A trait-based framework for predicting foodborne pathogen risk from wild birds.

Recent foodborne illness outbreaks have heightened pressures on growers to deter wildlife from farms, jeopardizing conservation efforts. However, it remains unclear which species, particularly birds, pose the greatest risk to food safety. Using >11,000 pathogen tests and 1565 bird surveys covering 139 bird species from across the western United States, we examined the importance of 11 traits in mediating wild bird risk to food safety. We tested whether traits associated with pathogen exposure (e.g., habitat associations, movement, and foraging strategy) and pace-of-life (clutch size and generation length) mediated foodborne pathogen prevalence and proclivities to enter farm fields and defecate on crops. Campylobacter spp. were the most prevalent enteric pathogen (8.0%), while Salmonella and Shiga-toxin producing Escherichia coli (STEC) were rare (0.46% and 0.22% prevalence, respectively). We found that several traits related to pathogen exposure predicted pathogen prevalence. Specifically, Campylobacter and STEC-associated virulence genes were more often detected in species associated with cattle feedlots and bird feeders, respectively. Campylobacter was also more prevalent in species that consumed plants and had longer generation lengths. We found that species associated with feedlots were more likely to enter fields and defecate on crops. Our results indicated that canopy-foraging insectivores were less likely to deposit foodborne pathogens on crops, suggesting growers may be able to promote pest-eating birds and birds of conservation concern (e.g., via nest boxes) without necessarily compromising food safety. As such, promoting insectivorous birds may represent a win-win-win for bird conservation, crop production, and food safety. Collectively, our results suggest that separating crop production from livestock farming may be the best way to lower food safety risks from birds. More broadly, our trait-based framework suggests a path forward for co-managing wildlife conservation and food safety risks in farmlands by providing a strategy for holistically evaluating the food safety risks of wild animals, including under-studied species.

Interactive effects of multiscale diversification practices on farmland bird stress.

Farmland diversification practices (i.e., methods used to produce food sustainably by enhancing biodiversity in cropping systems) are sometimes considered beneficial to both agriculture and biodiversity, but most studies of these practices rely on species richness, diversity, or abundance as a proxy for habitat quality. Biodiversity assessments may miss early clues that populations are imperiled when species presence does not imply persistence. Physiological stress indicators may help identify low-quality habitats before population declines occur. We explored how avian stress indicators respond to on-farm management practices and surrounding seminatural area (1-km radius) across 21 California strawberry farms. We examined whether commonly used biodiversity metrics correlate with stress responses in wild birds. We used ∼1000 blood and feather samples and body mass and wing chord measurements, mostly from passerines, to test the effects of diversification practices on four physiological stress indicators: heterophil to lymphocyte ratios (H:L), body condition, hematocrit values, and feather growth rates of individual birds. We then tested the relationship between physiological stress indicators and species richness, abundance, occurrence, and diversity derived from 285 bird point count surveys. After accounting for other biological drivers, landscape context mediated the effect of local farm management on H:L and body condition. Local diversification practices were associated with reduced individual stress in intensive agricultural landscapes but increased it in landscapes surrounded by relatively more seminatural area. Feathers grew more slowly in landscapes dominated by strawberry production, suggesting that nutritional condition was lower here than in landscapes with more crop types and seminatural areas. We found scant evidence that species richness, abundance, occurrence, or diversity metrics were correlated with the individual's physiological stress, suggesting that reliance on these metrics may obscure the impacts of management on species persistence. Our findings underscore the importance of considering landscape context when designing local management strategies to promote wildlife conservation.

Algunas veces se considera a las prácticas de diversificación agrícola (es decir, los métodos usados para producir alimentos de manera sustentable mediante el enriquecimiento de la biodiversidad en los sistemas de cultivo) como benéficas para la agricultura y la biodiversidad, pero la mayoría de los estudios sobre estas prácticas dependen de la riqueza, abundancia o diversidad de especies como indicadores de la calidad del hábitat. Las valoraciones de la biodiversidad pueden ignorar las señales tempranas de una población en peligro cuando la presencia de la especie no implica persistencia. Los indicadores de estrés fisiológico pueden auxiliar en la identificación de hábitats de baja calidad antes de que ocurra la declinación poblacional. Analizamos las respuestas de los indicadores de estrés en aves al manejo en las granjas y áreas seminaturales circundantes (1 km de radio) de 21 cultivos de fresas en California. Evaluamos si las medidas comunes de biodiversidad se correlacionan con las respuestas al estrés de las aves silvestres. Usamos aproximadamente mil muestras de sangre y plumas y medidas de masa corporal y cuerda alar, la mayoría de paseriformes, para analizar los efectos de las prácticas de diversificación sobre cuatro indicadores de estrés fisiológico: la relación heterófilos/linfocitos (H:L), condición corporal; valores hematocritos; y la tasa de crecimiento de las plumas en aves individuales. Después probamos la relación entre los indicadores de estrés fisiológicos y la riqueza, abundancia, presencia y diversidad de especies tomadas de 285 conteos por puntos de aves. Después de considerar otros factores biológicos, el contexto del paisaje medió el efecto de la gestión de las granjas locales sobre la H:L y la condición corporal. Las prácticas locales de diversificación estuvieron asociadas con una reducción en el estrés individual en los paisajes con agricultura intensiva; sin embargo, el estrés aumentó en los paisajes rodeados por áreas relativamente más seminaturales. Encontramos poca evidencia que respalde que las medidas de riqueza, abundancia, presencia y diversidad de especies estuvieran correlacionadas con el estrés fisiológico de los individuos, lo que sugiere que depender de estas medidas puede nublar el impacto de la gestión sobre la persistencia de las especies. Nuestros descubrimientos apuntalan lo importante que es considerar el contexto del paisaje cuando se diseñan las estrategias de gestión local para promover la conservación de la fauna.

Joint environmental and social benefits from diversified agriculture.

Agricultural simplification continues to expand at the expense of more diverse forms of agriculture. This simplification, for example, in the form of intensively managed monocultures, poses a risk to keeping the world within safe and just Earth system boundaries. Here, we estimated how agricultural diversification simultaneously affects social and environmental outcomes. Drawing from 24 studies in 11 countries across 2655 farms, we show how five diversification strategies focusing on livestock, crops, soils, noncrop plantings, and water conservation benefit social (e.g., human well-being, yields, and food security) and environmental (e.g., biodiversity, ecosystem services, and reduced environmental externalities) outcomes. We found that applying multiple diversification strategies creates more positive outcomes than individual management strategies alone. To realize these benefits, well-designed policies are needed to incentivize the adoption of multiple diversification strategies in unison.

Agriculture and hot temperatures interactively erode the nest success of habitat generalist birds across the United States.

Habitat conversion and climate change are fundamental drivers of biodiversity loss worldwide but are often analyzed in isolation. We used a continental-scale, decades-long database of more than 150,000 bird nesting attempts to explore how extreme heat affects avian reproduction in forests, grasslands, and agricultural and developed areas across the US. We found that in forests, extreme heat increased nest success, but birds nesting in agricultural settings were much less likely to successfully fledge young when temperatures reached anomalously high levels. Species that build exposed cup nests and species of higher conservation concern were particularly vulnerable to maximum temperature anomalies in agricultural settings. Finally, future projections suggested that ongoing climate change may exacerbate the negative effects of habitat conversion on avian nesting success, thereby compromising conservation efforts in human-dominated landscapes.