Chesterton Tribune

Who goes there? State Park naturalists band Sawwhet Owls

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How cute is that? A Northern Saw-whet Owl, caught in a mist net for banding near the Tremont Shelter at Indiana Dunes State Park (IDSP), perches on the head of IDSP Chief Interpretative Naturalist Brad Bumgardner. This fall the naturalists at IDSP inaugurated a Saw-whet banding operation—only the fourth in the state—to acquire data about the numbers and behavior of this notoriously reclusive owl. In fact Saw-whets are not as tame as the photo would suggest. Instead, Bumgardner says, their instinctive response to perceived danger is simply to freeze. A total of 19 Saw-whets were caught, measured, banded, and released this fall at IDSP.                                                              (Photo provided)

 

By KEVIN NEVERS

Think of it as a ghost, passing silently through Duneland’s forest fastnesses and deeps on cold clear nights in October and November on its way south to a winter roost.

It may as well be invisible, for it’s rarely seen. If it tarries here, as it sometimes does, it goes to ground in secret stands of evergreen, and if you’re optimistic enough to search for it—look for its whitewash on trees—take a compass and be prepared to get lost.

It’s the Northern Saw-whet Owl. For ornithologists it’s something of a mystery bird whose behavior, migratory patterns, and even numbers are largely unknown. For birders it’s a highly prized because so reclusive target species.

And, just for the record, it’s arguably the cutest bird in the world.

This fall the naturalists at Indiana Dunes State Park (IDSP) inaugurated a Saw-whet Owl banding operation, only the fourth such station in Indiana, in the hope of adding data to ornithologists’ slim store of information about the bird.

“It’s a bird we know so little about,” IDSP Chief Interpretive Naturalist Brad Bumgardner says. “We don’t know how far south they go, they’re such a secretive bird. We don’t know the ranges of their breeding and non-breeding grounds. And it wasn’t until we started banding them that we began to learn even a little about their habits and how many there are.”

Of the eight owls commonly or uncommonly seen in Indiana, the Saw-whet is by far the smallest, about the size of a fist. Around 95 percent of its diet is comprised of small mammals, usually Deer or White-footed Mouse. It doesn’t hoot but rather gives a series of short whistles and very occasionally a rasp like the sound of a saw being whetted. The field guides describe it as tame and easily approachable (once it’s been located) but in fact, Bumgardner says, the Saw-whet’s default response to danger is simply to freeze.

Until seven years ago, no one had any idea how many Saw-whets were migrating through Indiana in any given year. The entire birding community might stumble across only a handful or two in a season, with the presumption that most—scores more? hundreds more?—were ghosting through the state undetected.

In 2002, however, Ross Brittain established a Saw-whet banding station in Yellowwood State Forest near Bloomington and then in later years added two more stations with Jess Gwynn. And the data they collected proved startling: between ‘02 and 06’ 434 Saw-whets were banded, for an average of around 90 per year; then, in ‘07 alone, fully 447 were banded, more than in the five prior years combined.

Turns out, every four years the rodent population spikes, with a concomitant spike in the number of Saw-whet migrants. More owl food, more owls.

Here’s another fact gleaned from Brittain’s work: fully 80 percent of the owls caught are females. The presumption: over the winter the males stay close to the breeding grounds, protecting their territory, in the hope of hooking up with the same female next year.

And another: Saw-whets are short-range fliers. Most migrating birds will travel hundreds of miles a night. Saw-whets, only 20 to 30 miles.

IDSP

The setup at IDSP works like this. Once it’s dark Bumgardner and his team rig a series of three virtually invisible mist nets—30 feet long and 12 to 15 feet high—in a thickly understoried woodland near Tremont Shelter, then play a recording of a Saw-whet’s calling at 110 decibels. Every hour, sometimes into the early morning, they check the nets. A Saw-whet which lands in a net won’t be injured but Bumgardner needs to be vigilant and punctual anyway because a Barred Owl would cheerfully steal a meal if given the chance.

After catching a Saw-whet, the team measures it, sexes it (if possible), attaches an individually numbered identifying band to its leg, then releases it.

Unfortunately, after several weeks of late nights at Tremont Shelter, the banders at IDSP succeeded in catching only 19 Saw-whets: a disappointing number but nevertheless much higher than the six banded by Brittain downstate.

Why the drop from previous years?

Bumgardner attributes it largely to the weather: 19 of 31 days in October saw measurable rainfall, while early November was brightly moon-lit. Chances are, he suspects, a lot of Saw-whets haven’t even left their breeding grounds in Canada and Michigan yet. “It looks like a lot are being held up north, bottled up, waiting for clear weather.”

Still, Bumgardner has culled some intriguing data from those 19 owls (15 female, two male, and two unsexed).

For one thing, nearly all of the Saw-whets were caught before 10 p.m., leading Bumgardner to suppose that they had actually flown Lake Michigan the night before, had roosted somewhere in the park during the day, and were only just becoming active in the early evening.

More intriguingly, though, nearly every one of the Saw-whets was caught on a clear night with light winds, leading credence, Bumgardner says, to the theory that this particular species is a “celestial migrant,” which is to say that, like certain other birds, it uses the constellations to migrate. “They may orient themselves by star patterns, not as we know them, of course, but as they see them. And they tend not to fly on a given night if the star patterns are obscured by cloud cover.”

So rare is the Saw-whet, Bumgardner noted, that these 19 represent fully 25 percent of all Saw-whets ever reported along the lakefront, according to local birder Ken Brock’s voluminous database.

Bumgardner has not yet heard of one of the IDSP Saw-whets being caught elsewhere by another banding operation. But one of his 19 had been previously banded in Stevens Point, Wis., while another—a female—actually ended up in the banders’ nets at IDSP three times, the second and third time fully two weeks after it was first caught.

For the record, virtually every one of the 19 birds was officially adopted by a member of the public, who were invited to participate on several nights of the operation. For $25—which will go to support further banding operations—a person receives a detailed letter and certificate about the specific owl and will be notified whenever and wherever it’s netted again.

The operation is being partially funded by the Northwest Indiana Migratory Bird Association (NIMBA), and Bumgardner says that NIMBA is considering a spring banding operation as well, in mid-March through mid-April, to supplement the almost total lack of data on Saw-whets’ flight to their summer breeding grounds.

“For me the banding operation is a dream come true,” Bumgardner said. “I’ve grown up loving owls.”

 

Posted 12/4/2009