. The Canadian field-naturalist. 40 60 Number of swans Figure 2. Cause of death in reported Trumpeter Swans mortalities in British Columbia, 1976-1994 (N=186). A detailed description of the diagnostic categories is provided in the Methods Section. were from the lower Fraser valley and Vancouver Island (Figure 1). Of the 186 swans collected, 47% (87/186) were diagnosed as lead-poisoned (Figure 2). The majority of lead-poisoned swans were from the Lower Fraser Valley and southern Vancouver Island (83/87, 95%). Of the 44 swans collected out- side the south-western coast of British Columbia, the o
. The Canadian field-naturalist. 40 60 Number of swans Figure 2. Cause of death in reported Trumpeter Swans mortalities in British Columbia, 1976-1994 (N=186). A detailed description of the diagnostic categories is provided in the Methods Section. were from the lower Fraser valley and Vancouver Island (Figure 1). Of the 186 swans collected, 47% (87/186) were diagnosed as lead-poisoned (Figure 2). The majority of lead-poisoned swans were from the Lower Fraser Valley and southern Vancouver Island (83/87, 95%). Of the 44 swans collected out- side the south-western coast of British Columbia, the only four classified as lead-poisoned were found along the northern coast at Tlell River (53° 36'N, 131° 56'W), and Hunter Island (51° 57'N, 128° OO'W), and at Vanderhoof (54° 01'N, 124° Ol'W). All lead-poisoned birds were found between November and May. Of the lead-poisoned birds which were aged and/or sexed, 71% (32/45) were adults and 58% (25/43) were females. Temporal trends in the incidence of lead poisoning were not observed (Figure 3). Of 102 swans analyzed for lead; 65 (64%) were classified as lead-poisoned and one (1%) was sub- clinically exposed. Lead residues were measured in kidney of 75 Trumpeter Swans; 46 were classified as lead-poisoned, with a mean of mg/g (SD , range mg/g) (Table 1). Of the 75 swan livers analyzed for lead, 38 had levels diagnostic of lead poisoning, with a mean of mg/g (SD , range 10-121 mg/g). When both were measured in the same bird, equal or higher lead levels were detected in kidney compared to liver tissues in the majority of the cases (55/62, 89%). Blood lead levels were deter- mined in 20 swans, of which 14 had lead concentra- tions indicative of lead poisoning (mean , SD , range mg/g). Seven of the 10 bone samples analyzed for lead had concentrations > 2 mg/g, the threshold value indicative of sub-lethal exposure (mean , SD , range mg/g). Lead shot were detected in gizzar
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