Lead poisoning and other mortality factors in trumpeter swans

Abstract

AbstractLead poisoning and other causes of mortality of trumpeter swans were investigated. Necropsies or Pb concentrations in livers were available for 72 trumpeter swans (Cygnus buccinator) found dead in seven western states from 1976 to 1987; data from other published and unpublished sources (1925 to 1987) also are summarized. Ingestion of lead artifacts (shotgun pellets or fishing sinkers) accounted for about 20% of the known mortality of trumpeter swans in the tri‐state area of Idaho, Montana and Wyoming, where the population has been declining for several decades. In western Washington, the incidence of lead‐induced mortality was higher and accounted for nearly 50% of the known mortalities. Maximum Pb concentrations (wet weight) in the livers of birds found dead and in whole blood from captured swans were 37 and 0.71 μg/g, respectively. Other elements, including Cd, Cu and Zn, were generally not elevated in blood and tissue samples. It is not certain that lead toxicosis is related to the decline of the tri‐state swan population. Other causes of mortality in swans include gunshot, disease and traumatic injuries (impact).