Plasma Cholinesterase Activity in Wild Birds from Undisturbed Woodlands in the Central Monte Desert

Plasma cholinesterase activity is a biomarker sensitive to the effect of organophosphate and carbamate pesticides, and its enzymatic levels have been previously unknown for most of the wild birds analyzed in the present study. Our objectives were to establish plasma acetylcholinesterase levels in songbirds of 2 undisturbed sites in the central Monte Desert (Argentina). We also examined the influence on cholinesterase activity of age, sex, body condition, feeding and migratory habits, and species. One hundred and sixty-five wild birds belonging to 26 species were studied. The values obtained for acetylcholinesterase activity provide a good estimate of the normal values in free-living individuals of the species Zonotrichia capensis, Molothrus bonariensis, Passer domesticus, Diuca diuca, Poospiza ornata, Saltator aurantiirostris, Gryseotyrannus aurantioatrocristatus, and Columbina picui, with interspecies differences. The median enzymatic levels ± standard error of the mean ranged from 546.31 ± 17.97 μmol min^-1 L^-1 in P. domesticus to 3439.90 ± 173.92 μmol min^-1 L^-1 in Tyrannus melancholicus. No significant differences were detected between different sexes or ages. Birds that migrate (which are also insectivores) showed higher levels of cholinesterase than residents (mainly granivores). It is recommended that in cases of bird poisoning, plasma cholinesterase activity can be used as a diagnostic tool only if pre-exposure levels obtained in the same species are available, and ideally evaluated in individuals from the same biogeographical region. Environ Toxicol Chem 2019;38:1692-1700. © 2019 SETAC.