A Northwoods Almanac for January 25 – Feb. 7, 2013
Diet of Sharp-shinned and Cooper’s Hawk
A sharp-shinned hawk visited our feeders over the weekend, joining the Cooper’s hawk that has been a regular at our feeders all winter. We’re delighted, but the songbirds must surely take a dimmer view of their presence because the winter diet of both hawks consists mostly of songbirds.
How do we know when to look for the hawks? Whenever we hear a songbird hit our windows, or if all the birds suddenly scatter frantically in a dozen directions, or if some suddenly freeze and don’t move for 15 seconds or more, then a hawk (or shrike) is usually nearby.
So, due to their predation, I’ve wondered what the maximum daily attrition rate is for the songbirds at our feeders. It’s this: On average, a sharpie weighs in at 5 ounces (dove-sized), while a Cooper’s hawk weighs in at 15 ounces (crow-sized). One account of Cooper's hawks says they eat 28% of their body weight per day, and 87% of their diet consists of eating other birds. So, they eat around 4.2 ounces a day. And if 87% of that menu is birds, that’s about 3.6 ounces of bird.
An average chickadee, redpoll, or goldfinch weighs in at about 0.5 ounces, so that’s 7 of the little guys a day, though only a few of those may be at our feeders. However, if the Cooper’s would take a mourning dove, which weigh 4 ounces each, they would only need one of those a day. Or if they consumed one of the many blue jays (at 3 oz. each) that gobble our birdseed so voraciously every day, they could possibly get by with just one of those per day.
For the sharpies, at one-third the weight of the Cooper’s, their consumption (assuming the same 28% of body weight daily) would be around two songbirds a day.
Some folks try to scare the hawks off their property, angered by their predation, something they often witness through their windows at lunch while eating a chicken or turkey sandwich and watching their feeders. I must admit I am conflicted when observing predation – I’m thrilled to see the successful predator and sorrowful for the prey. I know that’s the way of it all, a way that preserves a general balance of populations, which keeps this complex Earth ticking. I’m always honored to be able to observe it, and thus I hope the hawks stay, and I wish the songbirds great vigilance.
Speaking of predation, on a snowy hike last week near Springstead, we came across a pile of ruffed grouse feathers from a very recent kill. Nothing terribly unusual there – ruffed grouse are a desired prey species of many predators. What was unusual, however, was the pile of fresh grouse buds lying on top of the feathers. This grouse must have just finished filling its belly with buds when the predator killed it, ate everything but the grouse’s feathers and the buds, and then departed.
Since we could see no tracks in the snow near the kill, the predator must have been a hawk or owl. Northern goshawks are well known to predate upon grouse, but a great horned owl could also have taken the grouse, as could have a rough-legged or Cooper’s hawk.
It was the number and perfect shape of the buds, however, that most intrigued me. Grouse “bud” all winter long, often forming flocks of up to 10 birds and flying out to feed in the early morning. Each bird fills its crop with buds and twigs and then returns to its roost to digest its meal in safety. The birds typically go out foraging again in the afternoon before roosting for the evening. With full crops, they digest their food throughout the winter night, the digestive action increasing their metabolism and body heat to help keep them warm.
This grouse may have been roosting at night when taken by an owl, or foraging that morning when it was perhaps taken by a hawk. I’ll never know, but I now have a better idea how many buds a grouse can store in its crop!
Tom Nelson sent a wonderful photo of a bobcat taken from their deck in Arbor Vitae during the middle of the day.
Wil Conway sent a fine photo of a coyote framed by the trees in front of it.
How Cold Is COLD?
Our recent cold snap was indeed cold (-17° on 1/21), but was it Really Cold? One way to look at the degree of cold is by examining the 2012 USDA Plant Hardiness Zone Map, the standard by which gardeners and growers determine which plants are most likely to thrive at a location. Each zone represents the mean extreme minimum temperature for an area, calculated from the lowest daily minimum temperature recorded for each of the years from 1976–2005. This does not represent the coldest it has ever been or ever will be in an area, but it simply is the average of lowest winter temperatures for a given location for this 30-year time period.
Our zone in northern Wisconsin is now rated as “4a”, with our average minimum now between -30° and -35°, which is a warm-up from our previous zone 3 status which assumed a minimum average low of -40°.
