped Chickadees Nesting in Bluebird Box
Jennifer Heitz on Irving Lake sent me this email on 6/25: “We had chickadees build a nest in our bluebird house. We so enjoyed watching them go in and out and sing their happy song near their nest! The babies fledged at least a week ago, so we decided to peek inside the box. What a beautiful nest! One little egg was pushed into the back corner.”
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| photo by Jennifer Heitz |
Lots of folks are surprised to learn that black-capped chickadees are cavity-nesters. In studies on chickadees in Ontario, cavities were found most often in white birch (50%) and aspen (14%), while in interior British Columbia, most nest cavities were found in aspen.
Why aspens and white birches? They’re soft wood. Chickadees aren’t blessed with a chisel-like beak, so they’re only able to dig a hole in a dying or dead tree where the wood is rotting, like a broken-off snag of aspen or birch. If they do nest in other trees with harder wood, the nests are usually associated with knot-holes or have been previously excavated by another species.
Both sexes participate in excavating the hole, but the inside nest is built exclusively by the female, who typically uses a coarse material like moss and then lines it with finer material like rabbit fur and deer hair. Perhaps brushed-out dog hair would work, too.
Chickadees occasionally use nest boxes, particularly if no dead birch or aspen trees are nearby, but they actually prefer artificial nest snags to nest boxes. They like fixer-uppers! I’ve seen plans for building a nest snag out of PVC pipe, but using a hollowed out wooden tube seems far more natural. One way or another, the use of both types of artificial nests increases if the cavity is filled with wood shavings – chickadee females apparently enjoy removing the shavings and sculping the nest cavity to their specifications.
The female does all the incubation – usually for 12 to 13 days – while the male brings back food when she’s on the eggs.
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| a black-capped chickadee egg, photo by Jennifer Heitz |
The chicks hatch naked with their eyes closed, and weigh all of one gram. Fifteen days later, they will weigh 10 to 12 grams (recall that an ounce is equal to 28 grams).
The young typically leave the nest when they’re about 16 days old, but they stay with the adults for another 3 to 4 weeks. The parents provide all of the food for the chicks initially, but within a week, the young are finding their own food.
The chicks waste no time dispersing once they’ve mastered feeding themselves. One day, the whole brood is with both parents; the next day, the young scatter and move some distance away.
It’s interesting to note that pair bonds between adults most often last for several years. Of 94 pairs studied over 10 years in Massachusetts, there were only 15 instances of divorce, while 79 pairs (84%) remained together. In another study in Ontario, of 49 pairs observed over 8 years, only 11 instances of divorce occurred, while 38 (78%) of the pairs remained intact. Compare that to our human divorce rates, and perhaps we could learn a lot about relationships from chickadees.
Sightings – A Rain of Pine Pollen Cones, Blue-bead Lilies, and Garden Valerian
*The male pine cones from our three native pines – jack, red, and white – were recently coming down like rain during some high winds. All of our pines produce separate male and female cones on the same tree, and are wind-pollinated, the yellow pollen often releasing on a windy day in great plumes and then covering our cars or floating on water until it eventually sinks into the sediments.
Once pollinated, the female cones of the white pine and red pine mature and shed seeds in the autumn of the second year, while the female cones of the jack pine mature in the second year, but remain closed for several years, or for decades, until extreme heat from a fire or weather melts the resin that seals up the cones and the seeds can be released.
*Mary and I hiked the Lost Creek Falls Trail in Bayfield County last week and were impressed by the many large clonal colonies of blue-bead lilies (Clintonia borealis). A creeping horizontal rhizome tends to produce dense colonies of blue-bead lilies, but the plants also produces a number of large, deep porcelain blue berries, thus the name “blue-bead lily.” If you’re tempted to eat the berries in August, don’t. They’re thought to be mildly poisonous to humans, though one gentleman has written to tell me that he successfully ate them, but they tasted very bitter. Other sources say the berries aren’t poisonous, but confirm their foul taste. The strikingly beautiful berries should be left to only our aesthetic tastes.
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| photo by John Bates |
*Later that day in Washburn, Mary and I hiked the lovely Washburn Lakefront Walking Trail, and here we were surprised by the proliferation of a very tall wildflower that we’d never seen before, but which was clearly invasive. It turned out to be garden valerian (Valeriana officinalis), a sweetly scented pink or white flowered plant that belongs in Europe and Asia, not here.
