Common Loon Common Loon
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Loon Migration Update: April 5, 2001

Today's Report Includes:

Look Out for Loons!
Loons appear like clockwork in late March and early April, as today's 89 sightings show. The loons are flooding inland, but they haven't reached some northern states or Canada yet. You probably know why! As you make your migration map today, consider why the loons are appearing WHERE they are, WHEN they are. (You'll find some help in today's topics.)

Last time we promised this map would show LOT of loons moving--and some already reaching the finish line! Sure enough, loons have been filling the skies and reported as "flyovers seen only as specks." They've been sighted from the Intracoastal Canal in Creole, LA to quarry ponds in Rockford, IL; from reservoirs in Burton Station, OH to the lakes of Wisconsin and Michigan. "The river was alive with birds, including two common loons," came word from West Fairview, PA. In Royal Oak, MD, several loons were heard yodeling. From Kemper Lakes, Long Grove, IL, came this description:

"One gave us a nice display of active preening, flapping, and short (but fast!) runs across the water in addition to its usual long disappearances underwater. The second loon would occasionally surface closer to the first one, only showing its head above the water, like it was sneaking up on it."

Welcome home, loons! Males and females arrive separately on the breeding grounds. What's next for the new arrivals?

Scouting a Territory
One of an animal's most basic needs is a suitable area for breeding. Animals (like loons) that breed on territories face a double whammy. Not only must they find suitable habitat, but they must also compete with other loons to keep it. Good breeding territories--those on which chicks are produced every year--are scarce in some places, such as northern Wisconsin. Most loons know that the fastest way to get a good territory is to kick someone else out of theirs. Adult loons that lack territories make regular visits to territories of breeding pairs. We wonder how you would answer:

Challenge Question #10:
"Why does it make sense for adult loons without territories to make regular visits to territories of breeding pairs?"

(To respond to this question, please follow the instructions below.)

Talking About Takeovers

Walter Piper looks for loons

This is the time of year when loons scope out territories. Journey North is proud to introduce you to an expert in the subject. Dr. Walter Piper spends each summer studying common loons. Together with his colleagues, he's made some fascinating discoveries. Dr. Piper likes researching why loons barge into other loons' territories, events called territorial intrusions. A loon that visits or tries to take over another loon's territory is called an intruder, so now you know the vocabulary. Dr. Piper and co-investigators Keren Tischler and Margaret Klich studied territory acquisitions of loons in northern Wisconsin. They found that:
  • 41.5% of territory acquisitions came through passive occupancy of territory left vacant after another loon died or deserted the territory;

  • 17% were due to the founding of new territories; and,

  • 41.5% came through takeovers (an intruder drove off the loon already there, or else arrived on the territory before the "previous owner" made it back to the territory). That's the importance of takeovers!

Photo Courtesy Woody Hagge

Mated pairs defend territories, and you might be surprised to learn that BOTH males and females can be kicked off their territories by intruders. "It usually results from a short battle, but the fighting can last several days and be fatal," says Dr. Piper. What happens then? "In all such cases, the mate of the displaced bird quickly pairs with the usurper (the intruder that won), leaving its mate to fend for itself. Displaced birds (those kicked off) often regain a territory, either the one they lost (usually following the usurper's death) or another territory. Quite often they find new territories with new mates." Intruders gain breeding status by displacing one member of a breeding pair. You might say that breeding status is what loons live for.

Next time Dr. Piper helps us understand how scientists figure out just what territorial intruders are looking for--a research challenge he faced. How would YOU figure it out? Give it some thought:

Challenge Question #11:
"How do scientists narrow down the possibilities of what intruders are looking for?"

(To respond to this question, please follow the instructions below.)

Teacher Tip: Yo! Whose Yodel is That?
Like your own voice, the yodel call of a male loon is one of a kind. Research has verified that each male loon's yodel is a distinctive "voice print" that stays the same while the loon is on breeding territory. A male's territorial yodel discourages visits by intruders. Dr. Walter Piper says, "Once we can identify a bird as an individual, we can learn a tremendous amount about its reproductive behavior, fidelity to a mate and territory, and tendency to wander around its breeding lake." However, preliminary data indicate that a male's yodel might change substantially if that loon is chased off its territory by another male loon and forced to move elsewhere.

Dr. Piper sent us three loon yodels. He can tell these loons apart just by their yodels. Can you? Try your ear at distinguishing the yodels of three different males from three different lakes. Then SEE those yodels with pictures of the sounds, called sonograms. How helpful will vocal tagging be if loons really do change yodels when they change territories? Go to:

Loons and Lakes With Ice
Ted Gostomski, Staff Biologist and Loon Watch Coordinator at Sigurd Olson Environmental Institute, had this comment about a sighting in our last report: "That sighting you reported on Lake Monona is interesting because I was down there about that time, and the amount of open water wasn't great. I mean, it was enough for a loon to get on and off of for sure, but a lot of the lake was still frozen. In any case, I'm sure reports will start rolling in once that ice goes out!" Ted was right, as this week's migration map shows.

