Fall Asleep While Learning About The Common Loon

In this episode of the I Can't Sleep Podcast, fall asleep while learning about the common loon. What a fascinating bird! I learned more than I expected about this one. I assumed they were a lot like ducks, but they’re unique enough that I can’t stop thinking about them. For example, their bones are solid, making them heavier than other birds, which allows them to dive deep underwater to get their food.

Let me know if you make it that far in the episode—I’ll be surprised. Happy sleeping!

Transcript

Welcome to the I Can't Sleep Podcast,

Where I read random articles from across the web to bore you to sleep with my soothing voice.

I'm your host,

Benjamin Poster,

And today's episode is from a Wikipedia article titled The Common Loon.

The common loon,

Or Great Northern Diver,

Is a large member of the loon or diver family of birds.

Breeding adults have a plumage that includes a broad black head and neck with a greenish,

Purplish,

Or bluish sheen,

Blackish or blackish-gray upper parts,

And pure white underparts,

Except some black on the undertail coverts and vent.

Non-breeding adults are brownish,

With a dark neck and head marked with dark gray-brown.

Their upper parts are dark brownish-gray with an unclear pattern of squares on the shoulders,

And the upper parts,

Lower face,

Chin,

And throat are whitish.

The sexes look alike,

Though males are significantly heavier than females.

During the breeding season,

Loons live on lakes and other waterways in Canada,

The northern United States,

Including Alaska,

And southern parts of Greenland and Iceland.

Small numbers breed on Svalbard and sporadically elsewhere in Arctic Eurasia.

Common loons winter on both coasts of the U.

S.

,

As far south as Mexico,

And on the Atlantic coast of Europe.

Common loons eat a variety of animal prey,

Including fish,

Crustaceans,

Insect larvae,

Mollusks,

And occasionally aquatic plant life.

They swallow most of their prey underwater,

Where it is caught,

But some larger items are first brought to the surface.

Loons are monogamous,

That is,

A single female and male,

Often together,

Defend a territory and may breed together for a decade or more.

Both members of a pair build a large nest out of dead marsh grasses and other plants formed into a mound along the vegetated shores of lakes.

A single brood is raised each year from a clutch of one or two olive-brown oval eggs with dark brown spots,

Which are incubated for about 28 days by both parents.

Fed by both parents,

The chicks fledge in 70 to 77 days.

The chicks are capable of diving underwater when just a few days old,

And they fly to their wintering areas before ice forms in the fall.

The common loon is assessed as a species of least concern on the IUCN Red List of Endangered Species.

It is one of the species to which the Agreement on the Conservation of African Eurasian Migratory Waterbirds applies.

The United States Forest Service has designated the common loon a species of special status because of threats from habitat loss and toxic metal poisoning in its U.

S.

Range.

The common loon is the provincial bird of Ontario,

And it appears on Canadian currency,

Including the $1 loonie coin and a previous series of $20 bills.

In 1961,

It was designated the state bird of Minnesota and appears on the Minnesota State Quarter.

The common loon is also known as the Great Northern Diver in Eurasia.

Another former name,

Great Northern Loon,

Was a compromise proposed by the International Ornithological Committee.

It is one of five loon species that make up the genus Gavia,

The only genus of the family Gavidae and other gaviformes.

Its closest relative is another large black-headed species,

The yellow-billed loon,

Or white-billed diver.

There are no recognized subspecies of the common loon.

Danish zoologist and mineralogist Morten Thrain-Brunnig first described the common loon in 1764 as Collimbus emer in his Ornithologia borealis.

The now-defunct genus Collimbus contained grebes as well as loons,

And remained in use until the International Commission on Zoological Nomenclature attempted to clarify the nomenclature in 1956 by declaring Collimbus a suppressed name unfit for further use,

And establishing Gavia,

Created by Johann Reinhold Forster in 1788,

As the valid genus name for the loons.

The current genus name Gavia was the Latin term for an unidentified seabird,

And the specific emer is derived from a Norwegian name for the bird,

Similar to the modern Icelandic word kimbrimi.

The word may be related to Swedish emer and emmer,

The grey or blackened ashes of a fire,

Referring to the loon's dark plumage,

Or to Latin emergo,

To immerse,

And immersus,

Submerged.

The European name diver comes from the bird's practice of catching fish by diving.

