The Common Loon is a large, heavy-bodied diving bird of North America’s northern lakes. In summer, adults wear a glossy black head, a red eye and a black-and-white checkered back. In winter they turn plain gray and white. Their legs sit far back on the body, which makes them powerful swimmers and awkward walkers, so they come ashore almost only to nest. It is the provincial bird of Ontario and appears on Canada’s one-dollar “loonie” coin.
Habitat
Loons breed on large, clear, freshwater lakes surrounded by forest. They need enough open water to take off, since heavy bodies and small wings require a long running start across the surface. Clear water matters because loons hunt by sight.
- Nesting: a shallow scrape right at the water’s edge, often on an island, a hummock or a muskrat lodge, so the bird can slide on and off without walking.
- Chicks: shallow, sheltered coves with small fish are used as nurseries, and chicks often ride on a parent’s back.
- Winter: most loons move to coastal ocean waters, bays and estuaries; some overwinter on large, ice-free inland lakes and reservoirs.
Range
Common Loons breed across Canada and Alaska, the northern United States (including the Great Lakes states, New England and parts of the northern Rockies), Greenland and Iceland. In winter they spread along the Atlantic coast from Newfoundland to Florida and the Gulf of Mexico, along the Pacific coast from the Aleutians to Baja California, and, for Icelandic birds, along the coasts of western Europe.
Migration patterns
Loons head north soon after the ice leaves their lakes in spring, and adults often return to the same lake, and sometimes the same territory, year after year. In fall they leave as lakes begin to freeze. Many gather in large flocks on big lakes such as the Great Lakes before moving on.
- They fly with fast, steady wingbeats, often at night as well as by day, and stop on water to rest and feed.
- Adults molt into gray winter plumage and, during the winter molt, briefly lose the ability to fly because their flight feathers drop together.
- Young loons stay on the coast for a few years before returning to inland lakes as breeders.
Diet
Loons eat mostly fish, caught in underwater pursuit. They use their feet to push, and solid bones let them dive deep and stay down for a minute or more. Typical dives are fairly shallow, though loons can go much deeper when needed.
- Freshwater: perch, sunfish, minnows, suckers, trout and other small fish.
- Also: crayfish, snails, leeches, frogs and aquatic insects, especially for chicks.
- Winter: saltwater fish and crustaceans such as herring, flounder and crabs.
- Prey is usually swallowed whole, underwater or just after surfacing.
Threats
- Lead poisoning: loons swallow lead sinkers and jigs, or fish carrying them, and lead is a leading cause of adult mortality in some regions. Switching to non-lead tackle helps directly.
- Mercury and acid rain: airborne mercury builds up in fish and in loons, reducing breeding success.
- Shoreline development and disturbance: docks, cabins and boat wakes flood or disturb nests close to the waterline.
- Fluctuating water levels: dams and rapid changes can strand or flood nests.
- Fishing line and nets: entanglement injures and drowns birds.
- Oil spills and winter die-offs: coastal spills hit wintering flocks; botulism has killed loons on the Great Lakes.
- Climate change: shifts in ice-out, water temperature and fish populations affect timing and food supply.
Easy ways to help: use lead-free tackle, keep a respectful distance from nests and chicks, slow down near shorelines, and leave natural shoreline vegetation in place.
