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Pittsburgh Zoo to reintroduce barn owls to city habitats

Monday, May 13, 2002

By Don Hopey, Post-Gazette Staff Writer

This is a very bad news day for the mice among us.

A mother barn owl and two, 2-week-old fledglings in the Moraine Fund's breeding program. (Andy Starnes, Post-Gazette)

And it's not an "it's your birthday!" kind of day for Pittsburgh's voles, rats and other rodents either, especially those in and around Highland Park.

That's because the Pittsburgh Zoo & PPG Aquarium will soon start reintroducing barn owls to the city, possibly releasing its first group by the end of the month.

Nesting boxes already are going up on five meadows within the zoo grounds and plans are to eventually release more than 50 of the stealthy, seldom seen or heard birds. Each can eat four to six mice or other rodents a night and can fly up to five miles in search of their furry, scurrying food.

"The barn owl is a great and beautiful bird that was originally part of nature's formula in the Pittsburgh region," said Mark Browning, the zookeeper leading the reintroduction program. "This is a great way to bring the owl back into the county and also establish a natural rodent control around the zoo, where such populations are always high because there's lots of food out."

Browning said barn owl populations have been established for rodent control in many areas, including California vineyards and in oil palm nut plantations in southeast Asia.

"This program is not aimed at establishing a captive population, but rather an attempt to re-establish free-ranging barn owls in the county," Browning said.

"The owls are voracious feeders, have lots of babies and grow quickly. They are such prolific mousers that we hope they will have a depressing effect on the rodent population."

The decline

Barn owls were once common throughout the eastern United States. An open area owl, not a forest owl, they proliferated as pioneers cleared large areas of forest, making meadows, planting crops and building barns.

Heather Cuyler Jerry, with Annie the barn owl. Jerry directs the Moraine Preservation Fund's Species Re-introduction Program, which is providing the owl pairs the zoo will use in its program. Annie is used in the fund's education programs, not for breeding. (Andy Starnes, Post-Gazette)

Pittsburgh and Allegheny County lost most of their barn owls when they lost most of their barns. Urban growth and suburban sprawl crowded out farms and barns and deprived the owls of their homes and also the fields where they feasted.

"The number of small farms diminished in the 1940s, '50s and '60s, and it became harder for the owls to find nesting sites," Browning said. "The new barns that were built were often pre-fab and of tighter construction to keep pigeons out."

Barn owl populations were badly hurt in rural areas by the heavy use of farm and home pesticides beginning in the 1940s, which poisoned not only rodents but also the birds that ate them. The chemicals caused thin egg shells, which hurt reproduction.

The birds also frequently collided with cars as they hunted at night in the crown vetch along interstate roads. Barn owls are themselves the prey of the larger great horned owl, which still populates the city.

Taken together, the pressures on the barn owl population have been tremendous.

Barn owls in the wild live for an average of only three years and can have a mortality rate of up to 80 percent.

The owls have been wiped out in Indiana and Illinois. In Pennsylvania, they are listed as a "species of special concern" and until recently only five to 10 breeding pairs were in the state.

"The situation is hard for them and the populations have fallen so far over such a wide area that it's tough for them to recover without help," Browning said. "The most limiting factor is the loss of nesting sites and we feel the nest boxes will help."

Educational programs aimed at making people wise to the ways of the owls and urging them to limit or eliminate poisons are helping.

"We have talked to more than 600 farmers and children about the owls, urging them to stop using poison to control rodents," said Heather Cuyler Jerry, director of the Moraine Preservation Fund's Species Re-introduction Program. "For a long time people poisoned everything and sprayed everything. Now, slowly, they're starting to come around."

The road back

The Moraine Preservation Fund, which bred and released 96 osprey during a four-year program that ended in 1996, has been breeding barn owls at its "Owl Barn" -- actually a one-story cinderblock structure on the south shore of Lake Arthur in Moraine State Park -- for five years.

It will provide the first birds for the zoo's program.

Six breeding pairs are in the barn now, each in its own narrow room, and most of them sitting on eggs, which are white and slightly smaller than chicken eggs. They can lay as many as 10 eggs at a time, but most clutches are five or six eggs. And they can breed year around.

After they hatch, the chicks are kept in the rooms with their parents for 45 days, and fed dead mice supplied by Jerry and a squad of volunteers. Then the birds, already full grown at 14 inches tall and weighing up to a pound and a half, are taken to one of 12 "hacking barns" where they are released inside to develop and practice their hunting skills on live mice placed in a large tub.

The live mice cost about 25 cents each, and when the hacking barns are full the program can use 250 mice a day. They are the program's biggest expense.

After a week or two, Jerry opens the barn doors and the owls fly off to find their own meals.

"Their eyesight and hearing is keen. They can hunt in complete darkness," Jerry said earlier this month while holding the Preservation Fund's "show owl," Annie, whose sharp talons dug into a hand protected by a heavy leather falconer's glove.

"They are silent fliers. A mouse doesn't even see it coming."

Jerry said barn owls, sometimes called monkey-faced owls because of their heart-shaped facial disc feathers, kill their prey with their claws and then swallow it whole, unless it's a particularly large rodent, in which case they generally just bite off the head and leave the body.

To date, Jerry has released 190 barn owls and installed 300 nesting boxes.

But because the birds are cavity nesters, hunt at night and aren't very vocal, it's tough to judge the success of the repopulation program.

"It's a hard bird to track. It doesn't sit up in a tree and hoot," Jerry said. "We now know of a nesting pair in Lawrence County and one of our males has been sighted in Juniata County, where he's nested in a silo on an Amish farm.

"And they've been seeing quite a few around Saxonburg, where we've released a bunch. I'm sure the population is building."

Learning to hunt

Browning said the birds supplied to the zoo's program will hone their hunting skills in a new hacking aviary built this month on the zoo grounds, and at an aviary at the Pennsylvania Wildlife Center in Verona.

After a week or two they will be released and another batch will be brought in.

"We will release the owls in pulses," he said. "To get a number of breeding pairs established on the zoo grounds we will have to release more than 50 to create what we hope will be a self-sustaining, breeding population."

Eventually, Browning expects the owls to colonize other parts of the city. In addition to the nesting boxes on the zoo grounds, the birds could live in abandoned buildings within the city and cavities of large dead trees.

"There's no agreement with a wild bird that it will hang around once you release it, but I wouldn't be surprised if they couldn't find nesting areas across the river from the zoo in Fox Chapel and some of the city parks," Browning said. "The whole idea is to get them spread all across this region where they once thrived."

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