A Northwoods Almanac
for 10/1 – 14, 2015
Bird Migration!
Bird migration has peaked, though
many birds will keep coming through until snowfall. On 9/1, Hawk Ridge in
Duluth experienced an enormous migration of 91,667 non-raptors, representing
one of the highest counts ever recorded in Duluth. The count included some
spectacular numbers: 28,054 common nighthawks (third highest count in MN),
12,842 cedar waxwings (new MN high count), and 33,758 warblers, of which 19
species were identified. I have a hard time identifying fall warblers when
they’re sitting in a nearby tree, so identifying them in flight boggles me!
The best raptor flight of the
autumn occurred on 9/19 – 17,704, of which 16,815 were broad-winged hawks.
The songbird “super flight”
continued on 9/22 with 20,793 non-raptor migrants, including 4,532 American
robins, 2,595 blue jays, 1,868 yellow-rumped warblers, and 1,144 white-throated
sparrows.
Perhaps more impressively, that
same day they had an afternoon flight of at least 1,358 dragonflies, although the
counters noted that it could easily have been 2,000 to 3,000. Most were
meadowhawks along with common green darners. The counters noted that “waves of
meadowhawks moved through that were difficult to count, as there were also many
raptors and other birds to keep track of, too.”
There’s precious little actually
known about dragonfly migration, so where all theses meadowhawks and green
darners are actually headed is unclear.
Pileated Holes –
Square or Round?
Back in the spring, Mary Lou Fisher
in Lac du Flambeau sent me several photos of a tree on which a pileated
woodpecker had chiseled out perfectly rectangular holes. Other holes on the
tree, however, were oval, and Mary Lou wondered if there was any significance
to the differently shaped holes.
Well, I’ve researched this every
which way I can, and I haven’t been able to find any information linking the
shape of the holes to a particular function. I’ve seen some evidence that nest
holes are typically oval, while foraging holes are often rectangular, but
nothing definitive. If the grain of the tree is very straight, that may encourage
excavations with precise 90° corners, but the same tree may have both round and
rectangular holes, and even occasionally triangular holes. Perhaps some
woodpeckers are simply more geometrically challenged, or more creative as the
case may be, than others.
What is clear about pileateds is
their role as a keystone species. A keystone species is an organism whose
influence on the ecosystem is disproportionately large compared to its
abundance or biomass. Pileateds are crucial to many forest ecosystems. Their
excavations are used as nesting sites and roosting shelters by a diverse array
of birds and mammals, particularly the larger secondary cavity users like
boreal owls, wood ducks, and American martens. Many other species dine on
insects in their cavities, too, including hairy, downy, and red-bellied
woodpeckers, northern flickers, and sapsuckers, as well as house wrens.
In an Alberta study, 54% of 878
inspected pileated woodpecker cavities had evidence of at least one secondary
cavity user. In another study, black-throated green warblers were found on
three occasions nesting in pileated woodpecker feeding cavities in Ontario, a
very surprising finding!
In her book To Whom the
Wilderness Speaks, Louise de Kiriline Lawrence wrote about a 70-year-old
aspen tree that in the last four years of its life hosted six species of cavity
nesters including pileateds, hooded mergansers, red-breasted nuthatches, wood
ducks, American kestrels, and northern flickers, all of which made use of
pileated-drilled holes. So, pileateds act as condo developers throughout many
forests.
Ants remain their favorite food,
especially carpenter ants. George Sutton, Pennsylvania’s state ornithologist
back in the late 1920s, reported finding 469 carpenter ants in the stomach of a
male pileated.
“Pileated” means “crested,” which
comes from their species’ name – pileatus – first bestowed on them by
Carl Linnaeus, the Swedish taxonomist, back in the late eighteenth century.
Pronounce “pileated” with a long “I” or a short “i”; it doesn’t matter. What
does matter is their creation of living spaces for so many other creatures, and
their importance as a control of wood-dwelling ants and beetle larvae.
Goshawk Update
You may
recall the story I wrote in my last column about the goshawk that was rescued
and taken to the Northwoods Wildlife Center for rehabilitation. I got an update
from Amanda Walsh at the NWC on 9/28 – the bird is recuperating well. She’s
eating, gaining weight, and getting feisty. However, she still has no vision
out of her left eye, and they discovered a break in her wing last week that
required the insertion of a pin. So, the bird is still unable to fly, but Amanda
is optimistic that she will do so when the wing is healed.
