You’ve probably seen Idaho’s smallest raptor — the American kestrel — perched on telephone poles, eyeing an unsuspecting mouse or lizard.
With a hooked beak, talons and sharp eyesight, this tiny carnivorous bird sits at the top of the food chain. But mysteriously, the kestrel population has been in decline for decades.
Idaho scientists are leading the charge to find out why.
This year marks the 30th anniversary of Treasure Valley’s kestrel nest box project, one of the longest running kestrel monitoring programs in the U.S.
Since 1992, researchers have been putting up wooden nest boxes across Treasure Valley — most are in Kuna, Meridian, and south of Boise.
Kestrels, who like to nest in crevices, lay eggs and raise their young in these man-made homes from early spring through late summer. Scientists and Boise State University students monitor the boxes and collect data, adding to decades of observations.
“That kind of time series gives you really incredible insights on how kestrel populations work,” said Julie Heath, who runs the program. Heath is a biological sciences professor at Boise State University.
For example, kestrels might be adapting to climate change and warmer Treasure Valley winters by nesting earlier, Heath said.
While birds used to lay eggs in the middle of April, they now lay them as early as March. Some birds that nest early actually raise two rounds of young, Heath said.
Kestrels are responding to us, too. Despite being a “human tolerant” species, the birds have their limits — in areas with lots of people, kestrels have higher stress hormones and are more likely to abandon their nests, Heath explained.
Nevertheless, “We think the populations here are doing pretty good,” Heath said.
The Treasure Valley kestrels are considered a healthy group, Heath added, and researchers have been comparing Idaho’s birds to places in the country where boxes aren’t filling up as much.
While kestrels may not be too keen on humans, humans have a unique interest in kestrels.
Many avian enthusiasts in the Treasure Valley build their own nest boxes, and some have sponsored boxes through a collaboration between Boise State University and The American Kestrel Partnership, a project of The Peregrine Fund.
The “adopt-a-box” program gives people an inside look at the lives of kestrels as they start laying their eggs and growing up, said Matthew Danihel, engagement coordinator for The Peregrine Fund.
The program also helps support the Treasure Valley kestrel monitoring project, as long-term research projects are difficult to fund, Danihel added.
Brian Roche, a birdwatcher based in Oregon, adopts a box in Treasure Valley for himself, his parents, and his brother each year.
“I just think they’re neat birds,” Roche said.
Roche notes that kestrels are easy to observe — as “opportunistic” birds, they nest closer to humans. He has a kestrel box at his home, which has housed around twenty birds since he built it in 2014.
He likes seeing the birds go from eggs in his nest box to adults flying overhead.
And he’s not the only one — this year, a record high of 62 boxes were adopted in the Treasure Valley, bringing the total number of adoptions to 150 since the program started in 2015.
Roche and his family plan to keep adopting boxes each season. He’s also working on his own box, which has been outfitted with advanced monitoring technology over the years.
Putting up a kestrel box is “really easy” and doesn’t require much monitoring, Roche said. If people have the landscape, structures, or ability to better nature, they should consider doing it, he added.
More information about installing or sponsoring a box can be found at The Peregrine Fund’s website here.