Common Mergansers are commonly mistaken for adult loons in breeding plumage, however a few key traits differentiate the species.
- Bill color: The Common Loon in its breeding plumage has a black bill. A male Common Merganser has a red bill.
- Head color: The Common Loon has an iridescent black head. The male Common Merganser has a green head.
- Body color: The Common Loon has a black and white checkered back. The male Common Merganser has black and white plumage but has bright white sides.
Juvenile loons (chicks older than 8-weeks) and immature loons (2nd year birds that occasionally summer on lakes) may be mistaken for female common mergansers. The following characteristics can help to distinguish between the two:
- Bill color: Juvenile and immature loons have gray or grayish-white bills. Female Common Mergansers have red bills.
- Head color: Juvenile and immature loons have gray heads. Female Common Mergansers have reddish-brown crested heads.
- Body color: Juvenile and immature loons have gray plumage that with a distinct white scalloped pattern. Female Common Mergansers have gray plumage with no such scalloping.
Another diving, fish-eating bird that is sometimes mistaken for a loon is the Double-crested Cormorant. Characteristics that help to differentiate between Double-crested Cormorants and Common Loons include:
Body and head shape: Double-crested Cormorants have slender bodies with a long neck. Common loons have larger bodies with a shorter, thicker neck and head.
Bill shape and color: The bill of the Common Loon is long, black, and pointed. Its shape is best described as “dagger like.” The bill of the Double Crested Cormorant is hooked and is yellow with an orange patch of the base.
Behavior: Double-crested Cormorants are often seen standing on docks, rocks, or buoys with wings outstretched to dry. Common Loons are not able to stand upright and only go on land to nest or if they are sick or injured.
Common Mergansers have up to 17 ducklings who are sometimes seen riding on the female’s back, but they are lighter in color than loon chicks and have a reddish crown. Common Loons have 1-2 chicks. Loon chicks change in color from almost black to light brown to grey as they grow. Scroll to the bottom of the page to see the loon chick stages. Merganser broods can be reduced to 2 chicks or fewer due to predation.