Most American kestrels are flying south for the winter now, moving from the fields and prairies of Minnesota and Canada to warmer climates.
The exact destination of the little hawks, however, remains a mystery.
“We know some go further south and others only go as far as they have to go to find rodents and snakes all winter, maybe southern Minnesota or Iowa by warm weather, “said Clint Dexter-Neinhaus, chief naturalist for Friends of the Sax. -Zim Bog.
But a project that started this summer could help shed light on kestrels, a species in decline nationwide over the past half-century, again for reasons not well understood. Bird experts from the Minnesota Department of Natural Resources and other groups have fitted 22 Minnesota kestrels with radio transmitters that are picked up by a series of small radio towers specially designed to track birds.
Twelve of these birds were from the Sax-Zim Bog area northwest of Duluth, where local raptor researchers, Friends of the Sax-Zim Bog and volunteer citizen scientists have worked for six years to restore kestrels in the open landscape around the bog.
And one of those radio-carrying kestrels has already revealed some fascinating facts.
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 334-mile tower near Grantsville, Missouri – in a single day.
“Already something we weren’t expecting,” Dexter-Nienhaus noted.
Boon kestrel box
Kestrels like open areas to hunt their prey, mainly small critters and insects, but they build their nests in tree cavities. To help them out a bit around the bog, Frank Nicoletti, Banding Director for Hawk Ridge Bird Observatory, installed the first 14 boxes of kestrels in 2016. He adds new ones 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,” said Nicoletti. “Where I grew up in the East, there are no kestrels nesting pairs at all.”
The boxes look like wood duck houses (which have helped restore this species), but instead of being placed in or near wetlands, they are placed in upland areas near open grasslands, bogs and fields. Each box is on a separate post about 10 to 12 feet above the ground.
“We just make sure that they aren’t too close to the farm buildings where the starlings congregate or the starlings will grab the nest box and repel the kestrels,” Dexter-Nienhaus said. The boxes are placed out of sight of each other, but the kestrels so far haven’t been too territorial.
As of this summer, the sixth year of the Kestrel nesting box project, there were 49 usable nesting boxes in the landscape in and around the bog. A record 23 of these were used by breeding pairs of kestrels.
“I thought if I built it they would come. And they definitely did,” said Nicoletti.
Mary Gabrys of Duluth was one of 14 volunteers surveying 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 and band the chicks. (Adult kestrels, when sitting on eggs, typically don’t try to fly away when researchers open the lid of the box to grab and band them, making the job exceptionally easy.)
“It was really interesting to see them using the boxes. When it all started, it was just to see if they would use them.… Now it’s gone way beyond that,” Gabrys said.
A seasoned bog bird watcher Gabrys said it was nice to help a declining species. The boxes produced a staggering 270 chicks in six seasons that took flight – survived to fly out of the box – of which 254 were banded so they could be tracked to help study the species. And now, a dozen adults are also wearing solar-powered radio transmitters, which are expected to continue ringing for three or more years.
The transmitters will help track the movements of birds in and around the bog, what type of habitat they need in the summer, in addition to their migratory flights and wintering grounds.
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 less than the average. Six nesting boxes experienced total nesting failures this summer, the highest number in the project’s six years, possibly due to extreme temperature fluctuations in early summer, Nicoletti said.
Insects for breakfast
The heat and drought this year may have had an impact on the success of the kestrels’ nests, but it certainly impacted their diet. The dry weather resulted in a large outbreak of grasshoppers which became a larger portion of the kestrel’s meals in and around the bog than usual.
“There were a few boxes that were absolutely full of uneaten grasshopper legs and wings, where in a typical box we can only see a handful of grasshopper parts,” Dexter-Nienhaus reported.
The nest box effort isn’t just about studying kestrels. It also aims to help restore the species which declined by about 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 consider them a species of special concern. The Atlas of the Breeding Birds of Minnesota lists it here as a species of moderate conservation concern.
Efforts to help kestrels recover have been hampered as scientists do not know what is causing the decline or where it is occurring – on breeding grounds to the north, along migration routes, on their wintering grounds in the south or maybe all of the above. Experts say habitat loss, dwindling food sources, shrinking nesting sites, exposure to pesticides, climate change and increased predation by hawks could all be factors.
One study found a widespread phenomenon of kestrels becoming smaller in recent years, both in weight and wing size, but it’s unclear why.
“Frank knew this area would put up with kestrels, but maybe they just needed a little help here,” Dexter-Nienhaus said. “This is a species that has seen significant decline across the country for the past 50 years, although the decline has been a bit slower in Minnesota over the past decade. They hang on here.”
Dexter-Nienhaus said the kestrel project will now focus on keeping at least the next 50 boxes available for the kestrels when they return to the bog in April. More and more boxes of kestrels are growing near Duluth, as Nicoletti scrambles to see exactly where these birds will nest if given the chance.
“I’m going to try to get 75 more boxes later this winter, early next spring… some in the bog, some north of Duluth and maybe some in northwestern Wisconsin,” said Nicoletti. “I think we can continue to expand it. I don’t think we know yet what the habitat limits are here. That’s something we’ll find out.”
To be involved
For more information on the Kestrel Project in Northland, visit the Sax-Zim Bog Friends website at saxzim.org.
Nationally, the American Kestrel Partnership tracks conservation efforts. Go to kestrel.peregrinefund.org.
If you have a property with large open spaces and would like to install a kestrel box, contact Frank Nicoletti at [email protected]
North America’s smallest falcon – roughly the size of a blue jay or grieving dove – the American Kestrel packs the fierce intensity of a predator into its tiny body. They have thin, pointed wings and long tails typical of falcons. They are about 9 inches long from beak to tip of tail 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 rust-red back and tail; the female has the same warm reddish tint on her wings, back and tail.
Hunting for insects and other small prey in open territory, kestrels perch on wires or poles, or soar into the wind, flapping and adjusting their long tails to stay in place.
In flight, the wings are often folded and the wing tips are folded back. American kestrels typically tear their victims to the ground, although some catch prey on the fly. They float gracefully in flight and are small enough to be tossed about in the wind. When perched, kestrels often pump their tails as if trying to balance themselves.
American kestrels occupy habitats ranging from deserts and grasslands to alpine meadows. Despite their fierce hunting abilities for small prey, kestrels sometimes end up becoming prey for larger birds such as northern wood pigeons, red-tailed hawks, barn owls, crows and sharp-tibia hawks and cooper, as well as rat snakes, corn snakes and even fire ants in the south.
Kestrels are in decline in parts of their range and you can help them by setting up nesting boxes in open areas.
Sources: Cornell Ornithology Laboratory; American Kestrel Partnership
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