The North American name loon was first recorded in this sense in New England's Prospect 1634,

By William Wood,

1580-1639.

The loon is an ill-shaped thing,

Like a cormorant.

It may be derived from Old Norse lumer,

As are modern Swedish and Danish loom,

In each case referring to the distinctive call.

A number of fossil loon species are known from the Pliocene,

And specimens from the Pleistocene of California and Florida appear to represent a paleo-subspecies of the common loon.

The adult common loon can range from 66-91 cm in length,

With a 127-147 cm wingspan,

Slightly smaller than the similar yellow-billed loon.

On average it is about 81 cm long,

And has a wingspan of 136 cm.

Its weight can vary anywhere from 2.

2 to 7.

6 kg.

Sizes vary regionally,

Especially by body mass,

With the smallest-bodied loons on average from lower central Canada and the Great Lakes,

While westerly birds are similar or mildly larger,

And loons breeding further east can appear to be significantly larger.

Furthermore,

Males average up to nearly 27% more massive than females in some populations.

Breeding loons in Maine averaged 4.

65 kg in females and 5.

97 in males,

Essentially the same weight as a yellow-billed loon.

Although the yellow-billed is still larger than in linear dimensions,

Especially bill length,

Than the Maine loons.

In Ontario,

20 females averaged 4.

5 kg and 20 males averaged 5.

46 kg.

In contrast,

In the Gulf of Alaska,

Adults of both sexes reportedly averaged 4.

13 kg.

Adult breeding plumage consists of a broad black head and neck with greenish,

Purplish,

Or bluish sheen.

It has a black bill,

Sometimes with a pale tip,

And red eyes.

The neck is encircled with a characteristic black ring,

And has two white necklaces of 8 to 10 short streaks on the upper foreneck,

And a noticeable collar of white parallel lines forming a large oval on the neck side.

The central lower foreneck is pure white,

And the lower neck side has longitudinal white lines becoming rows of small spots and black lines becoming very narrow.

The upper parts are blackish or blackish-gray,

And each feather has small white spots on it.

The upper wing is blackish and with small white spots on the non-primary coverts,

Whereas the underwing is paler with white coverts,

Except the long black shaft streaks on the axillaries.

The underparts are pure white,

But have some black on the undertail,

Coverts,

And vent.

It has a checkered black and white mantle,

And a blackish tail.

The legs are pale gray on the inner half and blackish on the outer half,

And the webs between the toes are flesh-colored.

Adult non-breeding plumage is brownish,

With a dark neck and head marked with dark gray-brown.

The eyes are surrounded with white,

And the eyelids are pale.

The bill is mostly pale gray,

With a dark Coleman and tip,

But in early spring the tip may turn whitish.

The underparts,

Lower face,

Chin,

And throat are also whitish.

The foreneck is whitish,

Usually forming wedge-shaped notch in dark neck sides,

And may sometimes reveal a shadowy trace of the neck ring or a pale collar.

It has dark brownish-gray upper parts,

With an unclear pattern of squares on the shoulders,

And some wing coverts spotted with white,

Which are usually concealed while swimming.

The male and the female have similar appearances,

Although they exhibit sexual dimorphism in their physical dimensions,

With the male larger and significantly heavier than the female.

The heavy dagger-like bill is evenly tapered and grayish,

Sometimes having a black tip.

The bill color and angle distinguish this species from the yellow-billed loon.

The neck is short and thick.

The common loon swims very low in the water,

With sometimes only its head held above and horizontal to the surface.

It must run across the water surface to get in flight.

During flight,

Its head is slightly lower than its body,

With its feet trailing behind.

It has a skeletal structure made up of a number of solid bones.

This is usual for the gaviforms in penguins,

But unlike most flying birds which have bones with extensive pneumatization,

Hollow and filled with air to make the skeleton lighter,

Which adds weight,

But helps in diving.

A juvenile often has a dark brownish-gray nape that may look darker than the pale-edged black feathers.

It has a dark gray to black head,

Neck,

And upper parts,

With white throat,

Cheeks,

And underparts.

During the first winter,

The bill shape of the young may not be as fully developed as that of the adult,

And during the second winter it much resembles the breeding adult,

But with wing coverts lacking white spots.

The common loon is distinguished from the black-throated loon and the red-throated loon mainly by its larger size.

