Lead exposure in passerines inhabiting lead-contaminated floodplains in the Coeur d'Alene River Basin, Idaho, USA

Blood collected from song sparrows (Melospiza melodia) and American robins (Turdus migratorius) captured with mist nets in a lead-contaminated (assess ment) area and nearby uncontaminated (reference) areas within the Coeur d'A lene Basin in northern Idaho was analyzed for delta-aminolevulinic acid deh ydratase activity (ALAD) and hematocrit levels, and livers were analyzed fo r lead. Mean ALAD inhibition in the assessment area was 51% in song sparrow s and 75% in American robins, The proportion of the sampled population with ALAD inhibition >50% was calculated to be 43% for song sparrows and 83% fo r American robins. Assessment area hematocrit values for song sparrows ((x) over bar = 39.9) and American robins ((x) over bar = 39.5) were lower than in reference areas ((x) over bar = 42.4 for song sparrows and 40.2 for Ame rican robins); however, differences were not statistically significant (p > 0.05). Significantly higher levels of lead (wet weight) were found in live rs from song sparrows captured on the assessment area ((x) over bar = 1.93 ppm) than on reference areas ((x) over bar = 0.10 ppm) (p = 0.0079). Study results indicate that 43% (95% confidence interval [CI] = 12.9-77.5%) of th e song sparrows and 83% (95% CI = 41.8-99.2%) of the American robins inhabi ting the floodplain along the Coeur d'Alene River in-the assessment area ar e being exposed to lead at levels sufficient to inhibit ALAD by > 50%. Vari ability in lead exposure indicators was attributed to high variability in e nvironmental lead concentrations in the Coeur d'Alene River Basin.