Data from: Assessing foodborne pathogen survival in bird feces to co-manage farms for bird conservation, production, and food safety

Because birds can carry foodborne pathogens, widespread concern exists
that birds impose food-safety risks to farms. Growers are thus often
encouraged to deter birds and forego harvesting crops near bird feces
(e.g., no-harvest buffers). Developing a holistic understanding of the
pathogen spillover process– from individual infection to pathogen
persistence on crops– is essential to understand and manage food-safety
risks associated with birds. Here, we coupled field and greenhouse
experiments to understand the relative risks associated with different
bird species on California farms. We first compared E. coli survival in
bird feces on lettuce, soil, and plastic mulch to identify where pathogens
are likely to persist. Next, we quantified pathogen survival in feces from
10 bird species to identify higher-risk species. Finally, we combined
pathogen survival data with bird surveys and fecal transects to assess
food-safety risks across 29 California lettuce farms. E. coli abundance
rapidly declined in bird feces, but rates varied across substrates. E.
coli survival was higher on lettuce compared to soil and plastic mulch,
likely because of lettuce’s cooler and wetter microclimate. E. coli
persistence was also much higher in feces from larger birds—which produce
larger feces—than small songbirds. Importantly, minimal differences in
persistence among species were observed after all feces were standardized
to the same mass. Though bird feces were common on farms, most birds
entering farms, contacting crops, and defecating on crops were small
songbirds that defecate small feces. Coupled with our finding that ~90% of
feces were deposited on soil, these results suggest that most birds on
farms present relatively low food-safety risks. Synthesis and
applications. Growers are often encouraged to deter all bird species and
forego harvesting crops near all bird feces, but our work suggests not all
birds and feces pose the same food-safety risks. If growers ignored small
bird feces on soil, then we estimate that the area of California lettuce
farms affected by no-harvest buffers could decrease from ~10.3% to ~2.7%.
More broadly, our results suggest farmers could promote small,
insect-eating birds by erecting nest-boxes or preserving habitat without
necessarily compromising food safety.