Loon Identification on Inland Lakes: Species, Field Marks, and Winter Plumage

If you are watching loons on an inland lake, the most common species you will encounter is the Common Loon. Its breeding plumage is striking: a black head and bill, a chequered black-and-white back, and a white belly. In winter, it molts to a plainer gray-brown back and white underparts. The Red-throated Loon, less frequent inland, is smaller with a slender, uptilted bill and a red throat patch in breeding season. Winter loons of both species share a similar gray-and-white pattern, so focus on bill shape and head profile to tell them apart.

Common Loon Identification: A Starting Point

Common Loon identification begins with size and shape. This bird is large and heavy-bodied, sitting low in the water with a long body and a thick, pointed bill that it often holds level. In breeding plumage, from spring through summer, the head and neck are black with a greenish sheen. The back is marked with white checkering, and the underparts are white. Look for a partial white collar or necklace pattern on the neck—two bands of white stripes that do not connect at the back. The eye is red, visible with good light or optics.

In winter, the Common Loon loses the bold pattern. Its back becomes dark gray-brown with faint pale barring, and the underparts are white. The bill changes from black to a pale gray with a dark ridge, but it remains thick and straight. The head is gray with a darker crown and a white crescent under the eye. If you see a loon in late fall or early spring, it may be in transition, showing mixed feathers.

Red-throated Loon Identification: Slender and Distinctive

Red-throated Loon identification relies on subtle differences. This species is smaller than the Common Loon, with a thinner, more delicate bill that often appears slightly uptilted. In breeding plumage, it has a gray head and neck, a dark back with faint white spots, and a distinct red throat patch that gives the bird its name. Unlike the Common Loon, the Red-throated Loon does not show a bold white checkered back.

In winter, the Red-throated Loon is very pale gray above and white below. The key field mark is the face: a white eye ring and a white line that extends up from the eye toward the back of the head. This gives the face a "spectacled" look. The bill is small and held with a slight upward tilt. Because winter plumages of loons can be confusing, practice observing the bill shape and head carriage before relying on color alone.

What Does a Loon Look Like? Body Shape and Posture

What does a loon bird look like? Beyond color, body shape is a reliable clue. Loons have a long, low profile when swimming, with their back barely above the waterline. Their legs sit far back on the body, making them powerful divers but awkward on land. A loon often rides with its bill held level or slightly raised; the Red-throated Loon tends to hold its bill pointed upward.

The head and neck are held straight when alert. The Common Loon has a larger, blockier head, while the Red-throated Loon has a rounded head and a thinner neck. In flight, loons have a hunchbacked appearance, with feet trailing behind the tail. Their wingbeats are steady and rapid, and they run along the water to take off.

What Color Is a Loon? Seasonal Changes in Plumage

What color is a loon depends on the season. In breeding plumage, the Common Loon is primarily black and white with a green sheen on the head. In winter, it becomes gray-brown on the back and white underneath. The Red-throated Loon is gray and white in breeding, with a red throat, and in winter it is pale gray above and white below. Juveniles resemble winter adults but with scaly patterning on the back.

These changes happen through molting, usually in late summer and fall. During a molt, a loon may be flightless for a few weeks while it replaces wing feathers. Seeing a loon with patches of old and new feathers is normal. If you keep field notes, record the date and any odd plumage patterns; over time you will learn the local rhythm of molt.

Winter Loon Identification: Practice on Inland Lakes

Winter loon identification is a good skill for the patient observer. On inland lakes, loons may linger into early winter before the water freezes, or they may pass through on migration. Without the bold breeding colors, you rely on structure and subtle pattern.

Use this step-by-step approach when you spot a distant loon in winter:

1. Size and shape: Is the bird large and heavy (Common) or smaller and slender (Red-throated)? Note how low it sits.
2. Bill shape: Thick and straight (Common) or thin and slightly upturned (Red-throated)? Look at the angle it is held.
3. Head and neck markings: In winter, Common Loons show a dark crown and a white crescent under the eye; Red-throated Loons show a white eye ring and a white line behind the eye.
4. Back pattern: Common Loon shows faint barring and a dark back; Red-throated Loon shows a pale, almost unmarked back with tiny white speckles.
5. Behavior: Both dive frequently, but Red-throated Loons may feed closer to shore and often tilt their bill up when surfacing.

Comparison Table: Common Loon vs. Red-throated Loon

Practical Preparation for Your Next Outing

Patient observation is the heart of loon identification. Bring binoculars with good light-gathering, because loons often stay far from shore. A spotting scope helps on larger lakes. A field notebook is useful for sketching bill shape and head profile. When you see a loon, spend a few minutes watching before reaching for your field guide: note the size, how the bird rides, and the way it dives. Common Loons glide under slowly; Red-throated Loons sometimes splash more.

Respect the bird's space. Loons are sensitive to disturbance, especially during nesting season. Stay back from known nesting areas, keep noise low, and never chase a loon for a closer look. Early morning is often the best time: calm water makes identification easier, and loons are active. Dress quietly—no rustling fabrics—and move slowly. A thermos of tea and a camp stool can turn a brief look into an hour of reward.

Why Loon Identification Matters

Learning to identify loons connects you to the health of inland lakes. Common Loons need clear water, because they hunt by sight for fish. Their presence often indicates good water quality and a healthy food web. Red-throated Loons, more coastal in winter, occasionally stop on large lakes during migration; noting them helps track seasonal movements. Your careful field notes, shared with local bird groups, can contribute to conservation. But the deeper reward is personal: knowing the difference between a Common and a Red-throated Loon is a quiet skill that deepens every hour you spend on the water.