Field evaluation of lead effects on Canada geese and mallards in the Coeurd'Alene River Basin, Idaho

Hatch year (HY) mallards (Anas platyrhynchos) in the Coeur d'Alene (CDA) Ri ver Basin had higher concentrations of lead in their blood than HY Western Canada geese (Branta canadensis moffitti) (geometric means 0.98 versus 0.28 mu g/g, wet weight). The pattern for adults of both species was similar, a lthough geometric means (1.77 versus 0.41 mu g/g) were higher than in HY bi rds. HY mallards captured in the CDA River Basin in 1987 contained signific antly lower lead concentrations in their blood than in 1994-95 (0.36 versus 0.98 mu g/g); however, some very young mallards were sampled in 1987, and concentrations in adults were not significantly different in 1987, 1994, or 1995 (1.52, 2.07, 1.55 mu g/g, respectively). Both species in the CDA Rive r Basin in 1994-95 showed significantly reduced red blood cell delta-aminol evulinic acid dehydratase (ALAD) activity compared to the reference areas: Canada geese (HY -65.4 to -86.0%, adults -82.3%), and mallards (HY -90.7 to -95.5%, adults -94.1%). Canada goose goslings were divided into size class es, and the two smaller classes from the CDA River Basin had significantly elevated free erythrocyte protoporphyrin (protoporphyrin) levels compared t o the reference area (15.2x and 6.9x). HY and adult mallards both had signi ficantly elevated protoporphyrin (5.9x and 7.5x). Recognizing that interspe cific differences exist in response and sensitivity to lead, it appears (at least for hemoglobin and hematocrit) that Canada geese were more sensitive to lead than mallards, i.e., adverse hematologic effects occur at lower bl ood lead concentrations. Only Canada geese from the CDA River Basin, in spi te of lower blood lead concentrations, had significantly reduced mean hemog lobin and hematocrit values. No euthanized Canada geese (all HYs) from CDA River Basin were classified as clinically lead poisoned, but 38 Canada gees e found dead in the CDA River Basin during a concurrent study succumbed to lead poisoning between 1992 and 1997. Only 6 (15.8%) of these 38 contained ingested lead shot, which contrasts greatly with the 75-94% incidence of in gested lead shot when mortality was due to lead shot ingestion. Lead from o ther contaminated sources (i.e., sediments and vegetation) in the CDA River Basin was strongly implicated in most Canada goose deaths. Based on the 31 live mallards and Canada geese collected in the CDA River Basin, which wer e representative of the live populations blood sampled only, the prevalence of subclinical and clinical lead poisoning las determined by liver lead co ncentrations, excluding birds with ingested lead shot) was higher in mallar ds: subclinical (4 of 8, 50% HYs and 6 of 11, 55% adults); clinical (0% HYs and 4 of 11, 36% adults), with less data available for Canada geese (only 1 of 9, 11% HYs marginally subclinical). The clinically lead-poisoned malla rds had extremely high concentrations of lead in blood (2.69-8.82 mu g/g) a nd liver (6.39-17.89 mu g/g). Eight mallards found dead in the CDA River Ba sin during a concurrent study were diagnosed as lead poisoned, and only one (12.5%) contained ingested lead shot, which again strongly implicates othe r lead sources. The finding of dead lead poisoned Canada geese together wit h the high percentage of live mallards classified as subclinically or clini cally lead poisoned, in combination with the low incidence of ingested lead shot causes us concern for both of these species, which live in associatio n with lead-contaminated sediment in the CDA River Basin.