Organic Farming Increases Bird Activity
Birds from organic farms exhibit more vitality than those who live on conventional farms, according to a recent French study. Organic birds exhibit a higher rate of active behaviors including aggression, escape attempts (when caught for the purpose of this study), and predator-deterring mechanisms. Birds provide beneficial services that fall into all four ecosystem service categories.
They contribute to:
- Provisioning services, which involve food production,
- Regulating services when they naturally control pests through insect predation and offer pollination to crops and non-crop plants,
- Supporting services when they contribute to the cycling of nutrients in the system, and
- Cultural services where they add spiritual value to landscapes
Their presence in farms is also valuable simply by adding biodiversity, which helps organic farmers meet the biodiversity guidance requirements for the national organic standards.
Birds are negatively affected by air pollutants like pesticides and herbicides, which are used by many non-organic farms in order to control weeds and diseases. Past studies have indicated that bird diversity is higher on organic farms than on conventional farms, but there have been few studies comparing the life history of individual birds. Chronic sublethal exposure to pesticides–non-acute exposure that does not result in immediate death–is suspected to weaken birds because energy is required to neutralize their toxic effects.
Researchers surveyed farms in Central-Western France, sampling from nesting sites in organic and non-organic farms. Birds were netted during the breeding season, and their vitality was quantitatively measured, observing vigor and predator-deterrent behaviors. Researchers assessed the vigor of the birds by systematically counting their escape attempts, distress calls, and pecks. To quantify predator-deterrent behavior, predator-like stimuli were introduced and the length of tonic immobility–“playing dead”–was measured; tonic immobility is an effective tool for birds to avoid predation. Additionally, researchers recorded breath rate and body condition, measured by mass index.
Birds sourced from organic farms displayed a higher quantity of behaviors associated with activity. Median flee attempts were nearly doubled on organic farms compared to conventional, and organic birds also expressed significantly more pecks and distress calls. These aggressive behaviors were displayed towards researchers from both habitats, however, the decreased intensity of aggressive behaviors by birds from non-organic farms demonstrates how pesticide exposure can dampen bird energy.
Additionally, organic birds exhibited longer periods of threat-induced paralysis (i.e. “playing dead”), indicating superior predator avoidance. These results suggest that pesticide exposure can leave birds more susceptible to predation.
One limitation of this study is that the researchers did not quantify the chemical exposure of the birds in the different farming systems. This measurement would be helpful to better understand thresholds of tolerance and minimum exposures before impact on bird health.
Even when birds are exposed to pesticides at sublethal levels, their behavior is affected. Birds native to landscapes that exhibit high concentrations of conventional farms are less active and more susceptible to predators. By weakening birds, non-organic farms unintentionally also weaken the ecosystem services they provide, curbing the benefits that birds can provide to a farm’s consistency and yield.
Photo by: Spencer Evers; https://unsplash.com/@spencerevers