Loons are excellent swimmers, using their feet to propel themselves above and under water. However, since their feet are located far back on the body, loons have difficulty walking on land, though they can effectively run short distances to reach water when frightened. Thus, loons avoid coming to land, except for mating and nesting. Loons fly strongly, though they have high
wing loading (mass to wing-area ratio), which complicates takeoff. Indeed, most species must run upwind across the water's surface with wings flapping to generate sufficient lift to take flight. Only the
red-throated loon (
G. stellata) can take off from land. Once airborne, loons are capable of long flights during migration. Scientists from the U.S. Geological Survey, who have implanted satellite transmitters in some individuals, have recorded daily flights of up to 1078 km in a 24-hour period, which probably resulted from single movements. North European loons migrate primarily via the South Baltic and directly over land to the Black Sea or Mediterranean. Loons can live as long as 30 years and can hold their breath for as long as 90 seconds while under water. Loons are migratory birds, and in the winter, they move from their northern freshwater lake nesting habitats to southern marine coastlines. They are well-adapted to this change in salinity, however, because they have special salt glands located directly above their eyes. These glands filter out salts in their blood and flush this salty solution out through their nasal passages, which allows them to immediately consume fish from oceans and drink saltwater after their long migration. Common loons sometimes form social gatherings of several adults in late summer. Studies in North America suggest that these events are attended largely by nonbreeding individuals and relate to territory assessment and social familiarity rather than foraging or migration.
Diet and feeding Loons find their prey by sight. They eat mainly
fish, supplemented with
amphibians,
crustaceans, and similar midsized aquatic
fauna. Specifically, they have been noted to feed on
crayfish,
frogs,
snails,
salamanders, and
leeches. They prefer clear lakes because they can more easily see their prey through the water. Loons use their pointy bills to stab or grasp prey. They eat
vertebrate prey headfirst to facilitate swallowing, and swallow all their prey whole. To help digestion, loons swallow small pebbles from the bottoms of lakes. Similar to
grit eaten by
chickens, these
gastroliths may assist the loon's
gizzard in crushing the hard parts of the loon's food, such as the
exoskeletons of crustaceans and the bones of frogs and salamanders. The gastroliths may also be involved in stomach cleaning as an aid to regurgitation of indigestible food parts. Loons may inadvertently ingest small
lead pellets, released by anglers and hunters, that will contribute to
lead poisoning and the loon's eventual death. Jurisdictions that have banned the use of lead shot and sinkers include
Maine,
New Hampshire,
Vermont,
Michigan, some areas of
Massachusetts,
Yellowstone National Park,
Canada,
Great Britain, and
Denmark.
Reproduction Loons nest during the summer on freshwater lakes and/or large ponds. Smaller bodies of water (up to 0.5 km2) usually only have one pair. Larger lakes may have more than one pair, with each pair occupying a bay or section of the lake. The red-throated loon, however, may nest colonially, several pairs close together, in small Arctic
tarns and feed at sea or in larger lakes, ferrying the food in for the young. Most
clutches consist of two eggs, which are laid in May or June, depending upon latitude. Loon chicks are
precocial, able to swim and dive right away, but will often ride on their parents' back during their first two weeks to rest, conserve heat, and avoid predators. Chicks are fed mainly by their parents for about six weeks, but gradually begin to feed themselves over time. By 11 or 12 weeks, chicks gather almost all of their own food and have begun to fly.
Biologists, especially from
Chapman University, have extensively studied the mating behaviour of the
common loon (
G. immer). Contrary to popular belief, pairs seldom
mate for life. Indeed, a typical adult loon is likely to have several mates during its lifetime because of territorial takeover. Each breeding pair must frequently defend its territory against "floaters" (territory-less adults) trying to evict at least one owner and seize the breeding site. Territories that have produced chicks in the past year are especially prone to takeovers, because nonbreeding loons use chicks as cues to indicate high-quality territories. One-third of all territorial evictions among males result in the death of the owner; in contrast, female loons usually survive. Birds that are displaced from a territory but survive usually try to re-mate and (re)claim a breeding territory later in life. In 2020, a loon hatched for the first time in over a century in Southeastern Massachusetts at Fall River. The chicks had been relocated in 2015 from Maine and New York to the Lakeville, Massachusetts with the hopes of re-establishing breeding and nesting patterns. ==Etymology and taxonomy==