It usually has a steeper forehead and a bulging forecrown,

Somewhat similar to the black-throated loon.

Its bill is heavier,

And the back is paler than its hind neck.

It is more difficult to separate from the yellow-billed loon,

But its breeding plumage has more wide markings on the neck and the squares on its shoulders are usually smaller.

The non-breeding plumage has darker neck sides,

Contrasting more sharply with pale areas and bill color.

The scaly juvenile plumage is retained until January or February of the year following hatching,

When a lengthy mold of head and body feathers gives them a more adult-like appearance.

Adults shed all their flight feathers simultaneously around this time,

Leaving them temporarily flightless prior to gaining breeding plumage,

But second-year birds delay this substantial mold until the summer.

The adult winter plumage is attained between October and January by partial mold mainly of head,

Body,

And tail feathers.

With improved gene sequencing technology,

A draft genome of the common loon has assembled and identified at least 14,

169 genes.

80.

7% of chicken genes are found in the common loon genome.

The physiological costs of deep-water diving and long-distance aerial migration of loons have greatly affected loon evolution.

Many identified genes are candidate genes for positive selection,

Since the common loon chicken split 90 million years ago.

It is theorized that these candidate genes are related to hemoglobin affinity for oxygen,

Solute exchange,

Immunoglobulin function related to immune defense,

Nervous system development,

And a number of molecular pathways related to DNA metabolic function,

And G-receptor pathways potentially involved in low-light visual acuity.

For example,

SLC48A and SLC20A1 are candidate genes in the Gavia lineage for maintaining homeostasis due to maybe having a role in maintaining ion and pH balance.

Common loons are mainly in the Arctic and breed from 48 degrees north to the Arctic Circle,

Locally south to 40 degrees north,

And north to 78 degrees north.

During their breeding season in spring and summer,

Most common loons live on lakes and other waterways in the northern United States and Canada,

As well as in southern parts of Greenland,

In Iceland,

In Svalbard,

In Jan Mayen,

And in Bear Island in Norway,

And in Alaska to the west,

And very rarely in Scotland to the east.

Their summer habitat ranges from wooded lakes to tundra ponds.

The lakes must be large enough for flight take-off and provide a large population of small fish.

Deep lakes with warm surface waters,

Relatively low biological productivity,

And low turbidity where their fish prey are easy to see are habitats where breeding loons are more successful in raising young.

For protection from predators,

Common loons favor lakes with islands and coves.

They are rare visitors to the Arctic coast.

They are known to exhibit high breeding site fidelity.

Some common loons remain in Iceland year-round,

Although most migrate.

In North America,

They winter mainly along north Atlantic and northeast Pacific coasts,

Many stopping off on the Great Lakes during their migration.

They migrate in the day,

Starting about two hours after sunrise,

And flying at altitudes of 1,

500 to 2,

700 meters above sea level,

Above the convective and turbulent layer of air.

In winter,

They can be seen on North America coasts as far as Baja California,

Sonora,

Northern Sinaloa,

Southern Texas,

And rarely northern Tamaulipas.

In the east,

Several thousand winter along western European coasts,

Probably originating from Iceland,

Greenland,

And Canada.

Their range extends into northwestern Europe from Finland to Portugal,

And southern and northwestern Spain,

As well as the western Mediterranean off Catalonia,

And off Morocco and Africa,

Although only a few hundred travel as far south as Iberia.

Although wintering site fidelity is not well known,

Annually adults are observed to return to the same wintering locations in the Pacific Ocean,

The Gulf of Mexico,

The Atlantic Ocean,

And the reservoir Lake Boteros.

They usually winter along coasts and on inland lakes,

Bays,

Inlets,

And streams,

With birds migrating to the nearest body of water that will not freeze over in the winter.

Western Canadian loons go to the Pacific,

Great Lakes loons to the Gulf of Mexico region,

Eastern Canadian loons to the Atlantic,

And some loons to large inland lakes and reservoirs.

They appear in most of the inland waters of the United States.

The South Carolina coast,

The Gulf coast adjacent to the Florida Panhandle,

And the Atlantic seaboard from Massachusetts to Maine have some of the highest concentrations of common loons.

Occasional vagrants are recorded inland in Mexico,

In San Luis Potosi and Coahuila,

As well as Chiapas and Oaxaca in the south.

