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In late autumn a male great horned owl sent his soft, deep hoots out from a stand of trees in Minnetonka. He'd been away for two months and was making it known that this was still his territory, after some strange and, to him, incomprehensible events.

The owl's journey started one dark night in mid-August as he swooped low over a school field, unaware of the soccer net ahead. The netting ensnared the owl, who thrashed around wildly, trying to free himself. A good Samaritan discovered the exhausted raptor the next morning, and got him to the Raptor Center at the University of Minnesota.

Several weeks of cage rest and treatment healed his soft tissue and eye injuries, but the owl had another problem: His tail feathers were in bad shape, some broken in his entanglement, some while he was recovering. These flight feathers are critical to his ability to brake and steer while hunting and landing.

The owl couldn't be released back to the wild with those damaged feathers, but in the normal course of things, he wouldn't molt new tail feathers until next summer or fall, a long time to keep a wild bird in a cage. Luckily, there's an age-old remedy for such situations — it comes from the practice of falconry and is called imping. Two veterinary technicians at the Raptor Center are skilled at this procedure, as much an art as it is science.

Basically, damaged feathers are pulled out and replaced with feathers from another, (almost invariably) deceased bird. Each replacement feather must be from the same species and same location on the bird's body. So, in this case, new feathers needed to have been harvested from a deceased great horned owl's tail and replaced in the exact same order.

The surgical tools aren't at all esoteric, merely bamboo skewers, nail trimmer, ruler and quick-fixing epoxy glue.

Jamie Clarke performed the imping procedure on the anesthetized owl, first clipping off each old feather near the owl's body. After carefully measuring to make sure the new feather was the same length, he used a small piece of bamboo to join the donor feather to the owl's old feather shaft. When Clarke was satisfied that each feather was the same length and alignment as the old one, he glued the new feathers into the old shafts.

"Feather extensions," Victoria Hall called them. The executive director of the Raptor Center noted that imping isn't painful to birds, since feathers are made of the same dead material as our hair and fingernails. Imping is a temporary solution, and when the next molting season rolls around, new feathers will push the imped feathers out.

"It's an art," Hall says, "and it allows us to get the birds out of here so much faster" than if they had to wait for a natural molt.

Where do replacement feathers come from? The Raptor Center, like many rehabilitation facilities, has a freezer full of sets of flight feathers from birds that were euthanized, held in a row by tape to maintain their position on a bird. (The freezer keeps them from being devoured by feather mites.) Before imping the owl, Clarke pulled a set of great horned owl tail feathers from this feather library.

In just under 20 minutes the owl was transformed, all 12 of its torn and bent tail feathers replaced with a handsome new set, and he was groggily looking around the surgery. In just over a week, he was released near where he was found, to rejoin his territory and possibly even a mate.

Vet tech Clarke said that the Raptor Center performs about 100 feather implants a year. Most, he added, "are done in the spring or the fall as we prepare birds for release during migration season." (Great horned owls aren't migratory, but each needs to get back on territory as quickly as possible, before another owl claims it.) In some cases, only a few feathers need replacing, while in others, like the great horned owl, more feathers are involved.

Clarke imped 16 birds in September, including great horned and barred owls, broad-winged hawks, merlins, a peregrine falcon, Cooper's hawks, a kestrel and a red-tailed hawk. In most cases the birds had suffered some kind of trauma, either being hit by a car, slamming into window glass or fighting with other raptors (eagles often fight each other).

"We like to send our patients out as good as new," Hall said, and imping is the final touch, ensuring that Raptor Center patients are once again masters of the sky.

St. Paul resident Val Cunningham, a member of the St. Paul Audubon Society, writes about nature for local, regional and national newspapers and magazines, and can be reached at valwrites@comcast.net.

Another great horned owl, admitted to the Raptor Center after being caught in a soccer net.
Another great horned owl, admitted to the Raptor Center after being caught in a soccer net.

Raptor Center

Soccer nets are hazards

Soccer nets are almost invisible to night-hunting owls as they hunt for small animals on the ground. Owls can become tangled in such nets and suffer feather breakage or even mortal injuries as they struggle to free themselves.

The Raptor Center treats around 20 birds entangled in ropes (including nets) each year, and the majority are great horned owls.

"Everyone can help these nighttime hunters by simply taking down nets as night, so they don't accidentally catch an owl," says Victoria Hall, executive director of the Raptor Center. And for nets that can't be moved, Hall asks that fans or players not eat near them, because this results in food crumbs that attract rodents and other animals — and then owls.

Imping has long history

Imping is closely associated with falconry and goes back hundreds, possibly even thousands of years. There's a reference to imping in Shakespeare's "Richard II" ("Imp out our country's broken wing") and while the process is fairly straightforward, great care must be taken: Replacement feathers must duplicate the feathers removed, especially in terms of orientation (feathers are subtly angled). An imped bird must be able to control its flight feathers to glide, dive, catch prey and avoid any predators. Of course, out in the wild, raptors and other birds often break or lose feathers, and if the damage isn't severe, they usually can get along until their next molt.