Where Do Loons Go in Winter? Coastal Winters and Molt

Why loons must leave their lakes

The common loon is a diving bird that hunts fish by sight and needs open water to feed. It also needs a long stretch of open water to take off. When northern lakes freeze, a loon that stays too long can be trapped on a shrinking patch of water with no way to fly out. So nearly all loons migrate before the ice forms.

Adults usually leave their breeding lakes between September and November. Many gather first on large lakes, where they feed and rest in loose groups before heading on. Juveniles stay behind for several weeks after their parents and then make their first migration alone, guided by instinct rather than following adults.

Where do North American loons spend the winter?

Loons generally fly to the nearest large body of water that does not freeze. Studies with satellite transmitters and banding show broad patterns:

Some of the highest winter concentrations are along the coasts of South Carolina, the Florida Panhandle and from Massachusetts to Maine. Smaller numbers winter on large inland lakes and reservoirs across the United States wherever the water stays open.

Loons migrate mostly by day, flying alone or in loose groups, often high above the ground at around 1,500–2,700 m (4,900–8,900 ft). Many stop to rest and feed on the Great Lakes and other big lakes on the way. In flight they are fast, reaching speeds of up to about 120 km/h (75 mph).

Where do great northern divers winter in Europe?

In Europe the same species is called the great northern diver. Most of Europe’s breeding birds nest in Iceland, with a few in Greenland and Svalbard. In winter, several thousand great northern divers spread along the Atlantic coasts of western Europe, probably coming from Iceland, Greenland and northeastern Canada.

The United Kingdom is one of the most important wintering areas, with roughly 3,500–4,500 birds, especially around Scotland’s islands and sea lochs and the coasts of southwest England. Others winter around Ireland and along the coasts of Norway, France and northern Spain, and a few hundred reach Portugal and the western Mediterranean. Some Icelandic birds stay in Iceland all year.

How loons change in winter

Winter loons look like a different bird. In autumn adults molt their striking black-and-white breeding feathers and become gray-brown above and white below, with a pale throat and a paler, grayish bill. The red eye stays. This plain plumage is worn from about October until late winter.

Life on the ocean is also different. Loons feed on marine fish and crustaceans such as herring, flounder, rockfish, crabs and shrimps. They are mostly silent, so the wild calls of summer are rarely heard on the coast. To hear what you are missing, see what does a loon sound like?.

The flightless molt at sea

Late winter brings the hardest part of the year. Between about January and March, adult loons shed all their flight feathers at the same time, like ducks and geese do. For several weeks they cannot fly at all and live entirely on the water, diving to escape danger.

Molting all at once is risky, but it gets the job over quickly. The new feathers grow in just in time for spring migration, and at the same time the birds molt their body feathers back into breeding plumage. Second-year birds follow a different schedule and molt their flight feathers in summer instead.

The return north in spring

Loons head back north in spring and arrive on their lakes as soon as the ice breaks up, sometimes within a day or two of ice-out. Males usually arrive first, often a few days to a few weeks ahead of females, and reclaim their territories. Pairs do not winter together, so they meet again on the breeding lake.

Young loons behave differently. They usually spend their first two years or so on the ocean, then begin returning north as subadults and visiting lakes before they are old enough to breed, typically at around 6 years old.

Threats on the wintering grounds

Winter is a risky season for loons. On the coast they face oil spills, entanglement in fishing nets, pollution and outbreaks of disease such as botulism. Bad storms during migration can also force loons down onto land, where they cannot take off again, as explained in why can’t loons walk?.

To learn more about why so many birds make long seasonal journeys like this, read why do birds migrate?.