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Sax-Zim Bog project helping solve the kestrel conundrum

Conservation efforts hope to stem the decline of the Northland's smallest falcon.

A kestrel just before being released across from its nesting box, seen in the background. Contributed / Friends of the Sax-Zim Bog

Most American kestrels are winging their way south for winter now, heading from the fields and meadows of Minnesota and Canada down to warmer climes.

Exactly where the little falcons go, however, has remained a mystery.

“We know some go farther south and some only go as far as they have to go to find rodents and snakes all winter, maybe southern Minnesota or Iowa in a warm winter,” said Clint Dexter-Neinhaus, head naturalist for Friends of the Sax-Zim Bog.

But a project that started this summer might help shed more light on kestrels, a species that has been declining nationally for the past half-century, again for reasons not fully understood. Bird experts with the Minnesota Department of Natural Resources and other groups fitted 22 Minnesota kestrels with radio transmitters that are picked up by a series of small radio towers set up specifically to track birds.

Twelve of those birds were from the Sax-Zim Bog area northwest of Duluth where local raptor researchers, the Friends of the Sax-Zim Bog and citizen scientist volunteers have been working for six years to restore kestrels on the open landscape around the bog.


And one of those radio-wearing kestrels already has revealed some fascinating facts.

Kestrel migration.jpg
Gary Meader / gmeader@duluthnews.com

Kestrel No. 33676 was detected from three different towers in just a few days in September, traveling at least as far as Neosho in southwestern Missouri, 716 miles south of the Sax-Zim Bog. And she did nearly half of that — flying between a tower at the St. Croix Valley Nature Center near Hastings, Minnesota, to a tower 334 miles away near Grantsville, Missouri — in a single day.

“Already, something we wouldn’t have expected,” Dexter-Nienhaus noted.

The radio transmitter and antenna are visible on this adult kestrel in the Sax-Zim Bog north of Duluth. Contributed / Friends of the Sax-Zim Bog

Kestrel box bonanza

Kestrels like open areas in which to hunt their prey, small critters and insects mostly, but they build their nests in tree cavities. In order to help them out a bit near the bog, Frank Nicoletti, banding director for Hawk Ridge Bird Observatory, put up the first 14 kestrel boxes in 2016. He’s added more every year with the help of the Friends group.


“I just saw how steep their decline was in some areas and thought we should give it a try here,” Nicoletti said. “Where I grew up back East, there are no more kestrel nesting pairs at all.”

The boxes look like wood duck houses (which helped restore that species), but instead of being placed in or near wetlands, they are placed in upland areas close to open meadows, bogs and fields. Each box is on a separate pole about 10-12 feet above ground.

An American kestrel. Contributed / Quarry Hill Nature Center

“We just make sure they aren't too close to any farm buildings where starlings group up or the starlings will take over the nest box and push the kestrels out,” Dexter-Nienhaus said. The boxes are placed out of sight from each other, but the kestrels so far haven't been too territorial.

As of this summer, the sixth year of the kestrel nest box project, there were 49 usable nest boxes on the landscape in and around the bog. A record 23 of those were used by nesting pairs of kestrels.

“I figured if I built it, they would come. And they sure have,” Nicoletti said.


Clinton Dexter-Nienhaus, head naturalist for the Friends of the Sax-Zim Bog, installs a kestrel nest box in an open area of the bog. There are now about 50 kestrel boxes in place in the area in the sixth year of the American kestrel project. Contributed / Friends of the Sax-Zim Bog

Mary Gabrys of Duluth was one of 14 volunteers monitoring the nest boxes across the bog this spring for Friends of the Sax-Zim Bog. They used a GoPro camera on a long stick to see exactly when each box full of eggs hatched so researchers could climb up and band the chicks. (The adult kestrels, when sitting on eggs, generally won’t try to fly away when researchers open the box lid to grab and band them, making the job unusually easy.)

“It’s been really interesting watching them use the boxes. When it started it was just sort of to see if they would use them. … Now it’s gone way beyond that,” said Gabrys.

The antenna from the radio transmitter fitted onto this adult American kestrel in the Sax-Zim Bog is seen against the colorful tail feathers of the bird. Contributed / Friends of the Sax-Zim Bog

A veteran birder at the bog, Gabrys said it feels good to help a species that’s been in decline. The boxes have produced an impressive 270 chicks over six seasons that have fledged — survived to fly out of the box — of which 254 have been banded so they can be tracked to help study the species. And now a dozen adults are wearing solar-powered radio transmitters, too, that should keep beeping for three or more years.

