BRUNSWICK, Maine — In an effort to ensure a smooth flight for all, wildlife officials have relocated four of six snowy owls that showed up at Brunswick Executive Airport this winter, moving the spectacular creatures at least 20 miles away along their migratory route to eliminate the possibility of their return.

Biologists from the U.S. Department of Agriculture Wildlife Services first set traps in mid-January and have captured and relocated four of the birds while continuing to look for two remaining owls spotted this winter, according to Wildlife Services state director Robin Dyer.

Officials are concerned about the safety of the aircraft and the birds, which when struck by a plane can cause significant damage to both. In fact, though such strikes are rare, snowy owls are one of the species most likely to cause damage when struck by an aircraft, Dyer said, in part because of their body mass, density and habit of flying low.

“They’re big owls and slow-moving animals, so for safety reasons we have them removed” said Steve Levesque, executive director of the Midcoast Regional Redevelopment Authority, the entity charged with redeveloping the former Navy base where the airport is located. Levesque referred to the airliner that crashed on the Hudson River in New York City in 2009 after it struck a flock of Canada geese.

Maine has experienced an “irruption,” or large influx of the owls during the past couple of winters, according to wildlife biologists. The state’s many airports are along the owls migratory route, and the birds are drawn to airports because the environment is similar to that of their home turf, the tundra, Dyer said. Airport fields also are usually home to many rodents, one of the owls’ primary food sources.

In the summer, the airport blasts an “air gun” to keep larger birds away, Levesque said. But in the winter, snowy owls that live the rest of the year in the Arctic travel back and forth during their migration.

According to Dyer, snowy owls are “very resistant” to deterrents commonly used at airports, such as pyrotechnics. For the past two winters, biologists have set bow nets baited with live pigeons to catch the owls.

The owls are lured into the trap by the pigeons and, once they’re inside the catch zone, a net is deployed remotely by a biologist. The owls then are banded with a numbered plastic band around a leg so biologists can learn about successful relocation distances and other information.

Dyer said moving the owls at least 20 miles away in the direction of their migratory path results in only about 1 percent of the birds returning to the airport.

But with snow and ice still rimming the runways, despite the calendar, two snowy owls still remain in the area of the airport. Lucky ornithologists might catch a glimpse. Last year, snowy owls were still in the area in late April, stopping as they migrate north to their breeding grounds.