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Loon Migration Update:April 19, 2001
Today's Report Includes:
- A Big Jump! This Week's Migration Map and Data
- Ice Out? Loons On!
- What's the Rush? Challenge Question #12
- Loon Myths or Facts? Challenging Old Beliefs
- Try This!
- Earth Day Message
- Going Fishing? Get the Lead Out: Challenge Question #13
- Mercury Alert! Challenge Question #14
- Scouting a Territory: Discussion of Challenge Question #10
- Talking About Takeovers: Discussion of Challenge Question #11
- Ask the Expert--Now Open
- Note To Teachers: We'd Appreciate Your Thoughts!
A Big Jump! This Week's Migration Map and Data
Bright in their beautiful breeding plumage and filling the north with their haunting calls, loons are dropping down into clear northern lakes as fast as the ice goes out. See the jump by comparing these three maps!
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March 22, 2001 |
April 5, 2001 |
April 19, 2001 |
What do you think explains the big jump loons made on this week's map? There's
still plenty of ice covering northern lakes, but we should see a big northerly push
of loons into Canada and the northern parts of the Great Lakes states as the ice
retreats in the next week. Stay tuned!
Ice Out? Loons On!
Observers in many places commented about how the loons were appearing in lakes as soon as the ice was out, and some of them were even landing in lakes that were mostly ice-covered. Loons have been collecting in large numbers in some lakes, probably because so many lakes have remained ice-covered so late. "This was overall not a severe winter, temperature-wise, but spring was very late. Loons were ready, hormonally and plumage-wise, for migrating before many of their lakes were open," says bird expert Laura Erickson. "I'm sure this contributed to their impatience for 'their' lakes to open up!" Here's what's happening:
Donna Millard in Sarona, WI, heard and saw her first loons on April 15. She writes, "Ice is not completely off the lake yet, but there is a good portion of it gone. A good sunny day with warm temps and a good wind should take care of it. Yippee! They're back!"
Mark Alt in Plymouth, MN says "There are a bunch of birds out there looking for open water right now!" We love his description of how they fly: "They're like a flying cross, every branch of the cross tapered to a fine point, the head dropped low like a Concorde SST."
Jeff Holbrook of Canton, NY saw some FAST ice-out for "his" loons: "The breeding pair of Common Loons has returned to Lower Lake. Last year they appeared on April 13. This year they were early--April 10. At that time they could not land on Lower Lake as there was not enough open water for them. Today at lunch when I first spotted them on the lake, there was still only a 60 x 100 yd opening at best. I wondered about that. When I returned after work to check things out I discovered that the amount open water had doubled!" For more on the loon-and-ice connection, see:
What's the Rush?
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Photo Courtesy: Woody Hagge |
This observer sees very different picture during fall and spring migration. In general, loons travel very quickly to their breeding lakes. They "stage" less in spring than in fall, although sometimes a large number of loons can be stopped at an open lake while waiting for ice out on other lakes. That leads us to ask:
Challenge Question #12:
"What are some reasons that migrating loons might be in more of a hurry to reach their destination in spring and less of a hurry to get there in fall?"
(To respond to
this question, please follow the instructions below.)
Loon Myths or Facts? Challenging Old Beliefs
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Walter Piper looks for loons |
- Do loons mate for life? No. Dr. Piper explains: "A typical loon probably has 4-5 different mates during its lifetime. The birds are not paired throughout the year and arrive separately on the breeding ground. The pair bond of loons does not outlast each pair member's ability to defend its breeding position from intruders of its own sex. Both males and females can be driven off their territories by intruders.
