Common loon

The black-and-white diving bird whose call carries across Glacier's lakes; one in five of Montana's nesting loons is inside this park.

  • Two loons on a Glacier lake in the rain. Note how low they ride, almost level with the water.NPS / Jacob W. Frank
  • Up on the water with wings out. Getting airborne means running across the surface like this until there is enough speed.GlacierNPS
  • Airborne, with the feet trailing behind. Those feet are propellers, not landing gear.NPS / Jacob W. Frank

Common loon at a glance

Gavia immer LOON; Gavia immer is GAY-vee-uh IM-mer

Type
Bird · loon
Diet
Carnivore
Size
About as heavy as a full gallon jug of milk, 8 to 12 pounds (NPS), and built the wrong way round for walking: its legs sit so far back that it can barely move on land.
Lifespan
Long-lived for a bird, about 25 to 30 years (NPS).
Conservation
Not federally listed. Montana lists the common loon as a Species of Concern; the Montana Natural Heritage Program ranks it G5 globally and S3B for breeding birds in the state.

Eats fish, aquatic insects, crayfish

It hunts underwater by sight. NPS describes large webbed feet and legs set far back on the body that let it drive itself along under the surface, and an ability to blow air out of its lungs and squeeze it out of its feathers so it can dive instantly.

Should you worry?

No danger to you. You are the danger to it. NPS says the biggest threat to loons is human disturbance, and getting too close can make a parent abandon a nest. Watch from shore or keep the boat well off. If anybody in your group fishes, take every scrap of line home: discarded line tangles loons, and swallowed lead sinkers kill them.

You will hear it before you see it. A long rising wail comes off the lake, crosses the whole of it, and then nothing. NPS files that call under long-distance communication, which is a plain way of saying it is one loon trying to reach another loon somewhere out there in the dark. Three more calls are worth learning while you listen: a yodel, which only males make and only about territory; a tremolo, the shaky one an upset bird makes; and a hoot, soft and short, passed between a parent and its chick.

Then find the bird. It sits low, almost level with the surface, black head, white chest, a back checkered black and white like a chessboard, and a bill like a spike. It is riding low for a reason.

Here is the trade. Every bird book tells you birds have hollow bones. A loon’s are solid. That extra weight is what lets it sink instead of bob, and it can go further: NPS describes it blowing the air out of its lungs and squeezing the air out of its feathers so it can dive instantly. Watch one long enough and you will see it happen. No jump, no splash, just a bird and then no bird. Underwater it hunts fish by sight, driving itself with big webbed feet set far back on its body, where a boat would put the propeller.

The bill for all that comes due in the air. A loon is too heavy to leap into flight. It has to run across the top of the water, flapping, until it has enough speed, which means it needs a long open lake to leave from. Legs set that far back are also nearly useless on land, so it can barely walk. It bought a better swimmer by giving up almost everything else.

Glacier matters to this bird more than its size suggests. One-fifth of Montana’s nesting loons are inside this park. Volunteers and park staff have been trained since 2005 to check 45 priority loon lakes, and the count comes out around 44 adults and 8 chicks a year. That is a small number of birds spread across a lot of water, which is the whole reason for the next paragraph.

You are the danger here, not the loon. NPS says human disturbance is the biggest threat, and a parent pushed off a nest may not come back to it. So watch from shore, or keep the boat far off and keep it slow. If anyone in your group fishes, count the line back into the pack, all of it: loose line tangles loons and swallowed lead sinkers kill them. Then sit down on the bank, be quiet, and wait for the wail.

Did you know?

  • Its bones are solid, not hollow like most birds'. That is what lets it sink and dive, and it is also why it needs a runway. NPS: "In order to achieve flight, they run on top of the water, flapping their wings to gain enough momentum for liftoff."
  • It has four calls with four jobs. NPS lists a wail for talking long distance, a yodel that only males make to claim territory, a tremolo from an upset bird, and a hoot passed between adults or between a parent and its young.
  • Ordinary people count them. Since 2005, trained volunteers and park staff have checked 45 priority loon lakes in Glacier, and the data show an average of 44 adult loons and 8 chicks per year.

Common questions

Why is it so hard for a loon to take off?

Because it traded flight for diving. Most birds have hollow bones. A loon's are solid, which makes it heavy enough to sink on purpose, and too heavy to jump into the air. It has to run across the surface of the lake flapping until it gets enough speed.

How does it sink without splashing?

It blows the air out of its lungs and squeezes it out of its feathers. Less air means less float. One second it is on the surface, the next it is gone, and no dive splash in between.

What is the noise it makes at night?

Probably a wail, the call loons use to reach each other over distance. Three others are worth learning: the yodel a male uses on his territory, the tremolo of an upset bird, and the soft hoot between a parent and a chick.

How many loons are in Glacier?

One-fifth of Montana's nesting loons are in this park, and the long-running count on 45 monitored lakes averages 44 adults and 8 chicks a year. That is not many birds spread across a park this size, which is why staying back from them matters.

Where it lives

Where we got this