The Lake Monona loon was reported on March 19. This isn't an exceptionally early date, but there WAS something exceptional about this sighting. The lake was mostly ice-covered when the first loon was seen, with only about 10% open water! What's the connection between loons returning and ice-out on lakes?

Loons almost always wait for a lake to be mostly or even entirely open before they land. They don't have any trouble landing in a small patch of open water, but they CAN have trouble taking off again! Loons are large, heavy birds that have small wings. (Big, light-weight wings make diving harder.) The only way loons can get their heavy bodies into the air is to run straight into the wind on the water's surface, flapping their wings as fast as they can. If the open patch of water is too short, they're stuck, and if very cold weather returns and the rest of the lake freezes, the loon is REALLY stuck. Of course, in springtime the water is likely to become more open day after day, so this loon wasn't in serious trouble as it waited for more open water in other places. But landing in Lake Monona when there was still so much ice around is a good example for one of the hazards of migrating just a little too early! (For more on those hazards, see Discussion of Challenge Question #7, below.)

Teacher Tip: Flying Loons
How is a landing loon like a hundred-pound box with a tiny parachute? Why do loons have to be so careful when coming in for a landing? Learn about the special requirements loons have for taking off and staying in the air with our loon flight lesson:

On the Mark, Get Set, Go! Discussion of Challenge Question #7
"What are some of the advantages (A) and disadvantages (D) of being among the FIRST loons to migrate? What are some of the advantages and disadvantages of being among the LAST loons to migrate?" Congratulations to Jan Herbertís class from Park Rapids, MN, who had most of these answers:

Being First:
  • Lakes might be frozen and they couldn't land or find food. (D)

  • Risking the worst weather of spring, including blizzards, ice storms, and tornados. (D)

  • Losing eggs and chicks to cold and other weather-related causes. (D)

  • Eggs and chicks can be lost from other things, too, especially predators. Early loons have more opportunity for re-nesting if necessary.

  • Best choice of nesting sites. (A)

Being Last:

  • Nesting sites and mates could all be taken when late birds arrive. (D)
  • Spending more time on the ocean means getting into top condition before migrating. (A)
  • When they migrate, the ice is out everywhere along the way so they can find food all along the way. (A)
  • The weather when they arrive is more predictable and warmer. (A)

One middle school class suggested that later migrants could maybe take the nests of the first. These students showed excellent reasoning. Some cavity nesters do that, but loons always build their own nests, regardless of when they return.

Feather Wetsuits: Discussion of Challenge Question #8
"How do a loon's beak, eyes, legs, and feet stay warm when exposed to cold water?"

We were very impressed with how well several of you researched and reasoned through this question, including Mrs. Nunnally's class at Peter Woodbury School in Bedford, NH (good thinking, second graders!). Hereís how Christian, Richard, Dana, and Lori from Iselin Middle School Grade 7 explain it:

"A loon's beak, legs, and feet stay warm when exposed to cold water because the loon's beak is made of the same kind of tissue as our finger nails, without a blood supply that could get cooled by the air and then travel through the rest of the body. The legs and feet have a much smaller blood flow than our legs and feet. In the loon, blood flowing from the cold feet back up into the warm body gets heated as it travels in vessels right next to the hot blood."

Early or Late: Discussion of Challenge Question #9
"What advantages can you list for loons to molt on the ocean instead of on their summer lakes?"
  • They need their energy in summer for nesting and raising chicks.
  • They have extra energy for molting in winter from eating nutritious ocean food.
  • Salt water and relentless sun is hard on feathers. (There are no trees in the ocean to provide shade!)
  • Loons hardly need to fly at all while wintering on the ocean, so old flight feathers aren't critical while they are there. But by the end of the season the flight feathers could be too worn to be effective for migrating so thatís when they molt. Thatís why Ms. Herbert's class from Park Rapids, MN, told us that "if they didn't molt before they went north they wouldn't make it."
  • Fresh water is easier on feathers than salt water, so the newly-molted feathers of spring can last through two migrations, carrying a loon to the breeding lake and then back to the ocean.

How to Respond to Today's Challenge Questions:

IMPORTANT: Answer only ONE question in each e-mail message.

1. Address an e-mail message to: jn-challenge-loon@learner.org
2. In the Subject Line of your message write: Challenge Question #10 (or #11).
3. In the body of your message, give your answer to ONE question.

The Next Loon Migration Update Will be Posted on April 19, 2001

Copyright 2001 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form

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