Daily Yomiuri

April 3, 2004

Fending off annoying birds

Asami Nagai / Daily Yomiuri Staff Writer

When Prof. Yukio Hirose of Kanazawa University expressed his warmest gratitude for pigeons and crows upon receiving the Ig Nobel Chemistry Prize (a parody of the Nobel Prize) in October, the audience at Harvard University exploded into cheers.

"I said something like, 'I had worked hard in hopes of going to Sweden, but the birds of Kanazawa pecked at my back and drove me to Cambridge (where Harvard University is located) instead,'" Hirose recounted with a straight face. "Then, I added that I felt grateful for the birds, despite what they did."

Grateful for what? As it happens, it is thanks to the birds of his hometown that Hirose, 63, was able to find the answer to a question that puzzled him 45 years ago and learned that his findings could be publicly beneficial.

Last year, he created a bronze alloy that repulsed birds, based on his investigation of the materials in a bronze statue in Kanazawa that had failed to attract any pigeons while it was standing.

After the local newspaper, and then a weekly, covered his findings, he started to receive inquiries, one of which asked him whether he was interested in being nominated for the Ig Nobel Prize.

This joke award has been offered for the past 13 years by the U.S. science humor magazine Annals of Improbable Research, honoring achievements that first make people laugh then make them think. Hardly ignoble stuff, if you think about it.

Initially, Hirose was not very keen on the award.

"Now, I understand the concept very well. But my achievement, from the very beginning, was no laughing matter," Hirose said. "Still, I had been told to make the audience laugh in my one-minute speech at the awards ceremony, so I planned to tip 1 dollars to the girl who is supposed to come to stop me when my time is up."

As he had planned, this joke worked tremendously well. But, according to Hirose, the audience seemed to giggle at everything he said in his speech as well.

Hirose, during his stay in Cambridge, learned that Ig Noble winners were actually selected for achievements that were deemed good for the public.

"In the past, a man who invented a special underwear designed to remove noxious fumes before they escape was awarded the medicine prize," Hirose said. "This man had to endure the awful smell of his wife's flatulence, and his recounting of this episode induced laughter. But his idea was prized not only because it was humorous but also because it was, well, practical."

Hirose added that at hospitals today, bad odors produced by helpless patients is a big issue. "Just like with his achievement, mine was probably evaluated for its practicality. They probably expected it to someday help people."

He is right. City dwellers around the world were already fed up with crows and pigeons that dirtied their neighborhoods either by scattering garbage or with their droppings.

Then came bird flu. Overnight, wild birds went from being a nuisance to becoming deadly stealth bombers.

In the past month or so, his Kanazawa University office has been inundated with inquiries from people fanatically looking for solutions to fend off those birds. "That's the worst part of the fame wining the Ig Nobel has given me," he joked. "I've been extremely busy ever since!"

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Tenacity leads to development

Hirose is not an ornithologist but a material scientist. At age 18, while studying engineering as a first-year student at Kanazawa University, he began wondering how a statue in Kenrokuen, a park near the university back then, managed to remain completely clean of pigeons' droppings, while nearby trees and other statues were usually painted white with them.

Visiting the park frequently for various reasons, Hirose came to realize that this statue of Prince Yamato Takeru, built in 1880, attracted few, if any, birds. "I used to come to the park to party or nap, and found there were lots of birds perched around there," Hirose said. "But they always seemed to prefer tree branches to the statue's head and shoulders, which I found very strange."

At that time, he did not try to investigate the cause. But he unexpectedly returned to the problem when, as a metal fatigue expert, he was given an opportunity to study the statue's materials when it was pulled down for repair work in 1989. On the 5.5-meter bronze statue, Hirose found no white splotches, again making him ponder why.

As he investigated the composition of the material, he recalled a statement in the book, Studies in Ancient Technology, by R.J. Forbes. Hirose was responsible for translating Chapter 5, which deals with elements that include antimony and arsenic. The statement he read was about how arsenic is lethal to birds.

The moment Hirose discovered the high content of arsenic in the statue, he was almost positive that this was what was driving the pigeons away.

"Unlike the Yamato Takeru statue, Takamori Saigo's statue in Ueno Park, Tokyo, is stained badly with droppings," Hirose said. "The arsenic content in the Saigo statue is 2 percent to 3 percent, while the alloy used in the Yamato Takeru statue contains more than 10 percent arsenic." In fact, the content is not even. It is 2 percent at the head but reaches as much as 15 percent at the feet.
Further research showed that that the high arsenic content helped the bronze alloy melt at 1,000 C, compared to the 1,300 C needed to melt bronze with a 2 percent arsenic content. When the Kanazawa statue was built, around 1880, artisans who had access to only relatively primitve furnaces had no choice but to mix a lot of arsenic with the bronze to be able to create a bronze statue.

