09/04/2026
Happy Loon Fact Friday!
Loons go through a complex molting cycle each year. Between around August through November, adults molt from their breeding plumage, the black and white, into their winter plumage, which is mostly gray and brown. This can make it difficult to tell adult loons apart from juveniles. Juveniles also have gray and brown plumage and will usually stay this color until they reach breeding age at 3 years old.
Molting can begin as early as late July for adults that are not raising chicks. The molt will start around the base of the bill and cheeks before moving backward down the body. By October, many loons are deep in their molt, while some may still have breeding plumage into November. One of the most important parts of the molt is the loss of flight feathers, which typically occurs in late winter or early spring on the wintering grounds. Because loons are heavy birds, losing even a few flight feathers can leave them unable to fly, and so loons molt all of their flight feathers at once in a “catastrophic molt” to reduce the amount of time they are flightless. It is thought that loons evolved to molt their flight feathers in late winter or early spring because they historically did not have enough time to complete a molt between the end of the breeding season and the freezing of lakes in the fall. Lakes are freezing over later than they used to due to human-caused climate change, allowing some loons to stay on the breeding grounds later into the year. If these loons molt their flight feathers and get caught in a deep freeze, they can be “iced-in” and trapped during this flightless period.
Photo by Ken Rohling
To learn more go to adkloon.org