They are accidental in northern Japan and the Commander Islands in northwestern Pacific and Cuba in the West Indies.

The common loon is an expert fisher,

Catching its prey underwater by diving as deep as 60 meters.

With its large webbed feet,

The common loon is an efficient underwater pursuit predator and a droid diver.

It needs a long run-up distance to gain momentum for flight take-off and is ungainly on land,

Sliding on its belly and pushing itself forward with its legs.

Its clumsiness on land is due to the legs being positioned at the rear of its body.

The pelvic muscles are well-developed,

Ideal for swimming but not well-suited for walking.

When it lands on water,

It skims along on its belly to slow down,

Rather than breaking with its feet as they are set too far back.

The common loon swims and dives well and flies competently for hundreds of kilometers of migration.

It flies with its neck outstretched,

Usually calling a particular tremolo that can be used to identify a flying loon.

Its flying speed is as much as 120 kilometers per hour during migration.

Particularly during the breeding season,

Common loons frequently engage in territorial disputes against other water birds,

Including ducks and geese,

And will attack or drive off competitors and intruders to their territory.

Fish account for about 80% of the diet of the common loon.

It forages on fish of up to 26 centimeters in length,

Including minnows,

Suckers,

Gizzard chad,

Rock bass,

Alewife,

Northern pike,

Whitefish,

Sauger,

Brown bullhead,

Pumpkin seed,

Burbot,

Walleye,

Bluegill,

White crappie,

Black crappie,

Rainbow smelt,

And killifish.

The young typically eat small minnows,

And sometimes insects and fragments of green vegetation.

The freshwater diet primarily consists of pike,

Perch,

Sunfish,

Trout,

And bass.

The saltwater diet primarily consists of rockfish,

Flounder,

Sea trout,

Herring,

Atlantic croaker,

Haddock,

And gulf silverside.

When there is either a lack of fish or they are difficult to catch,

It preys on crustaceans,

Crayfish,

Snails,

Leeches,

Insect larvae,

Mollusks,

Frogs,

Annelids,

And occasionally aquatic plant matter such as pondweed,

Roots,

Moss,

Willow shoots,

Seeds,

And algae.

The common loon uses its powerful hind legs to propel its body underwater at high speed to catch its prey,

Which it then swallows headfirst.

If the fish attempts to evade the common loon,

The bird chases it down with excellent underwater maneuverability due to its strong legs.

Most prey are swallowed underwater,

Where they are caught,

But some larger prey are first brought to the surface.

It is a visual predator,

So it is essential to hunting success that the water is clear.

It normally dives 4 to 10 meters,

But has been recorded to dive up to 70 meters.

The average diving time is 42 seconds,

But the maximum duration spent underwater is about 1 minute.

The common loon's mating system is serially monogamous.

Breeding pairs jointly defend a territory consisting of an entire small lake or a protected bay within a large lake.

A given male and female remain together throughout a breeding attempt,

Rear their own biological offspring,

Reunite each spring,

And may breed together for many consecutive years.

However,

In the event of death or territorial eviction of one pair member by an intruding loon of the same sex,

The other pair member quickly establishes a pair bond with the evicting bird.

Hence,

Most adult loons have two or more different mates during their lives.

Evicting individuals tend to be young males and females,

5 to 9 years old,

While evicted adults are often those 15 years and older.

Pairs do not remain together during winter.

In addition,

Males usually precede females by a few days to a few weeks during spring migration,

Settling on their lake once a portion of it becomes ice-free.

Nesting typically begins in early May.

Significantly more nesting sites are found on islands than on mainland shoreline.

Breeding pairs patrol their territories routinely,

Even at night,

Defending the territory both physically and vocally.

Pairs that nested together the preceding year typically reused the nest site from the previous year if they hatched chicks successfully there.

In contrast,

Pairs that lost their eggs to a predator usually shift the nest to a new location.

This logical behavior pattern appears to depend upon the male,

Because breeding pairs consisting of last year's male and a female not present during the preceding year continue to exhibit the behavior.

Pairs composed of last year's female and a new male tend to select a new nest site,

Regardless of the success or failure of the previous year's attempt.

Despite the lead role of males in nest site selection,

Both sexes contribute substantially to nest construction.

The nest is about 56 centimeters wide and is constructed out of dead marsh grasses and other indigenous plants,

And formed into a mound along the vegetated coasts of lakes greater than 3.