Nearly 10 years after making the connection between birds and arsenic, Hirose finally had a chance to implement his theory.
About a year ago, Hirose, then the director of his alma mater's Cooperative Research Center, met with a local businessman who came to see Hirose to ask whether he knew of an effective way to remove sticky flyers from walls and phone booths.

As this businessman turned his back, Hirose saw that his shoulders were dotted with a white substance, which turned out to be bird droppings. As it happened, the man was having a hard time with pigeons that congregated near his office.

By this time, many people had brought the issue of bird droppings to the center, hoping Hirose could offer a solution.

In response, he created copper alloy pieces that had a 10 percent arsenic content that also contained lead and tin as well as other elements. As a solid object, this alloy is perfectly safe. But if burned at higher than 1,000 C, a vapor containing arsenic--lethal, of course--is emitted. In other words, people who happen to inhale the vapor will instantly, in Hirose's words, "be sent to the next world."
This discourages many town officials who are desperately seeking antibird measures.

"I was approached by Tokyo metropolitan government officials," Hirose said. "When they learned that a fatal vapor could be created if there was a fire, they became hesitant about using the alloy. They said they couldn't use it in any populated area, where fires very well could occur."

Hirose risked his life in attempting to create the alloy. Assisted by one of his former students, he worked in a private lab he built on the land lot he owned, wearing a protective mask and a suit.

Even this precautionary measure, however, didn't prevent Hirose from sometimes feeling a little queasy.

Having created the bronze, he placed pieces of it in a circle in front of JR Kanazawa Station, where pigeons usually flock.

Hirose videotaped the area around the circle for six hours a day. Not a single pigeon dared to come within a meter of the circle, despite their favorite food being scattered on the ground.

"It was amazing," he said. "Pigeons squawked at the bronze, kind of like how a woman sniffs at a man she doesn't like." After he removed the plates, the birds came back to eat the food.

Next, he placed the bronze on the roofs of factories where numerous crows often gather, as well as in garbage piles and a cowshed. Crows chose to stay away from the metal plates.

Still, he needed to prove the bronze could be used safely. To do so, he chose several goldfish to be his guinea pigs. He left a piece of the bronze in a water tank for a month, and kept several goldfish in it for a few more months. The fish all survived.

"The amount of toxic substance that escaped into the water from the bronze was 0.014 milligrams for every liter," Hirose said. "This figure is far below the nation's environmental standard of 0.3 milligrams. Even hot water at a nearby spa has a higher arsenic content."
But just to be on the safe side, he tested its safety one more time. "I rubbed the alloy onto some candy and ate it. But nothing serious has happened to me," Hirose said matter-of-factly.

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Secrets of effectiveness

Despite all this talk about arsenic's poisonous nature, Hirose attributes the miraculous power of the alloy to either the smell of the metal or the electromagnetic waves or negative ions produced by it.

Hirose's explanation suddenly turned scientific. "Because the arsenic content is relatively high in this alloy, and because it contains several other elements such as lead and silicon, the bronze becomes a good semiconductor. This means that when light hits it, it emits a weak electric current," he said.

He believes the birds are repelled by this current.

He also gives much credence to the negative ion theory, because he found that one square meter of the bronze contained about 1,000 negative ions. Negative ions in small amounts can be good for the health, but larger amounts, like that found in the bronze, could have negative effects.

Hirose also decided to study the ecology of crows. This inquisitive metal scientist requested four crows from Kanazawa municipal workers who have been catching the birds.

In the last several months, he tried various experiments with the crows, which he kept in a cage. Through them, he began to suspect that light-emitting diodes may be effective in repelling crows as well. When he focused blue light on the crows, they tried to avoid it, Hirose said.

Now, Hirose is adding the final touch to bird-repellent measures that pose less of risk than his high-arsenic bronze alloy. One of the works-in-progress is a net woven with a substance that generates large volumes of negative ions.

"Even though I have an Ig Nobel Prize, I have not lost hope for the real Nobel," Hirose grinned. "I'll continue to work hard on my projects." But he's also looking to solve other problems, like athlete's foot and balding.

"It's widely believed that whoever finds the ultimate cure for these problems very likely will win a Nobel Prize. And I'm very close to doing just that."