Reproductive success and contaminants in tree swallows (Tachycineta bicolor) breeding at a wastewater treatment plant

The uptake and effects of contaminants were measured in the insectivorous tree swallow (Tachycineta bicolor) at a wastewater treatment site. The study examined reproductive, immunological, and growth endpoints in tree swallows exposed to chlorinated hydrocarbon contaminants and to 4-nonylphenol in wastewater lagoons at the Iona Wastewater Treatment Plant, Vancouver (BC, Canada). Clutch size was significantly lower in tree swallows breeding at Iona Island in 2000 and 2001 compared to the reference site. In 2000, fledging success was significantly lower and mean mass of nestling livers was significantly higher in the tree swallows breeding at the Iona Island Wastewater Treatment Plant. Additional factors that may influence reproductive success, such as parental provisioning and diet composition, did not differ significantly between sites. Levels of 4-nonylphenol detected in sediment and insects were elevated at the Iona Island Wastewater Treatment Plant (2000: lagoon sediment 82,000 ng/g dry wt, insects 310 ng/g wet wt; 2001: lagoon sediment 383,900 ng/g dry wt, insects 156 ng/g wet wt) compared to the reference site (2000: pond sediment 1,100 ng/g dry wt, insects not sampled; 2001: pond sediment 642 ng/g dry wt, insects 98 ng/g wet wt). These results indicate that tree swallows might be a useful indicator species for exposure to 4-nonylphenol at wastewater treatment sites; however, further work is necessary to determine the extent of uptake and effects of 4-nonylphenol in riparian insectivorous birds.