Common Loon

Scientific

Loons are the only members of the order Gaviiformes — an ancient lineage with no close relatives among modern birds. Gavia immer is the most widespread of the five loon species, breeding across boreal North America and Iceland and wintering along Atlantic, Pacific, and some inland coastal waters.

Anatomy. Body 28–36 inches, weight 8–12 lb. Pointed dagger-like bill. Legs set far back on the body — efficient for swimming, nearly useless on land. Solid (not pneumatic) bones reduce buoyancy for diving. Capable of dives 200+ ft and durations exceeding 90 seconds when pursuing fish.

Plumage. Striking summer pattern: black head with red eye, black-and-white checkered back, white belly. Drab gray-brown winter plumage. The summer pattern develops only in adults; first-year loons are gray.

Voice. Four signature calls — wail (long-distance contact), tremolo (alarm), yodel (territorial, only by males), and hoot (close-range communication). The wail and tremolo are the soundscape of north-woods summer for many people who recognize no other bird call.

Reproduction. 1–2 eggs per year on lakeshore nests, incubated by both parents; chicks ride on parents’ backs in the first weeks. Strong nest-site fidelity — pairs return to the same lake for 20+ years.

Pocono context

[[poconos|Pennsylvania]] has perhaps a dozen breeding pairs of common loons in any given summer, almost all on Pocono lakes:

• [[lake-wallenpaupack|Lake Wallenpaupack]] — the state’s largest reliable breeding population
• [[promised-land-state-park|Promised Land]] Lake and Lower Lake — multiple breeding territories
• [[lacawac-sanctuary|Lake Lacawac]] — protected, undeveloped; supports breeding
• [[tobyhanna-state-park|Tobyhanna]] Lake area — occasional breeding
• Smaller plateau-top lakes — historically held additional pairs, status mixed

Habitat requirements (clear water, abundant fish, undeveloped or lightly developed shoreline, low motorboat disturbance) are increasingly scarce in the eastern U.S. [[lake-wallenpaupack|Lake Wallenpaupack]] is a working test of whether a heavily-developed reservoir can still support breeding loons; current status is “yes, marginally” thanks to PPL and PA Audubon stewardship.

Threats

• Lead fishing tackle — loons swallow small lead sinkers and jigheads while ingesting pebbles for grit; lead poisoning is the leading mortality cause for adults across the species’ range. PA banned lead tackle on state-administered lakes in 2024 (after years of advocacy).
• Lakeside development — disturbance, shoreline armoring, pollution
• Motorboat traffic — wake erosion of nests; chick mortality
• Water-quality decline — fish-prey loss
• Climate change — warming summer surface temperatures push the species north

Why it matters

Common loon is the bioregion’s flagship lake species. A lake that supports breeding loons is a lake that has held its water quality, food web, and shoreline disturbance regime against considerable pressure. [[directory|The directory]]‘s directional intent on water-quality stewardship is concretely measurable through whether the loons keep coming back.

See also

Auto-generated from this entry’s typed relations: frontmatter, grouped by relation type so the editorial signal isn’t flattened.

• Substrate of: [[pocono-plateau]]
• Member of: [[animal]]
• Contained by: [[poconos]] · [[lacawac-sanctuary]]

Sources

• PA Game Commission bird species accounts
• The Birds of North America — Gavia immer species account
• [[lake-wallenpaupack|Lake Wallenpaupack]] Watershed Management Foundation, breeding-loon monitoring reports
• Audubon [[poconos|Pennsylvania]] state-of-the-loons reports