Dynamics of Low-Level Organochlorines in Adult Cackling Geese over the Annual Cycle

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Abstract
To study patterns of acquisition of pollutants during migration, organochlorines in cackling Canada geese (B. canadensis minima) over the annual cycle from 1973-1974 were monitored. This annual cycle is characterized by a mostly uncontaminated breeding area (Alaska''s Yukon-Kuskokwim river deltas [polychlorinated biphenyls]), but mostly diffuse, contaminated nonpoint sources on the southern migration routes and wintering areas (the Klamath Basin of Oregon and California and California''s Central Valley). Levels of all organochlorine (OC) compounds detected were in the ppb (ng/g) range and not believed to be of overt detrimental concentrations. Changes in total residue body-burdens followed patterns that could be related to reported OC use only on a qualitative basis. Residue variation was partly due to seasonal physiological changes and pharmacodynamic characteristics of the OC compounds detected, but most variation was still probably the result of variations in exposure (estimated by residue body-burdens). Variations in the patterns of gain suggest slightly different exposures to different compounds during migration and wintering, although all residues rapidly increased during this phase of the annual cycle. Over most of the annual cycle both sexes retained similar residue levels. Concentrations of toxaphene, the most-used organochlorine insecticide in California during this study, were below detection limits. Occurrence of several banned compounds may indicate their illegal uses in some areas. Estimated persistences of the OC residues (in relation to PCB [polychlorinated biphenyls]) were as follows: very low-endrin; low-DDT + DDD, dieldrin, and chlordane/heptachlor metabolites; moderate-DDE; high-PCB. At present contamination levels, cackling geese should eliminate all these residues but PCB and DDE annually.