Laser scarecrows could offer a sustainable solution to protect crops from birds

Crop damage caused by birds costs millions of dollars each year. Now, researchers from the University of Florida and the University of Rhode Island in the United States are studying the effectiveness of laser scarecrows, a high-tech solution that uses light to deter birds.

In a new study published in Pest Control ScienceThey presented captive flocks of European starlings with fresh ears of sweet corn and demonstrated that devices emitting a moving laser beam can significantly mitigate crop damage, up to 20 m from the laser device.

Kathryn Sieving, professor of wildlife ecology and conservation at the University of Florida and corresponding author of the research, explained that more growers are looking for inexpensive, portable laser units like those tested in the research. .

“Growers need big effects at affordable prices, and if they can spend $300-$500 each on lasers to protect large fields for 1-3 weeks instead of more expensive options such as “hire people to patrol with dogs, hawks or guns, then lasers would be beneficial,” she said.

One reason lasers are a particularly effective solution for protecting sweet corn is the short time before harvest during which birds target the crop, known as the “window of vulnerability.” This short window reduces the risk of birds becoming desensitized to lasers.

Sieving explained: “Lasers are being widely explored for crops with short windows of vulnerability, such as sweet corn. They seem to work very well, especially when different non-lethal deterrents are combined (e.g. lasers with loud noises). Birds only attack sweet crops. corn during the brief maturation phase (called the milking stage) and this lasts only 5 to 10 days. So, as soon as it ripens, the harvest begins.

“Therefore, in sweet corn, the protection does not need to last very long and the lasers seem to work well – surprising birds leaving the fields with lasers, reducing damage during the milking stages of well more than 20%.”

The study involved two types of trials: stick trials, in which ears of fresh sweet corn were mounted on sticks at different distances from the laser units, and natural trials, in which birds fed on ripe corn grown from seed in a flight enclosure. Laser and control treatments were alternated daily for five days, allowing researchers to assess the birds’ response to repeated laser exposure.

“We designed the stick trials to increase the sample size for more robust results. Natural corn matures over several weeks but is then only attractive to birds for two weeks. Our planted crop “So with the stick experiments on corn, we could study the effects on a small scale and increase the sample sizes,” Sieving said.

Results showed that lasers reduced sweet corn damage marginally in stick trials and dramatically in natural trials. Explaining this difference in effectiveness, Sieving noted: “The sticks we presented the corn on were sturdy and the birds could probably perch and feed on the corn while sometimes avoiding the laser layer. Natural corn stalks are fragile, however, and birds would bounce in and out of the laser layer without control. So, just like in larger fields, it appears that natural corn makes lasers very effective.

The researchers also looked at the impact of distance from the lasers on the extent of damage to sweet corn. They found that there was effective deterrence up to 20 m from the laser source; however, beyond this distance, crop damage increased, with little or no deterrence at 30 m. Sieving notes: “The data showing this relationship with distance are really the only data of this type and were able to be obtained because we worked with captive birds.”

However, she explained that in real-world contexts, this effect seems unimportant. “In open fields, birds simply leave a field with detectable laser protection and fly away from its influence. It appears that a single laser per field can often be enough to keep birds largely out of a field. So , the small-scale spatial effects could only apply if the birds were too determined to feed a small area, so a grower might need to add a few laser units with overlapping ranges.

Sieving hopes laser scarecrows can offer a sustainable solution for protecting crops with short windows of vulnerability.

“Lasers are quiet, unlike acoustic deterrents (loud bangs, other noises occurring several times per hour), which can be very disturbing to neighbors and workers. Lethal deterrents require permits, time and labor to be applied, as well as potentially toxic side effects on wildlife, soil and water are often unacceptable.