Small Birds and Their Droppings: Understanding Food Safety Risks You Need to Know

Farmers don’t need a fancy degree or complex tools to figure out if bird droppings near their crops pose a food safety risk. It mostly comes down to a simple question: How big is the poop?

This insight comes from a study by researchers at the University of California, Davis, published in the Journal of Applied Ecology. The research suggests that understanding food-safety risks related to wildlife can help farmers protect their crops while also supporting biodiversity.

Since the 2006 E. coli outbreak linked to leafy greens, farmers have been more cautious about wildlife. Many have been advised to stay at least three feet away from any area where birds have left droppings. This has led some farmers to hesitate in adopting conservation practices on their land, fearing it could jeopardize their market contracts or food safety audits.

Lead researcher Austin Spence explained that they wanted to understand the actual risks that wild birds pose to food safety. They looked into which birds might carry pathogens and how long these pathogens could survive in bird droppings. Their findings indicate that farming and conservation can go hand in hand.

Understanding Pathogen Survival

The research involved studying nearly 10,000 birds across 29 lettuce farms along California’s Central Coast. This included hours of observing various birds and collecting poop samples to test the survival of E. coli. They found a striking result: smaller bird droppings carry a lower risk of foodborne pathogens, which are rare in birds overall.

Spence noted, “Larger birds produce bigger feces, which are more likely to harbor pathogens. In contrast, smaller birds have tiny droppings where germs die off quickly. So, rather than identifying every bird, farmers just need to pay attention to the size of the feces. If it looks like a quarter, avoid harvesting nearby. If it’s just a tiny speck, you’re probably safe.”

Finding the Right Balance

The type of surface also affects how long pathogens can linger. The study discovered that E. coli lasts longer on lettuce than on soil or plastic. Fortunately, most birds observed in the study were small and tended to defecate on soil, where the pathogens disappear quickly. By skipping no-harvest areas in low-risk zones, farmers could potentially increase their harvest by about 10%.

“Customer fears about bird contamination might be overblown,” said Daniel Karp, another senior author of the study. “E. coli and Salmonella are extremely rare in wild birds on farms, and most of the pathogens die off quickly.”

This study presents new methods for farmers to balance the need for conservation with food safety concerns. For instance, they could install birdhouses to attract small birds that eat insects, helping manage pests without increasing the risk of contamination.

The research adds to a growing body of evidence suggesting that removing natural habitats doesn’t necessarily enhance food safety. According to Karp, “No studies so far show that taking away habitat improves safety. In fact, keeping it may lure more small, insect-eating birds that are less likely to carry germs. Our study empowers farmers to maintain habitats that support wildlife again.”

The research team included contributors from several universities and organizations, with funding from the Center for Produce Safety, the California Department of Food and Agriculture, and the U.S. Department of Agriculture.