Temporal biomarker responses in wild passerine birds exposed to pesticide spray drift

A field study was conducted to assess the degree of exposure experienced by nestling and adult great tits, (Parus major) to spray drift of pirimicarb and dimethoate. Nondestructive assays of serum esterases, serum butyrylcholinesterase (BChE), and carboxylesterase (CbE) were used as exposure biomarkers and measurements of weight gain and survival were made to assess adverse biological effects. Nest boxes were placed in hedgerows bordering fields sprayed with pesticides (either pirimicarb or dimethoate). One hedge was sprayed directly with pirimicarb to simulate maximum drift effect. Two hedges were left untreated to serve as control areas. The concentrations of the two insecticides were within the recommended dose for cereals. Significant inhibition of BChE activity was detected within 24 h in adult birds exposed to drift of dimethoate and in adult birds from the hedge sprayed directly with pirimicarb. Highly significant correlations were found between the weight of unexposed nestlings and BChE and CbE activity, indicating that a developmental increase in enzyme activities is correlated with the growth rate of the nestlings. Inhibition in nestling BChE activity was found in all treated hedges after 24 h. A tendency of reduced weight gain was found in nestlings both between 0 to 24 h and 24 to 48 h after treatment in all the treated hedges compared to nestlings from the control hedge (p > 0.07). These results indicate the potential of pesticide drift to reduce growth rate and survival of juvenile wild passerine birds