House sparrows are heavier on organic and integrated-production farms than on conventional farms

Abstract

The negative impact of conventional farming on avian biodiversity has been increasingly documented. However, the potential effects of different farming practices on bird populations' health remain unclear. We aimed to investigate whether different farming practices (organic, integrated production, conventional/intensive) have differential effects on the body mass - as a proxy for body condition - and biomarkers of oxidative stress in house sparrows (Passer domesticus), a model species strongly associated with human activities and still abundant in Switzerland. We captured a total of 681 birds in 19 organic farms, 20 integrated-production farms (labelled “IP-Suisse”) and 18 conventional farms, and measured bird body mass and tarsus length, as well as levels of malondialdehydes (MDA, a marker of oxidative damage to lipids), superoxide dismutase (SOD, a first-line antioxidant enzyme) activity, and the ratio of oxidized over reduced glutathione (GSSG/GSH, a marker of cellular oxidative stress) in blood and sperm as biomarkers of the systemic oxidative stress endured by birds. Our findings show that house sparrows living in integrated and organic farms were 2.39 % and 4.33 % heavier than birds living in conventional farms, but we did not find any difference in tarsus length, suggesting that birds were of similar size. In addition, we did not find any difference in oxidative stress markers across farming practices. Our results highlight the potential benefits of sustainable farming practices, such as organic and integrated farming, for bird populations and emphasize the need for mitigating the negative impact of agricultural intensification on biodiversity through practices that may enhance the birds’ health and thus lead to positive population dynamics.