Lead concentrations and reproductive success in European starlings Sturnus vulgaris nesting within highway roadside verges

Abstract

In 1981, we studied lead concentrations and reproductive success in freeliving European starlings Sturnus vulgaris nesting within the verges of two Maryland highways with different traffic volumes, Route 197 (average daily traffic volume [ADT] = 10 800 vehicles) and the Baltimore-Washington Parkway (ADT = 52 500 vehicles) and a nearby control area. Concentrations (mgkg⁻¹ dry weight) of lead in the ingesta (84–94 mg kg⁻¹), carcasses (4·0–9·6 mgkg⁻¹) and feathers (6·8–52 mgkg⁻¹) of Parkway nestlings and adults were 3 to 13 times those found in starlings from the control area, whereas lead concentrations in the ingesta and tissues of starlings from the verge of Route 197 were similar to those of controls. Activity of δ-aminolevulinic acid dehydratase (ALAD) in red blood cells (RBCs) of adult and nestling starling from the Parkway was depressed from 43 to 60% compared to controls. RBC ALAD activity in adults from nests along Route 197 was similar to that of adult starlings from the control area, but that of their young was depressed 17%. Haemoglobin concentrations (−16%) and haematocrits (−10%) in Parkway nestlings were depressed compared with those of nestlings from the other two study areas, whereas those of adults were not affected. Clutch size, number of young hatched and the number of young in nests 1 to 3 days before fledging were similar among sites, as were body weights of adults and prefledging weights of their young. However, brain weights of Parkway nestlings were lower (P<0·05) than those of nestlings from the other study areas. Results suggest that lead within verges of major highways probably does not pose a serious hazard to adult ground-foraging songbirds. However, the effects of lead-induced reductions in haemoglobin concentration, haemotocrit, RBC ALAD activity and brain weight on the postfledging survival of their young are not known.