This study was designed to determine if night-herons nesting at Ruby Lake, Nevada, shared a common wintering area with lesser contaminated night-herons nesting farther north in Oregon and Idaho. Radiotelemetry (29 transmitters) and banding studies indicated that the lesser-contaminated Oregon-Idaho night-herons wintered primarily in coastal Mexico (mean 22-23'N latitude), while the Ruby Lake night-herons wintered in the southwestern United States with some in the interior of northern Mexico (mean 29-30?N latitude). We believe the nearly disjunct wintering areas for the populations, and the apparent differing pollutant loads on the wintering areas accounted for the 3-fold higher DDE egg residues at Ruby Lake. Findings from this study emphasize the influence migration patterns can have on pollutants accumulated by populations of migratory birds nesting in relatively unpolluted areas and at relatively short distances apart (400 km).
Additional publication details
Radiotelemetry locates wintering grounds of DDE-contaminated black-crowned night-herons