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Thriving kestrels get study's attention

by: COURTESY OF STACIE STRUBLE  - Kelsey Brown holds a kestrel captured for tagging in the countryside near Forest Grove.Editor’s note: This article was written for Pacific magazine, the student publication of Pacific University in Forest Grove, and is republished here courtesy of the magazine.

There are mice in the car, two of them.

Quiet little rodents in a shared cage, sipping at a water bottle and running on a red exercise wheel.

Little do they know, they are bait on this early July morning. 

They ride in the back seat of an ultra-quiet hybrid Ford Escape with me and Pacific University senior Kelsey Brown. Senior Nikk Novero rides shotgun, while Environmental Studies Professor Rich Van Buskirk steers us down a rural gravel road.

Less than a mile from the university’s Forest Grove campus, we’re in the heart of Oregon farmland. Houses sit nestled in small groves of trees, separated by acres of crops. To the east are rows of berries; to the west, recently cut hay fields. The horizon is broken by small stands of old-growth forest.

All of that makes this prime habitat for the American kestrel, a once-plentiful small falcon seen throughout the continent. The birds, Van Buskirk explains, are one of the smallest raptor species, measuring about the size of a robin. A favorite of farmers, these “sparrowhawks” feed on mice and voles in the fields.

Despite their popularity with human landowners, their numbers have been on the decline for several decades — except in the countryside just outside Forest Grove.

Kestrel populations here are thriving. Bird pairs near Pacific University are hatching as many as five young in a season, while in Sherwood, not 20 miles away as the, well, kestrel flies, a good year means a brood of one or two young.

Van Buskirk and the two undergraduate research students working with him want to know why.

“What about this landscape is successful?” Van Buskirk asks. “When you work with endangered species, it’s hard to identify what’s missing, what’s caused the population collapse. If we can see what works here, we might explain the decline elsewhere.”

The bait works

Just minutes into the drive, Brown raises a pair of binoculars and points out a kestrel perched on a nearby powerline. Van Buskirk stops the car, and we stare for a few moments before Brown pulls a trap from the back.

It’s called a bal-chatri, a common means of catching falcons. But, as with all the equipment they use, Van Buskirk and his team have had to modify the design for the kestrels, which are much smaller than their hawk and eagle cousins. This one is a metal bicycle wheel with a cage fastened in the center. The outside of the cage is covered with fishing line nooses.

Brown opens a small hatch and sets a mouse inside. Van Buskirk creeps from the driver’s seat to lay the trap in some brush off the road.

We back up to give the bird some space, but she’s not shy. She immediately swoops down, intent on a mousy snack. On her fourth dive, she’s caught in one of the snares but quickly escapes. Surprisingly, she keeps trying.

by: COURTESY OF STACIE STRUBLE  - Pacific University Professor Rich Van Buskirk gives instructions as Kelsey Brown examines a hooded kestrel captured in the countryside near Forest Grove. “She’s more cautious than the first time, but she keeps coming back in,” Van Buskirk observes. “These mice are just too much of a draw. They can’t resist.”

It takes a few more tries, a different trap, and a site several yards up the road, but it’s a lucky day. We have a bird within 30 minutes. 

The kestrel is gently removed from the trap while a blanket is spread on the roadside berm, and the process of weighing, measuring and tagging begins. (The mouse is returned to its cage in the car, hopefully no worse for the experience.)

A falconer’s hood covers the bird’s eyes and a soft jacket wraps its wings. It seems docile, but when the hood slips, the bird almost bolts.

Van Buskirk catches it in his hands, “like a ninja!” Brown says.

“We’re lucky this is a young bird,” the professor replies. “An adult would have been gone. They just kind of wait for that moment when the person who has them isn’t quite paying attention.”

It takes 35 minutes for the team to finish tagging the bird with a radio transmitter. Like the traps, the radio transmitters had to be modified for the small birds. A falcon can only carry about 3 percent of its body weight unnoticed, meaning this 119-gram bird’s transmitter has to weigh no more than a penny. The team has experimented with different transmitters and different ways to attach them, and today’s method is a leg-loop harness that allows the radio to lay unobtrusively on the bird’s lower back. The loops are made of Teflon catheter tubing, which won’t chafe or cut the bird, and the kestrel will shed the whole unit within a year.

First tagging, then monitoring

The kestrel spreads her tail feathers for a moment, showing off brown-red plumage, then takes flight. Brown and Novero watch her through spotting scopes, then grab handheld antennae and radio transmitters to try to pick up her signal.

Tagging the birds is exciting, but it’s only the beginning of the project. Researchers now will spend hours tracking the birds’ activity, documenting the vegetation in various sectors of land, and mapping all the data on computers back at Pacific.

The information will be added to Van Buskirk’s ongoing research, which will require years of data. This is his fourth year studying kestrels, with different undergraduate students each summer. The ongoing study is supported in part by a grant from the M.J. Murdock Charitable Trust.

While Brown and Novero won’t be present for the final outcome of the long-term research, they stand to gain from the experience.

Both will develop senior projects from the summer of research. Brown has been looking at kestrel nesting sites. Kestrels are cavity dwellers, often building their nests inside abandoned woodpecker holes. She has been examining nest sites in ash and oak groves to identify the conditions that seem to work best. Novero is interested in the land characteristics that appear to contribute to nesting success, and is running a toxicity study on addled or defective eggs to see how the mother bird’s diet might impact breeding success.

Kestrels, Van Buskirk says, give students solid wildlife tracking experience they might not have in relation to a study of bigger animals. Even in the falcon world, hawks and eagles are more dangerous and require more field experience before handling. (An eagle’s beak, for instance, can sever a human finger.) High-profile projects, such as local work with extremely endangered condors, takes years of experience.

Novero and Brown say the fieldwork has given them insight for the future. Novero hopes to work outdoors, perhaps with Oregon Fish & Wildlife or the U.S. Forest Service, while Brown dreams of becoming a primatologist.

Both hope to conduct more research and get field experience before exploring graduate school to pursue their scientific careers.

Jenni Luckett is editor of the Pacific University magazine, Pacific, where this story originally appeared.