Agricultural pesticides and ectoparasites: potential combined effects on the physiology of a declining aerial insectivore. Issue 1 (28th April 2021)

• Record Type: Journal Article
• Authors: Sigouin, Audrey; Bélisle, Marc; Garant, Dany; Pelletier, Fanie
• Editors: Cooke, Steven
• Is Part Of: Conservation physiology. Volume 9:Issue 1(2021)
• Publication Date: 2021-04-28
• Subjects: Ecotoxicology -- ectoparasites -- farmlands -- pesticides -- Protocalliphora sp -- tree swallow; Nature -- Effect of human beings on -- Periodicals; Conservation biology -- Periodicals; 577.05
• DOI: 10.1093/conphys/coab025
• Languages: English
• ISSNs: 2051-1434

Abstract

Abstract : In this study, we investigated whether exposure to pesticides and ectoparasites led to combined effects on tree swallow ( Tachycineta bicolor ) nestling physiology in an agricultural landscape. Our results show that haematocrit, but not bacteria-killing ability or leucocyte counts, was negatively affected by the combined exposure to these two stressors. Abstract: Agricultural pesticides usage has been increasing globally. These compounds have been developed to disrupt pest species physiology, but because their specificity is limited, they can also have adverse effects on non-target organisms. Recent studies have shown that the damaging toxicological effects of pesticides can be amplified in stressful environments. However, few studies have documented these effects in natural settings where organisms are simultaneously exposed to pesticides and to other environmental stressors such as parasites. In this study, we assessed both pesticide and ectoparasite effects on the physiology of a free-ranging bird. We measured physiological markers including haematocrit, bacteria-killing ability (BKA) and leucocyte counts, as well as exposure to haematophagous Protocalliphora larvae, in tree swallow nestlings ( Tachycineta bicolor ), a declining aerial insectivore, in southern Québec, Canada, for over 3 years. We found that combined exposure to pesticides and Protocalliphora larvae was negatively related to haematocrit, suggesting possible synergistic effects. However, we found no such relationships with BKA and leucocyte counts, highlighting the complexity of physiological responses to multiple stressors in natural settings. Populations of several aerial insectivores are declining, and although sublethal pesticide effects on physiology are suspected, our results suggest that exposure to other factors, such as parasitism, should also be considered to fully assess these effects, especially because pesticides are increasingly present in the environment.