- Do loons return to the same territory each year? Dr. Piper says that loons will go back to their territory, but that doesn't mean they'll stay! There's a lot of competition to keep and defend a good territory. Loons aren't always successful, and often lose their breeding places to territorial intruders. The loon that's kicked out departs alone, leaving his or her conqueror and the old mate as the new breeding pair of the territory. Any eggs or chicks produced by the original two birds are lost, although the remaining member of the original pair often attempts to nest again with its new mate. Breeding pairs with good territories put up with dozens to hundreds of intrusions each year. Most intruders arrive and leave fairly quickly, but sooner or later comes an intruder that does NOT leave quickly. This leads to an escalated battle that might cost the resident its territory AND its mate.
You'll learn more as you read Dr. Piper's answers to last week's Challenge Questions#10 and #11, below.
Try This!
Could a loon have a lifetime mate? Write a paragraph explaining the connection between
a loon's mating partner and its territory. Use evidence in today's report to support
your topic sentence.
Earth Day Message
April 22 is Earth Day, but making EVERY day Earth Day would certainly help loons! Common loons are still plentiful in most of Alaska and Canada, but their numbers and range have decreased in the lower 48 United States. The estimated 20,000 loons in the Upper Great Lakes States of Minnesota, Wisconsin, and Michigan comprise nearly three-quarters of the loon population outside of Alaska. Research suggests that loons in Michigan and Wisconsin have rebounded from drastic declines earlier in the 1900s, and the loon population in Minnesota is still thriving. But many threats remain.
Human-caused events are the biggest reason for loons vanishing from many lakes. Development of shorelines and islands for summer homes, campgrounds, and marinas has destroyed traditional nesting areas and other suitable sites. Disturbance of loons, especially during sensitive nesting and chick-rearing periods, can reduce or wipe out loon populations. Pollution of lakes used by nesting loons can lead to buildup of toxins in eggs and young, and the loss of food for chicks and adults.
What kinds of toxins are we talking about? Lead and mercury are two. Where do these toxins come from, and how do they get into loons and other living creatures? Read on for ways to help safeguard loons and other wildlife from toxins--so you can make EVERY day Earth Day!
Going Fishing? Get the Lead Out!
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Challenge Question #13:
"What kinds of things in our environment contain lead?"
(To respond to
this question, please follow the instructions below.)
Mercury Alert!
Lead isn't the only heavy metal threat to loons, wildlife, and water supplies. The mercury found in thermometers, barometers, thermostats, "silent" light switches, fluorescent lamps and blood-pressure gauges is dangerous. Mercury vapor is released when these devices break. These vapors and mercury in emissions from coal-fired power plants and other sources can travel huge distances in the air before falling into wetlands, lakes, and rivers. In the water, it builds up in the bodies of organisms in the food chain. Mercury poisoning affects the nervous system, and any animal--wildlife or human--that eats fish at the top of the food chain may get a big dose. See Journey North's lesson on mercury and its connection to the loon's food chain, and see how to keep hazardous waste in its place:
Then use the information in the lesson to answer:
Challenge Question #14:
"In Little Rock Lake, approximately how many times more mercury do zooplankton have than phytoplankton? About how many times more mercury do fish have than zooplankton? About how many times more mercury do loons have than fish? (For extra credit, make a diagram or chart showing the mercury amounts found at each level of the food pyramid.)"
(To respond to
this question, please follow the instructions below.)
Ask the Expert Now Open
Questions are now being accepted for Loon Expert Ted Gostomski. The deadline is 5 p.m. (Eastern time) on April 27, 2001. Answers from the Loon Expert will be posted on May 11, 2001 via e-mail and on the Journey North Web site.
Scouting a Territory: Discussion of Challenge Question #10
"Why does it make sense for adult loons without territories to make regular visits to territories of breeding pairs?"
