Assessment of the impact of oil and gas industry emissions on the European Starling (Sturnus vulgaris)
Irvine, Michelle Dawn
The size of the environmental footprint of the oil and gas industry in western Canada is enormous, yet the potential impact of the industry and related chemical emissions on local environments remains largely unknown. Therefore, when a study was initiated to investigate the health, productivity, and immune competence of domestic livestock chronically exposed to emissions from oil and gas batteries and associated field facilities in the western provinces of Canada, a parallel study of a representative wildlife species was conducted to gain further insight into the potential impact of the industry on environmental health. To this end, wild European Starlings (Sturnus vulgaris) were attracted to nesting locations surrounding oil and gas emission sites and suitable reference sites through strategic placement of nest boxes in the breeding seasons of 2001 and 2002. Spanning these two field seasons, reproductive performance (clutch size, egg weight and volume, and hatchability), nestling condition and survival were examined in 120 nests over a large geographical area in central Alberta. In addition, hepatic ethoxyresorufin-odeethylase (EROD) activity (a measure of cytochrome P450IA1 biotransformation activity) and concentrations of polycyclic aromatic hydrocarbon (PAH) metabolites in bile were measured as biomarkers of exposure to certain contaminants, including PAHs, present in oil and gas emissions. Hatchability and fledging success of the starlings were not significantly associated with SO2, H2S, and benzene concentrations, and proximity to oil and gas well sites. In contrast, ambient weather conditions, particularly total precipitation and average temperature during the period of interest, were significantly associated with these outcomes. Nestling size, when measured as tarsal length, was significantly decreased with exposure to increasing benzene concentration. However this effect was not seen on nestling development, measured using the length of the 10th primary feather. None of nestling weight, egg weight or egg volume was associated with any measurement of contaminant exposure. Although no association was found between EROD activity or biliary PAH metabolite concentrations in starling nestlings and the exposure variables measured, nest occupancy rate (an effect of nest location on the outcome variable), and minimum temperature during the period from nest initiation to fledging of the brood acted as predictors of EROD activity, while total precipitation was associated with PAH metabolite residues in nestlings in 2001. Studies such as this one of wildlife populations may enhance our insight into potential toxicological mechanisms associated with exposure to oil and gas industry emissions, and lead to the identification of specific indicators of that could be applied in future research.