Spatial and temporal variation in lead levels related to body condition inthe Mississippi Valley Population of Canada geese

Concern over lead poisoning led to progressive prohibition of toxic shot to harvest waterfowl in the 1980's. Nevertheless, waterfowl remain susceptibl e to ingestion of lead shot because illegal use continues and spent shot pe rsists in soil and wetland substrates. While mortality due to lead toxicosi s has subsided, sublethal effects may still affect survival and reproductio n. We measured liver lead levels and body condition in 732 Canada geese (Br anta canadensis interior) during July 1984 to April 1989 in southern Illino is (USA), east-central Wisconsin (USA), and northern Ontario (Canada). Alth ough we sampled only individuals that were visibly healthy, 55 of 732 (7.5% ) geese had elevated liver lead levels (>2 ppm). Lead levels of 46 (6.3%) g eese indicated subclinical poisoning (2-6 ppm) and 9 (1.2%) geese had lead levels indicative of clinical poisoning (>6 ppm). A greater proportion of j uveniles (14.3%) had elevated lead levels than did adults (6.0%), but there was no difference between genders. Lead levels were highest in autumn and winter in southern Illinois, but were low during nesting and summer, despit e legal use of lead shot in northern Ontario during our study. Lead poisoni ng (greater than or equal to 5% of the population) was still evident during all seasons in juveniles, and during autumn and winter in adults, 5 to 10 yr after toxic shot was banned from areas where we collected geese during m igration and winter. Elevated lead levels did not affect total body mass, l ipid reserves, or mineral levels of geese we collected. Protein levels also were unaffected below 10 ppm, but there was evidence of decline at higher concentrations. Thus, it seems unlikely that lead exposure currently affect s survival or reproduction of Mississippi Valley Population (MVP) geese via body condition, although other sublethal effects cannot be discounted.