So, while -17° the other day kept me happily inside for the most part, it was really not that cold, at least compared to what we have historically termed “cold” in Wisconsin’s Northwoods. The coldest Mary and I have experienced in our nearly 30 years of living here was a spell of seven days from 1/29 – 2/4, 1996, when we had 7 consecutive days of lows below -30°, of which five of those days were also below -40°, peaking at -50° on 2/3.
My records are incomplete, and I would be happy to be corrected, but I believe we’ve only hit -30° once since 1997, meaning our zone 4a status is really a relic of the calculations that are averaged from 1976 – 2005. We’re actually significantly warmer nowadays.
While that relative warmth feels very good indeed, its ecological repercussions are vast and important. For the best in-depth, truly scientific discussion of temperature changes in Wisconsin, please closely read the Wisconsin Initiative on Climate Change Impacts at http://www.wicci.wisc.edu/about.php. It contains the best statistical data and the best analysis of what is happening to our winters, and what the implications may be.
A recent online video of an eagle grabbing a baby is an absolute hoax, but it’s had some apparent repercussions. Since the video was released, the Raptor Education Group, a wildlife rehabilitation center near Antigo, has taken in four hawks and two bald eagles, all of which were shot. The six are at least twice as many as the center usually gets in one month. Apparently, the U.S. Fish and Wildlife Service has received similar reports from around the Midwest and the country, with shootings of bald and golden eagles estimated to have risen about 25 percent in the month since the video came out.
Here’s the bottom line: Eagles don’t capture children and carry them away. There’s no record of this every happening anywhere – period. There are many more legitimate reasons to be afraid for our children than this hoax.
The North Wind
Our youngest daughter, Callie, was recently asked to write a piece about winter, and when she showed it to me, I thought it was worth repeating here:
“A northern child, I grew up in long winters. I knew deep snow and piercing cold. Summers stayed for days; winters for months. At the time this lacked profundity: it was just the way it was.
Now, as our world warms, I’m beginning to understand what my winter childhood gave me. In a year of scant snow and schizophrenic temperatures – a year when the south gets more snow than my northern home – I long for a blizzard. I long to be buried in snow, to wake up to frost decorating the windows, to have the north be the north.
I know what you’re thinking. Long winters are long. There’s a good reason why most people live elsewhere. Indeed, in the same breath as they curse the unseasonable weather, northerners quickly add, “Not that I’m complaining,” as if winter is an angry god who needs to be appeased.
Once – not so long ago, really – people did see winter as a god. Humans were small; the elements vast and unconquerable. Among others, the ancient Greeks leave us memories of this other time, this more primal time.
The North Wind, Boreas, is the ancient harbinger of winter. Like most Greek deities, he tends toward rapacity and temper tantrums. I imagine him thundering out of the north, his beard scaled with icicles, his robe whitened by frost. In Mediterranean Athens, his breath would have chilled like the gust of wind on snow, redolent of Scythian campfires, whispering Sarmatian stories. He came armed, not with iron, but with cold, with sharpened icicles and raging blizzards.
Boreas and his wife Oreithyia had four children, among them a daughter, Khione. Khione became the goddess of snow. How fierce she must have been, with her snow-white hair and her cold, cold hands, her eyes the color of a clear winter sky.
Her eyes reflect a clarity in winter that comes in no other season. To find it, you must go out on a perfect day, when the sky is a clear dome, and stand deep in the snow. You must allow yourself to become silent. You will feel the sharpness of the cold against your face. You will hear the persistent calls of chickadees, the thumping of ice trapped on the frozen lakes. But beneath all this there is a quiet so deep and profound that it must be a sign of something greater. Something larger than ourselves. Call it god – call it Khione, if you like – call it the soul of our world.
You cannot find this, not so easily, in melting spring or busy summer. But in winter, when the trees are naked and the living world forced quiet, it is right there.
I’m afraid we’re losing this. I’m afraid that in time, it will be gone. Not only gone, forgotten. Our world is becoming too warm. We are talking too much. We don’t spend enough time being still.
We have to remember to be silent. Outside, cupped in the world’s hand.”