|Common Loons on Middle Pond near Saranac Inn © Dave Spier|
Loons are large birds. They measure 32 inches in length and have a wing span of nearly four feet. Males are larger than females. From March through October, the adults sport high-contrast black and white plumage. The heads and beaks are black, their necks have white or gray bands, the breast and belly are white, the sides black and the back is extensively checkered. The only color is in the red eyes. Juvenile loons, and adults in winter plumage, are overall gray or dark gray with white on the throat and upper breast. They may have a faint, light gray, partial band around the neck.
On the water, loons ride low like a submarine, an appropriate metaphor because they dive to catch their food. A number of adaptations help them do this. Their feet are far to the rear and to the sides to facilitate paddling underwater and their marrow-filled bones are thicker than other birds. For this reason, loons are heavy birds that require a long stretch of open water to get a running start to become airborne. Once in flight, their thick necks are balanced by large feet trailing to the rear. The relatively small wings make diving easier, but flying is more laborious. The location of the feet at the rear makes it nearly impossible for loons to walk on land, so they nest on the edge of islands where they can just slip into the water if danger approaches.
Loons face a number of manmade threats. Air pollution from mid-western power plants and auto emissions contains sulfuric and nitric acids and mercury. These are carried eastward by prevailing winds and fall as acid rain, in turn killing many of the small fish and organisms that loons depend on for food. Chicks can starve to death before four weeks of age. Acidic water also converts mercury to an organic form that enters the food chain and becomes concentrated in loons at the top of the ladder. This methyl mercury attacks the bird's nervous system, interfering with its ability to catch fish. In high enough concentrations, the birds die from mercury poisoning.
Loons also become entangled in discarded fishing line and die of lead poisoning after they ingest old fishing sinkers which are mistakenly picked up from the bottom along with the small stones used to grind up food in their gizzards. These hazards also afflict a host of other waterbird species. Shoreline development and increased recreational use of northern lakes pose additional threats to loons as they lose traditional nesting sites and face increased boat and jetski traffic.
|Adult Common Loon with juvenile on Middle Pond © Dave Spier|
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