7 hectares.

After a week of construction in late spring,

One parent climbs on top to mold the interior of the nest to the shape of its body.

Based on a number of studies,

Nesting success averages about 40%,

And most newly hatched young survive due to parental care.

Eggs from first clutches are typically laid in May or early June,

A timing depending largely upon the date that lakes become ice-free and inhabitable.

A clutch consists of two,

Occasionally one,

Olive-brown oval eggs with dark brown spots.

Incubation is carried out jointly by male and female,

And lasts about 28 days.

Loons often place nests along steep lake shorelines where adults can quickly dive underwater when approached by predators.

The eggs are about 88 millimeters long and 55 millimeters wide,

And the two eggs are laid with an interval of one to three days between them,

And hatch asynchronously.

Newly hatched chicks are dark chocolate brown in color and have a white belly.

Within hours of hatching,

The young begin to leave the nest with the parents,

Swimming close by and sometimes riding on one parent's back.

Parents and chicks initially stay in shallow,

Isolated bays where the parents are able to defend the chicks better from intruding loons and eagles,

Which are their main predators.

Male parents defend broods consisting of two chicks more vigorously than singleton chicks,

Chiefly with the territorial yodel call.

The chicks are capable of making shallow dives from their first day,

But make deeper dives as they grow.

Fledging takes 70 to 77 days.

Usually only one brood is raised.

Both parents feed the chicks live prey from hatching to fledging.

As they grow,

Chicks are able to catch an increasingly large proportion of their diet by themselves.

They can feed and fend for themselves after about two months,

Although many juveniles continue to beg from adults well beyond this age.

The parent birds capture small fish and hold them crosswise in their bill,

Call and approach the chicks with their head lowered so the chicks can grasp them.

Juveniles leave the breeding ground before ice formation in the fall,

Weeks after their parents.

A pair of loons raising two chicks have been estimated to feed on 423 kilograms of fish during the five and a half months that they spend in their breeding territory.

Loons exhibit a strong tendency to settle as breeders on a lake that resembles their natal one,

A phenomenon termed natal habitat imprinting.

This preference is based on two lake attributes,

Size and pH.

The behavior is puzzling because it is as strong in loons hatched on small acidic lakes as those from large lakes of neutral pH.

Hence,

The former group is exhibiting active preference for lakes that have been shown to result in higher chick mortality and lower breeding success.

The common loon produces a variety of vocalizations,

The most common of which are the tremolo,

The yodel,

The wail and the hoot.

Each of these calls communicates a distinct message.

The frequency at which it vocalizes has been shown to vary based on time of day,

Weather and season.

It is most vocally active between mid-May and mid-June.

The wail,

Yodel and tremolo calls are sounded more frequently at night than during the day.

Calls have also been shown to occur more frequently in cold temperatures and when there is little to no rain.

The tremolo call,

Sometimes called the laughing call,

Is characterized by its short,

Wavering quality.

It often uses this call to signal distress or alarm caused by territorial disputes or perceived threats.

It emits a tremulous series of up to 10 rather high notes.

It also uses the tremolo to communicate its presence to other loons when they arrive at a lake,

Often when they are flying overhead.

It is the only vocalization used in flight.

The tremolo call has varying three levels of intensities that correlate with a loon's level of distress,

And the types are differentiated by increasingly higher pitch frequencies added to the call.

The yodel is a long and complex call made only by the male.

It is used in the establishment of territorial boundaries and in territorial confrontations and the length of the call corresponds with a loon's level of aggression.

The dominant frequencies in the yodel indicate the body mass and thereby the health of males.

A male that occupies a new territory appears to alter its yodel to be clearly distinguishable from the call of the previous territory owner.

A loon's wail is a long call consisting of up to three notes and is often compared to a wolf's howl.

It uses this call to communicate its location to other loons.

The call is given back and forth between breeding pairs or an adult and its chick,

Either to maintain contact or in an attempt to move closer together after being separated.

The hoot is a short,

Soft call and is another form of contact call.

It is a more intimate call than the wail and is used exclusively between small family groups or flocks.

A common loon hoots to let other family or flock members know where it is.

This call is often heard when the adult loon is summoning its chicks to feed.

Reviews

Couldn’t help but think of the film On Golden Pond. I went right to sleep. Thanks!