Evaluation of falconry as an economically viable co-management strategy to deter nuisance birds in leafy green fields

Best practices to reduce food safety risks from animal hazards during production and harvest have been published by the leafy greens industry. However, growers report that controlling nuisance birds (e.g., crows, blackbirds, starlings, geese), particularly social species that aggregate in large numbers and may cause focal or widespread fecal contamination, remains the most challenging area of co-management in leafy greens production. We propose to conduct a ‘proof of concept’ project to evaluate bird attractants and the use of commercial falconry, a popular and potentially highly effective method, as an economically viable co-management strategy to deter nuisance birds in leafy green fields. We will conduct two field trials (Spring, Fall) in the central California coast with the objectives to: 1) characterize key bird behavior and attractants in the leafy greens farmscape with a known history of bird intrusions and human pathogen-driven crop losses and 2) build data-driven support capacity for implementation of commercial falconry to reduce the risk of microbial contamination of leafy greens. Results from this study will be communicated widely in the leafy greens growing community to inform the industry of the potential viability of using falconry as an environmentally benign—or even beneficial—approach to non-lethal nuisance bird control.

Foodborne pathogen strains associated with fresh produce-related outbreaks have been found in environmental samples including fecal material from local wild or feral animal populations collected during root cause investigations. A wild animal shedding a zoonotic foodborne pathogen could contaminate plants directly through fecal deposition or indirectly via fecal contamination of agricultural water or soil in contact with the plants. Mitigation strategies to reduce food safety risks from animal hazards during production and harvest have been developed by the Arizona and California leafy greens industries through marketing agreements. However, growers report that controlling nuisance birds (e.g., crows, blackbirds, starlings, geese), particularly social species that aggregate in large numbers and may cause focal or widespread fecal contamination in agriculture fields, remains the most challenging area of co-management in fresh produce production(Research Priority 1.3.3). There is an urgent need to identify production practices and environmental factors that may attract and increase the likelihood of bird intrusion into produce production fields and to identify practical, cost-effective and sustainable means to deter birds from being attracted to produce production fields (Research Priority 2.2.1). To address this important area of applied produce food safety research, we propose to conduct a ‘proof of concept’ project to evaluate the use of commercial falconry as an economically viable co-management strategy to deter nuisance birds in leafy green fields. Trained raptors have been used for biological control of nuisance birds at airports, stadiums, agricultural fields and garbage dumps. Despite a number of professionals offering this service, the effects of falconry techniques for biological control of birds has rarely been quantified. Falconry may be an ideal method for preventing contamination of fresh market leafy greens because of the short time frame before and during harvest in which crop contamination from bird intrusions has the potential to be dangerous to humans. Currently, growers use human labor to implement bird harassment techniques in problem areas. These include launching small stones with slings, hand-propelled screamers, and pistol-launched pyrotechnics. We hypothesize that falconry is a highly effective and economically viable method for deterring birds from leafy green fields in the most vulnerable periods for potential zoonotic contamination prior to and during harvest. To test this hypothesis, we will conduct two field trials (Spring, Fall) in the central California coast leafy greens production region during the 2015 growing season with two main objectives: Objective 1: To characterize key bird behavior and attractants in the leafy greens farmscape with a known history of bird intrusions and human pathogen-driven crop losses. Objective 2: To build data-driven support capacity for implementation of commercial falconry to reduce the risk of microbial contamination of leafy greens. If successful, our goal is to bring a science-based focus and framework to evaluations of falconry in combination with other bird deterrent approaches (repellents, audio/visual devices), and to other growing regions with significant nuisance bird pressure including the southwest desert (Yuma, Imperial Valley).

Objective 1: To characterize key bird behavior and attractants in the leafy greens farmscape with a known history of bird intrusions and human pathogen-driven crop losses. A detailed questionnaire will be used to record landscape features, management practices, and animal damage costs that may be associated with bird intrusions. In collaboration with growers in the central California coast, the fields with a highest risk for significant nuisance bird intrusions will be selected and enrolled confidentially in the falconry pilot study (Objective 2). 

Objective 2: To build data-driven support capacity for implementation of commercial falconry to reduce the risk of microbial contamination of leafy greens. Commercial falconry will be evaluated as a non-lethal, effective, affordable, and sustainable approach to reduce the risk of microbial contamination of leafy greens due to bird intrusions. We will enroll test fields where falcons will be strategically deployed at different points during production and measure their effect on bird flocking and foraging behavior, and crop damage (fecal deposits, feeding) compared with nearby control fields. We will use data on application costs, effectiveness, value of the crop, and impact of the deterrent to estimate cost effectiveness of commercial falconry relative to potential reduced intrusion events and crop destruction.

• Surrounding crops, adjacent land use and season had a major influence on bird activity in and around leafy green fields enrolled in this study in Monterey County during the 2015 growing season. Important attractants included landscape features that provided food, shelter, and perching spots for nuisance birds. The predominant species observed in large flocks were Brewer’s blackbirds, red-winged blackbirds and European starlings. 

• Falconry was effective in reducing bird counts at leafy green fields during and after treatment, but the results were dependent on inter-related factors including season and bird abundance. In the central coast, falconry would likely be most cost-effective during the fall when large numbers of nuisance birds are known historically to enter the fields. 

• Falconry may also directly reduce bird intrusions and fecal contamination in leafy green fields, especially when >150 birds are present and seen foraging on the ground. 

• Several limitations inherent in the pilot study must be taken into consideration. For example, the lack of blocks with high and constant bird activity, the natural variability of bird presence and abundance between days, as well as production and environmental conditions, which made it difficult to draw robust conclusions. 

• Additional studies with more farms are needed to determine the effect of using falconry in combination with other non-lethal bird abatement approaches (e.g., audio-visual deterrents) to maximize the cost-effectiveness of this approach. We also recommend evaluation of using the falcons for longer treatment periods (>5 days) and follow-up posttreatment for more than 3 days to determine the length of the effect. 

• Ultimately, management of pest birds requires an integrated approach based on the unique situation of each ranch and each problem. The findings of this proof-of-concept study emphasize the continued importance of considering adjacent land use during environmental assessments before planting and harvest. Recommendations for growers include taking into account the management of pest birds performed by neighboring ranches and considering the use of falconry to decrease bird intrusions into fields when flocking birds are most abundant.