Dr. Walter Piper shares what his research suggests: "The fact that loons always rear their own genetic offspring is a key factor. It suggests that territorial intruders--adult loons that lack territories but make regular visits to territories of breeding pairs--seek not to mate with territory holders, but to learn about territories where they might breed in the future. Scouting of this kind makes sense, considering that a loon attempting to breed on a poor territory might fail to produce a single chick for a period of 5 years, while a loon breeding on a good territory might produce 6 or 8 offspring during the same period. Though much work remains to be done, findings suggests that intruders might visit and observe reproductive success on territories in one year and then return to target for takeover territories where chicks were produced the prior year (the reconnaissance hypothesis). If so, then this is an exciting example of systematic and efficient scouting by nonbreeding birds looking for breeding positions. In 2001, I will experiment more with means of capturing nonbreeders and equipping them with satellite transmitters so that we can test the reconnaissance hypothesis through careful monitoring of their patterns of visitation to breeding territories."
Stay tuned! Journey North hopes to bring you updates on the "reconnaissance hypothesis" in the future.
Talking About Takeovers: Discussion of Challenge Question #11
"How do scientists narrow down the possibilities of what intruders are looking for?"
Loon scientist Walter Piper told Journey North how HE narrowed it down:
In order to answer a question like this, one must consider all alternatives systematically. Scientists comb through the possibilities by: 1) using common sense and 2) considering what other scientists have discovered on similar species. Possible explanations are generally termed "hypotheses.
Before describing and evaluating hypotheses formally, it is useful to consider who the intruders are. In most cases, they appear to be nonbreeding loons--that is, loons that lack breeding territories themselves. They are both males and females. We can tell these things because we have marked many nonbreeders either as chicks or adults. The fact that intruders are generally nonbreeders is a useful clue. It tells us that intruders might be seeking territories, which they must have in order to breed. But there are many other possibilities as well.
Hypothesis #1
Intruders might just be looking for food. If so, they should spend much of their time as intruders foraging for food (i.e. diving to pursue fish). In fact, they rarely forage. We conclude that intruders are probably not looking for food.
Hypothesis #2
Intruders might be trying to mate with the pair member of the opposite sex as themselves (i.e. male intruders might be trying to mate with the territorial female, female intruders with the territorial male). This phenomenon is, in fact, the most general explanation for territorial intrusions in other birds, scientists have concluded. By mating with the territorial female, male intruders could produce offspring that they do not have to care for. Females, on the other hand, might mate with males other then their mates in order to increase the genetic quality of their offspring. In any event, we can safely say that loons do not intrude in order to participate in matings with birds other than their own mates, because we conducted a study on this exact issue. We found that pairs stay so close together--especially during intrusions--that there is no opportunity for mating with anyone else. Furthermore, genetic testing of loon chicks showed that, in all cases, the chicks were true genetic offspring of the male and female that reared them.
Hypothesis #3
Intruders might intrude in order to obtain territories. If so, intruders should succeed in driving territorial birds off of their territories, in some cases. They do. Both males and females "usurp" territories by evicting the territorial pair member of the same sex as themselves. What happens is this: An intruder enters the territory and is confronted by the male and female that own the territory. Occasionally, the intruder is able to attack and drive off the pair member of its own sex. Following usurpations, the usurper always pairs quickly with the mate of the displaced bird, and the new pair quickly begins to behave as if they were together always! The displaced bird is sometimes seriously injured by the attack, in which case it may die. More often however, it merely leaves the territory and takes refuge on the nearest unoccupied lake it can find. This is usually within a few km of its original territory. In many cases, displaced owners recover lost territories following the death of the bird that drove them off, or they may even drive that bird off in a later year.
Although we are now rather certain that intruders visit lakes because they seek to usurp the territory, we are trying to learn what features of a territory make it a good territory and therefore one that intruders are likely to try to usurp. Stay tuned!"
Note To Teachers: We'd Appreciate Your Thoughts!
In our May 3rd update, we'll be asking for your feedback on the Journey North program. Watch for our Year-End Evaluation Form and please plan to take the time to send your suggestions and comments. The information you provide at the end of each year is the single most important tool used to guide our planning.
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 #12 (OR #13 OR #14).
3. In the body of your message, give your answer to ONE question.
The FINAL Loon Migration Update Will be Posted on May 3, 2001.
Copyright 2001 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form
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