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| garden valerian |
The plant has been present in North America since at least 1890 and has likely benefited from repeated introductions because of its ancient use as an herbal medicine. Hippocrates prescribed it as a sleep aid, and the plant has since been used to treat ailments including insomnia, anxiety, depression, and headaches. During both World Wars, valerian was used in treating victims of what was then called shell shock, and is now known as post-traumatic stress disorder). Valerian remains a popular commodity today, with several million dollars generated each year in sales in the United States.
Nevertheless, it completely took over some open fields and trail edges in Washburn, and while beautiful, this appears to be a plant that we all need to kill on sight if it appears here.
Winter Severity Index – Last Winter Was the Lowest Recorded
Since the early 1970s, the WDNR has used a winter severity index (WSI) to indicate the intensity of each year’s winter. From December 1 through April 30, dozens of sites around the state record one point each day if the temperature is 0 degrees F or colder, and one point each day if the snow is 18 inches or deeper. At the end of the season, if the points total less than 50, it’s considered a mild winter; 50 to 79 is moderate; 80 to 99 is severe; and more than 100 is very severe.
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| county by county WSI 2023-24 |
The previous WSI low was 14 in the winter of 1986-87. But last winter, the WSI for northern Wisconsin averaged 10, the lowest on record in the 64-year data set.
For comparison, the winter of 2013-14 was the most severe on record with an average WSI of 143 at northern sites.
You may remember that two winters ago we had tons of snow, but you may not remember that the temperatures were comparatively mild. Thus, the WSI for 2022-23 was a moderate 69 – not that hard a winter, at least according to this index which was designed to indicate the impact of winter on wildlife, and in particular, deer.
I also find last winter’s WSI remarkable because the highest values in our northern counties was 12, while values in the southern counties were nearly identical – Richland and Vernon counties, for example, were 11. Thus, overall the entire state experienced a very similar non-winter.
The question for those in the deer hunting community who think our deer numbers are too low is how well this low WSI has translated into higher deer survival and reproduction. My take from a botanical perspective is that our overall deer population remains too high, so I’m concerned about diminished tree and wildflower seedling survival if there’s a population boom.
We’ll see what shakes out as the summer progresses.
Cotton-grass Poisoning Lemmings
I’ve observed over many decades the beauty of cotton-grasses (Eriophorum sp.) in boggy habitats around our area, but I never knew that they were a favorite food of lemmings in the Arctic, and that they can produce a poison that leads to the lemming’s legendary suicidal behavior. David Attenborough writes in The Private Life of Plants: A Natural History of Plant Behavior:
“The ability [of cotton-grasses] to produce poison may be the cause of one of the most celebrated, almost mythic, events in natural history – the mass suicide of the Norway lemming. These little hamster-like rodents of the Arctic tundra increase in numbers year after year until there is a population explosion, and then hordes of them are said to deliberately drown themselves.
“The cause of this extraordinary behavior may be the fact, recently discovered, that when lemmings start to feed on the cotton grass and sedges that are their main food, the plants begin to produce a poison which neutralizes the lemmings' digestive juices. If the grazing is light, the plants stop doing this after about 30 hours, but if it is intense, as it is when the lemming population reaches its climax, they do so continuously. The effect on the lemmings is not only that they cannot digest their meals. Because they cannot, their bodies produce more and more digestive fluids, draining their physical resources and bringing them even closer to starvation. As a consequence, the more they eat the hungrier they get, and when having stripped the surrounding tundra they reach the edge of the sea or a lake, they swim out into it, in a frenzied attempt to find some food somewhere that will sustain them.”
Celestial Events
For planet-watching in July, look low in the west-northwest after dusk for brilliant Venus. Before dawn, look in the east for Mars, high in the southeast for Jupiter, and in the south for Saturn.
Today, July 5, the Earth is the most distant from the sun that it will be at any time this year. It’s at “aphelion” at 94.5 million miles away. Back on January 2, the Earth was at perihelion, only 91.4 million miles away.
The new moon occurs tonight as well.
Our average warmest days of the year occur from July 8 to July 28 with an average high of 78° and a low of 55°. If you’re a lover of heat, enjoy it while you can.
Thought for the Week
“I would say that there exist a thousand unbreakable links between each of us and everything else . . . The farthest star and the mud at our feet are a family; and there is no decency or sense in honoring one thing, or a few things, and then closing the list. The pine tree, the leopard, the Platte River, and ourselves - we are at risk together, or we are on our way to a sustainable world together. We are each other's destiny.” – Mary Oliver
Please share your outdoor sightings and thoughts: e-mail me at johnbates2828@gmail.com, call 715-476-2828, snail-mail at 4245N State Highway 47, Mercer, WI, or see my blog at www.manitowishriver.blogspot.com
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