Mercury levels were highest in adult loons breeding in Kejimkujik National Park. Because adult loons migrate to sea coasts in the winter, the birds may be accumulating mercury in their freshwater breeding areas, in their marine wintering areas, or both.
Loons accumulate mercury from the fish they eat.
Blood mercury levels were strongly correlated between adult and young loons from the same family groups. Since the young feed only on their nest lake after hatching, it appears that any mercury in them is from local fish. As the adults showed the same mercury patterns as the young, it was concluded that mercury levels in adult loons reflect local exposure to mercury in their breeding lakes, as well. A dedicated group of volunteers is on guard in Nova Scotia's Annapolis Valley. This hardy band of River Guardians actively monitor the water quality at 22 sites scattered along a 75 kilometer stretch of the Annapolis River.