'Field Notes': Meeting A Montana Loon In Mexico

Feb 22, 2016

Each week the haunting wail of the common look opens Field Notes. The loon's cry always brings to my mind large, clear mountain lakes rimmed by lush coniferous forests, a handsome pair in their formal back and white courting plumage calling across the quiet water.

Large lakes because this heavy-bodied, small-winged bird requires a long runway, skittering across the water's surface to become airborne. Clean lakes, because the loon hunts visually. And quiet waters because loons abandon a nest if overly disturbed by people's activities.

So imagine my surprise when last winter, I was hanging out on a warm beach in the Sea of Cortez in Baja California, and across the water comes that plaintive cry. Loons, no doubt about it! There in the desert south, among cacti, saltwater, brown pelicans and blue-footed boobies were three common loons there for the winter. Could they have been from Montana? Possibly. We really have no idea exactly where Montana loons go in winter. Common loons are recorded as far south as Baja, California and the Gulf of Mexico. They will winter on nearly any large body of open water where there is an abundant food supply and little disturbance.

These loons had not a trace of their breeding plumage - they were in their vacation duds: informal brown. Wintering loons generally keep their individual foraging territories during the day and then congregate in loose groups, called "rafts" at night.

Winter is not an entirely easy time for loons, though. In recent years, biologists have discovered massive die-offs of loons on winter beaches - especially the Gulf of Mexico. It seems that loons pick up mercury and lead in summer waters: mercury accumulated through the food chain pollution and lead from fishing sinkers. Over time, these toxins collect in the loon's body, causing serious illness. But why large die-offs in winter? The loon's winter molt is an incredible energy drain when they must consume large amounts of food, and this stress increases the mortality of birds weakened by toxin poisoning.

To end this on a positive note, loons are still hanging on in Montana - especially because of the work of volunteers and biologists, who put up buoys near nests each spring to reduce disturbance while the loons are incubating. And now that "loony" wail makes me think of not only pristine Montana lakes, but where I'd like to spend my next winter vacation!

(Broadcast: "Fieldnotes," 01/21/15. Listen on air or online Sundays at 12:55 p.m., Tuesdays at 4:54 p.m., and Fridays at 4:54 p.m., or via podcast.)