Pigeons leave their mark on N.D. bridges

AssociatedPress

Pigeons are more of a nuisance than a threat to North Dakota’s bridges, according to the state Department of Transportation.

Pigeon droppings are known to be corrosive, and the amount of dung that had built up on the Interstate 35W bridge in Minneapolis was one of the factors that bridge inspectors say worked against the structure. Investigators are continuing to study which factors caused the fatal collapse on Aug. 1.

North Dakota inspectors haven’t found pigeon dung, while plentiful, to be affecting the integrity of any bridge, said Terry Udland, chief bridge engineer with the state Department of Transportation.

“The bottom line is we are aware of it. We have never really had what we consider an issue with it,” he said. “It’s been pretty much more of a nuisance issue.”

Pigeon droppings contain ammonia and acids that can lead to corrosion and rust. Udland said the lack of notable damage on North Dakota bridges might be due to the type of primer and paint providing a protective coat.

Pigeon dung presents more of a problem as a source of disease. The transportation department hires a contractor to clean up the mess before inspectors go in to do their work.

The department doesn’t consider the clean-up costs to be significant, Udland said. Still, because of the nuisance, the department has tried some techniques for discouraging pigeons from roosting where they’re not wanted. It has found that keeping the birds away isn’t easy.

This past winter, the U.S. Department of Agriculture conducted a pigeon eradication program in Minot at the request of First District Health Unit, which was responding to concerns of downtown business owners. The eradication program included the downtown area and a grain elevator east of town and was funded by the businesses.

Phil Mastrangelo, state director for USDA Wildlife Services in Bismarck, estimated nearly 700 pigeons were removed, primarily through trapping and euthanization.

While not a cure, the program did reduce the scope of the problem, said Tim Greenheck, a former downtown property owner who coordinated the fund-raising for the program.

“It absolutely made a difference. It absolutely helped, but it would have to be an ongoing endeavor to really be what most people would deem successful,” he said.

A study completed in April for the Wisconsin Department of Transportation concluded that trapping or shooting pigeons alone isn’t effective in the long term. Successful pigeon control requires a blending of more than one approach, according to the researchers.

Preventive measures include spikes, netting, sticky gels, sonic and ultrasonic devices, scarecrows like snakes or owls and electrified perches. The Wisconsin study found places in the country that have used repellents with success. They found others struggling to get anything to work – like folks along the Ohio River who struck out with scarecrows, barbed wire, predator calls, cannons and chemicals that make the birds’ feet burn.

Using a combination of prevention strategies can produce results, said Mona Zemsky, technical consultant with Bird-X, a Chicago company that markets repellents at (www.bird-x.com).

Some of the most popular repellents are bird netting made of a polyethylene or polypropylene and metal strips with spikes that inhibit roosting. A sticky gel, applied with a caulking gun, works the same way in creating an unattractive roosting environment.

“Physical barriers are easy because they do the job permanently,” Zemsky said. “While they take a little bit of labor upfront, it’s of one those things you won’t have to think about again. That’s what a lot of municipalities want is a one-time fix.”

Electronic options also are popular, she said. There are ultrasonic devices that humans can’t hear and sonic devices that make intermittent, natural sounds, such as bird distress cries or predator cries.

The amount spent on a device or combination of devices can be more than offset by savings in property damage and avoiding disease or injury lawsuits, Zemsky said. Birds and their droppings can spread more than 60 diseases to humans, she said.

Zemsky said the Minneapolis bridge collapse has generated publicity for the pigeon issue, which is a good thing.

“We are happy it’s getting attention because it’s a very important topic, but it’s not like this is brand new,” she said, noting Bird-X has been in business for 44 years.

Transportation departments have been aware of the issue for a long time, but some are getting more serious about it. The state of Colorado is studying pigeon repellents to find which are the most effective and cost-efficient to use with its bridges. It also is looking into future bridge designs that could make the structures less attractive to birds.