Loons are listed first in most standard field guides and a quick glance at the entry on the common loon shows that the bold black and white breeding feathers observed in northern birds are replaced by drabber hues when the birds migrate south. While in Florida, both male and female winter loons have a white underside and a gray-brown head, neck and back. In late spring along the Gulf Coast and in north Florida lakes, a few birds acquire breeding plumage just prior to their migration north.
Common loons are heavy-bodied birds that sit low in the water just offshore. They are known as the great northern diver by British birders and for good reason. They dip their heads below the surface to visually locate prey and then power through the water with large webbed feet.
The common loon, with its exquisite breeding plumage and yodel-like call, has come to symbolize wilderness and northern lakes to many people. But once the breeding season ends in Alaska, Canada and the northern U.S., loons head south to winter along the Atlantic and Gulf coasts. Thousands of loons dot the bays and open oceans surrounding Florida and are a very visible part of the winter coastal landscape.
Streamlined and efficient underwater swimmers, loons can quickly move in on small fish, crabs and invertebrates, usually swallowing them while still submerged. Most dives are shallow and last less than a minute, but deep dives may last up to five minutes. Loons are adapted to life on the water; their legs are located so far back on their bodies that they are one of the few birds that cannot walk on land. Instead they must crawl or push their bodies onto land or into their nests.
The loon call, described as a maniacal musical laugh, a falsetto wail, a yodel and a tremolo, is commonly heard during the breeding season. Loons are mostly quiet during the winter in Florida, though they occasionally call in late morning or early evening just before spring migration.
In the north, loons are most vulnerable to mercury contamination in acid lakes, while oil spills in coastal waters affect the wintering birds. Habitat loss, human disturbance and mortality related to lead poisoning and commercial fish nets also stress the population.