The transmitters will help track the birds’ movements in and around the bog, what type of habitat they need in summer, in addition to their migration flights and wintering areas.

This summer 76 eggs were laid producing 67 chicks for an average of 4.4 eggs per nest and 3.9 chicks per nest, slightly fewer than average. Six boxes had total nest failures this summer, the most in the six years of the project, possibly due to extreme temperature fluctuations in early summer, Nicoletti said.

Bugs for breakfast

This year’s heat and drought might have impacted kestrel nest success, but it definitely impacted their diet. The dry weather made for a major hatch of grasshoppers which became a larger-than-usual portion of the kestrel's meals in and around the bog.

“There were a couple of boxes that were absolutely full of uneaten grasshopper legs and wings, where in a typical box we may see only a handful of grasshopper parts,” Dexter-Nienhaus reported.

The nest box effort isn’t only aimed at studying kestrels. It’s also aimed at helping restore the species that has declined by an estimated 51% between 1966 and 2017 across the country, according to the North American Breeding Bird Survey. Kestrels are listed as endangered or threatened in four northeastern states, and 21 states list them as a species of concern. The Minnesota Breeding Bird Atlas lists it as a species of moderate conservation concern here.

Efforts to help kestrels recover have been stymied since scientists don’t know what’s causing the decline or where it’s happening — on breeding grounds to the north, along the migration routes, on their wintering grounds in the south or maybe all of the above. Experts say habitat loss, declining food sources, fewer nesting spots, exposure to pes­ticides, climate change and increased predation by hawks all could be factors.

An American kestrel. Contributed / Quarry Hill Nature Center

One study found a widespread phenomenon of kestrels getting smaller in recent years, both in weight and wing size, but it’s unclear why.

“Frank knew this area would support kestrels, but maybe they just needed a little help here,” Dexter-Nienhaus said. “This is a species that’s seen significant decline across the country for 50 years, although the decline has been a little slower in Minnesota the last decade or so. They are hanging on here.”

Dexter-Nienhaus said the kestrel project will now focus on keeping at least 50 next boxes available for kestrels when they return to the bog in April. More kestrel boxes are going up near Duluth, too, as Nicoletti spreads his efforts to see just where these birds will nest if given the chance.

“I’m going to try to get 75 more boxes up later this winter, early next spring … some in the bog, some north of Duluth and maybe some in Northwestern Wisconsin,” Nicoletti said. “I think we can keep expanding it. I don’t think we know yet what the limitations are for habitat up here. That’s one thing we are going to find out.”

John Myers reports on the outdoors, environment and natural resources for the Duluth News Tribune. He can be reached at jmyers@duluthnews.com.

An American kestrel. Contributed / Quarry Hill Nature Center

Get involved

For more information on the Kestrel Project in the Northland go to the Friends of the Sax-Zim Bog website saxzim.org.

Nationally, the American Kestrel Partnership is keeping track of conservation efforts. Go to kestrel.peregrinefund.org .

If you have property with broad, open areas and would like to put up a kestrel box, contact Frank Nicoletti at fnicoletti@hawkridge.org.

About kestrels

North America’s littlest falcon — roughly the size of a blue jay or mourning dove — the American kestrel packs a predator’s fierce intensity into its small body. They have slender, pointed wings and long tails typical for falcons. They are about 9 inches long from beak to tail tip, and their wingspan is about 22 inches. Adults weigh an average of 4.1 oz.

Kestrels are among the most colorful of all raptors: The male’s slate-blue head and wings contrast elegantly with his rusty-red back and tail; the female has the same warm reddish hue on her wings, back and tail.

Hunting for insects and other small prey in open territory, kestrels perch on wires or poles, or hover facing into the wind, flapping and adjusting their long tails to stay in place.

In flight, the wings are often bent and the wingtips swept back. American kestrels usually snatch their victims from the ground, though some catch quarry on the wing. They are gracefully buoyant in flight, and are small enough to get tossed around in the wind. When perched, kestrels often pump their tails as if they are trying to balance.

American kestrels occupy habitats ranging from deserts and grasslands to alpine meadows. Despite their fierce hunting abilities for small prey, Kestrels sometimes end up as prey for larger birds such as northern goshawks, red-tailed hawks, barn owls, crows and sharp-shinned and cooper’s hawks, as well as rat snakes, corn snakes and even fire ants in the South.

Kestrels are declining in parts of their range and you can help them by putting up nest boxes in open areas.

Sources: Cornell Lab of Ornithology; American Kestrel Partnership

John Myers reports on the outdoors, natural resources and the environment for the Duluth News Tribune. You can reach him at jmyers@duluthnews.com.
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