Nevertheless, given the bird’s lack
of vision, it’s unlikely that it can be released. That’s the bad news; the good
news is that it will most likely become an “education” bird that will be kept at
the Center. However, the bird’s story is still unfolding – I’ll keep you
updated.
Sightings – Merlin,
Flickers, Red Admiral Butterfly, White-throated Sparrows, Yellow-rumped
Warblers
Jim Swartout sent me a photo of a
male merlin along with this note: “I recently entered my boathouse and
encounterd a sea of feather. Several pairs of barn swallows nest in there.
Although they are messy, I leave them alone as I feel their mosquito predation
is beneficial. I heard flapping and encountered a small hawk that had pinned
itself against the window trying to escape after his successful hunt. I used a
mesh bag to subdue and quiet it. After a quick once over, and a couple of quick
pics, I released it, and it flew quickly and effortlessly away.”
Northern flickers are being
commonly seen now along the edges of highways, busily feeding on ants. If you
kick up a bird as you’re driving about the size of a robin that has a white
rump, it’s almost certainly a flicker. Flickers used to be divided into
yellow-shafted and red-shafted flickers, but these are now considered
sub-species. Flickers in eastern North America are mostly the yellow-shafted
form. They’re migrating now – their peak migration is from late September to
early October – but they don’t necessarily go all that far, wintering from
southern Wisconsin south into Florida. Where “our” flickers go is uncertain,
but the literature suggests that the bulk of them winter in the Gulf Coast
states.
Beth Huizenga in Presque Isle sent
me a photo of a red admiral butterfly sipping sugar water from her hummingbird
feeder on 9/20. Red admirals migrate, so perhaps, like hummers, this one was
stoking up for the flight south.
Numerous white-throated sparrows
have been foraging in our yard for over two weeks. One usually thinks of sparrows
as seed-eaters, as indeed they are, but these sparrows have been eating
literally all of our elderberries, nannyberries, dogwood berries, and
maple-leaved viburnum berries.
And today, 9/28, we’ve had a flock,
or flocks, of yellow-rumped warblers foraging throughout our yard all day long.
I watched one glean the underside of a dogwood twig, eating what looked to me
like small bumps all along the twig. I wonder if it was eating the scale
insects that have been so prevalent this summer! If yellow-rumps do indeed eat
scale insects, they should be able to fatten up to unprecedented levels because
these insects are so widespread this year.
Witch Hazel
We planted a witch hazel in our
yard over a decade ago, and it’s flowering now, perhaps taking the title for
the latest flowering shrub in the North Country. Why it flowers so late is
unclear, but some researchers believe that the
plant's late flowering period induces insects to pay special attention to it
since the flowers are the only game in town. Even though there usually have
been numerous frosts by this late date, some small gnats and bees inevitably
survive and are rewarded for their pollinating labors with nectar and sticky
pollen.
Clusters
of small, pale yellow blooms, each with four streamer-like petals, hug the
twigs, the flowers often lingering into November. Oddly, each individual
witch-hazel blossom is equipped with both sets of reproductive organs, but each
acts as either a male (producing pollen only) or female (producing fruit only),
eliminating any chance of self-fertilization. Once
pollinated, actual fertilization doesn’t occur until the following spring. When
the fruits are ripe in the fall, they burst open and shoot out two smooth black
seeds a distance of up to 33 feet. Then the seeds need two winters of dormancy
in the soil before they’ll germinate.
Traditionally,
branches of witch hazel were
used as "divining rods" to locate underground sources of water.
Mary’s father could “witch” for water, and he helped us locate our first well
when we moved to Manitowish 31 years ago. He used a forked alder branch, and it
was amazing to watch that wood pull hard toward the ground when he walked
across our well site.
Witch
hazel is found mostly in the lower two-thirds of the state, and only occasionally
occurs in northern counties.
Celestial Events
The
Draconid meteor shower peaks after sunset on 10/8. Before dawn on 10/10, get
the trifecta – look for Venus, Mars and Jupiter above the moon.
