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.
Sightings
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!
Other Sightings
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.
Eagle Hoax
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.”
