Ornithologists call the great flocks of starlings flying in tight, synchronized clouds in the sky "murmurations."
The Oregon Department of Transportation calls them a nuisance.
Each winter thousands of starlings congregate to roost on the two spans of the Interstate Bridge that connects Oregon and Washington over the Columbia River via Interstate 5.
The bird's droppings — in addition to being unhealthy for bicyclists, pedestrians and bridge workers — coat the catwalks and bridge surfaces, leading to the aging structure's corrosion.
On Wednesday, ODOT will again begin firing propane-powered orchard cannons to keep the birds away.
Kimberly Dinwiddie, an ODOT spokeswoman, said one cannon will be used near the southbound span on Wednesday, Jan. 30 and Feb. 11. The cannon blasts will sound off from 4:15 to 4:50 p.m. The cannon will fire multiple times in intervals ranging from 2 seconds to 20 seconds apart.
Dinwiddie said the random firing schedule and the use of fewer or more cannons will prevent the birds from becoming accustomed to the noise and its location.
According to an ODOT website information page, the "noise from the cannons creates stress, upsetting their biorhythms and causing them to seek less stressful places to roost."
ODOT began testing the use of orchard cannons to keep the birds away in October 2002, and began regularly firing them the next year.
-- Stuart Tomlinson
stomlinson@oregonian.com
503-221-8313
@ORweather