New York Natural Heritage Program
Common Loon
Gavia immer (Brunnich, 1764)
Birds

Habitat [-]
Common Loons breed on a wide variety of lakes and reservoirs in the Adirondacks ranging from oligotrophic (low-nutrient) to eutrophic (high-nutrient), small to large, shallow to deep, clear to turbid, and remote to heavily developed (Rimmer 1992). Breeding has been documented on lakes as small as 4 ha, but loons typically nest on lakes 20 ha or larger (McIntyre 1975). Lakes smaller than 80 ha often support only a single pair (McIntyre 1988). Common Loons often breed on lakes that contain both shallow and deep water areas. Shallow areas are important for feeding and brood rearing, and deeper areas provide escape cover for incubating adults. Nests are often located as close as possible to deep water, on the edge of an island or low hummock, or on rocks, logs, or pieces of bog mat (McIntyre 1988). Since loons are visual feeders, water clarity is also an important component of breeding habitat selection (McIntyre 1975, McIntyre 1988). Nonbreeding habitat is primarily seacoasts, bays, inlets, and estuaries, less frequently along lakes and rivers, and occasionally up to 100 km off the coast (AOU 1998).

Associated Ecological Communities [-]
  • Bog lake
    The aquatic community of a lake that typically occurs in a small, shallow basin (e.g., a kettehole) that is protected from wind and is poorly drained. These lakes occur in areas with non-calcareous bedrock or glacial till; many are fringed or surrounded by a floating mat of vegetation.
  • Eutrophic dimictic lake
    The aquatic community of a nutrient-rich lake that occurs in a broad, shallow basin. These lakes are dimictic: they have two periods of mixing or turnover (spring and fall); they are thermally stratified in the summer, and they freeze over and become inversely stratified in the winter.
  • Meromictic lake
    The aquatic community of a relatively deep lake with small surface area that is so protected from wind-stirring that it has no annual periods of complete mixing, and remains chemically stratified throughout the year. These lakes may be protected from mixing by a sheltered surrounding landscape (e.g., a deep basin) or by adjacent tree cover.
  • Mesotrophic dimictic lake
    The aquatic community of a lake that is intermediate between an oligotrophic lake and a eutrophic lake. These lakes are dimictic: they have two periods of mixing or turnover (spring and fall); they are thermally stratified in the summer, and they freeze over and become inversely stratified in the winter.
  • Oligotrophic dimictic lake
    The aquatic community of a nutrient-poor lake that typically occurs in a deep, steeply-banked basin. These lakes are dimictic: they have two periods of mixing or turnover (spring and fall), they are thermally stratified in the summer, and they freeze over and become inversely stratified in the winter.
  • Oligotrophic pond
    The aquatic community of a small, shallow, nutrient-poor pond. The water is very clear, and the bottom is usually sandy or rocky.
  • Summer-stratified monomictic lake
    The aquatic community of a lake that is so deep (or large) that it has only one period of mixing or turnover each year (monomictic), and one period of stratification. These lakes generally do not freeze over in winter (except in unusually cold years) or form only a thin or sporadic ice cover during the coldest parts of midwinter, so the water circulates and is isothermal during the winter.
  • Winter-stratified monomictic lake
    The aquatic community of a large, shallow lake that has only one period of mixing each year because it is very shallow in relation to its size, and is completely exposed to winds. These lakes typically never become thermally stratified in the summer, and are only stratified in the winter when they freeze over, and become inversely stratified (coldest water at the surface). They are eutrophic to mesotrophic.

Associated Species [-]
  • Common Merganser (Mergus merganser)