NWA 10/1/15

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.