No one wants poop on their cherries. Farmers in northern Michigan could get some help on this fecal matter from some feathered allies. Small falcons called the American kestrel help deter smaller birds that like to snack on the fruit when it is growing. By shooing cherry-pecking birds away, these raptors prevent them from contaminating crops with their poop. The findings are detailed in a study published November 27 in the Journal of Applied Ecology.
American kestrels are the smallest falcon species at only nine inches from head to tail. They live throughout North and South America. While in flight, they hover in mid-air as they scan the ground below for insects, mice, and small birds to eat. Eating those smaller avians is what could help keep crops clean from excess bird poop, which can contaminate the fruit with pathogens that make people sick.Â
“It’s hard to keep birds out of crops,” Olivia Smith, a study co-author and Michigan State University agroecologist, said in a statement.Â
Other methods to keep unwanted birds out of crops include scarecrows, sprays, nests, and noise makers. These approaches can be costly and do not always yield great results. According to the team, even with control measures in place, sweet cherry growers in states Michigan, Washington, California, and Oregon can lose anywhere from five to 30 percent of their crops every year to contamination. Â
In this new study, the team was curious if enticing these predators to patrol orchards could help reduce the risks. They installed nest boxes in eight sweet cherry orchards in northern Michigan. The kestrels use tree cavities and other small spaces to raise their chicks and were quick to move into the orchards. They then took note of all of the bird species that they could see and hear as harvest time approached in July.
When the kestrels were flying nearby, robins, grackles, and starlings were much less likely to visit orchards and eat fruit. By scaring away these visitors, the kestrels reduced the likelihood of cherry damage more than tenfold.
As far as the other birds’ poop, the team found fewer signs that they were doing their business on the cherry trees. The kestrels were associated with a three-fold reduction in droppings spotted on tree branches.
The team noted that, of course, the kestrels also poop, but the number of fruit-eating birds that they keep away from an orchard makes up for it. The team found that cherry trees closer to the kestrel’s nest boxes were less likely to have droppings on them.Â
Olivia Smith/ Michigan State University.
A DNA analysis revealed that 10 percent of the droppings contained Campylobacter. These bacteria commonly cause foodborne illness. However, the team says that none of the foodborne illness outbreaks caused by Campylobacter have been linked to cherries and it might be too early to entirely blame birds for contaminated crops. Only one outbreak has been traced to birds. In 2008, a Campylobacter outbreak linked to migratory cranes was reported in pea fields in Alaska.
The study still suggests that kestrels could be a way to improve food safety in other crops that have been associated with outbreaks, such as leafy greens.
“They’re really good at keeping the amount of poop down,” Smith said. “That means fewer opportunities for transmission.Â
Smith added that this won’t solve all of the bird problems that farmers face, namely that kestrels are more likely to stay in some regions over others. However, it could still help keep those crops clear and healthy.Â
“Certainly, kestrels poop too,” said study co-author and integrative biologist Catherine Lindell. “But it’s a low-cost, low maintenance tool for growers to use in their bird management toolbox.”
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