Morphological Characteristics

Loons, also called “divers,” have distinctive breeding and winter plumages, which can make identification difficult.  They have small wings (and thus high wing loading), short legs, and heavy bodies with webbed feet that are set back.  They have pointed bills that are used to catch fish while diving.  Summer plumages are brightly colored and patterned, and loons swim very low in the water.   Males and females have identical plumages, but males are larger on average

Loons were classified in the same order as grebes (collectively known as Colymbiformes) until the 1930s, when it was determined that morphological similarities were due to convergent evolution instead of common ancestry.  Grebes were moved to Podicipediformes, while loons went to Gaviiformes.

Common loon in flight.

Red-throated loon swimming low in the water.

Common loon diving.

Webbed foot of common loon.

Baby common loon on mother's back.

Sources:

• Alderfer, Jonathan.  2006. Complete Birds of North America, pp. 58-61. National Geographic, Washington, D.C.
• Peterson, Roger Tory.  2010. Peterson Field Guide to Birds of Eastern and Central North America, 6^th Edition, pp. 58-59. Houghton Mifflin Harcourt, Boston and New York.