The Common Loon in summer is very striking with its black-and-white checkered back, glossy black head, white belly and wing lining, and characteristic white necklace around the throat. All loons have greyish feathers in the winter, and immature birds tend to resemble adult birds in winter plumage. The white feathers of the belly and wing linings are present year-round. Loons’ habit of swimming low in the water helps to distinguish them from other waterbirds, such as ducks and geese. Loons most resemble the grebes, but can be identified by their larger size, thicker necks, and longer bills. In flight, loons can be recognized by their humpbacked profile, with head and neck held low and feet pressed back towards the body and projecting beyond the tail. Males and females look the same, although males are generally larger. Adults are large-bodied, weighing from 2.7 to over 6.3 kg and measuring almost a metre from bill tip to outstretched feet. The bill is quite large, averaging 75 mm in length, and is black in colour throughout the year.