Common Loon Migration Update: March 25, 1999
Today's Report Includes:
Loons Starting to Migrate!
Most lakes in southern states stay open all winter. It might seem as though some loons would winter on them, but they virtually never do. Lakes that freeze every year often have fewer plants and fish than those that have enough warmth and sun for a year-long growing season. Warm lakes are great for wintering herons and egrets, but not for loons. Why not?
Reappearing Like Magic!
Challenge Question # 5
"How do so many loons manage to time their arrival on their breeding lake for the very day that the ice goes out?"
Discussion of Challenge Question # 2
The seventh graders at Iselin Middle School explained this well and very concisely: "Loons grow and lose all their feathers at once because if they grew one or two feathers at a time the loons cannot fly. They are completely flightless without every single one of their feathers."
Loons have relatively heavy bodies and small wings--both adaptations for diving deep into water. With a complete set of flight feathers, their wings have just about the minimum amount of surface area to hold up their bodies. Missing even one or two feathers, their wings may not support their bodies, so to minimize the time that they are flightless, they molt all the feathers at once.
Discussion of Challenge Question # 3
"Which one of the loon vocalizations (hoot, wail, tremelo, yodel) do you think can be heard on the wintering grounds? Explain your reasons."
Several students used excellent reasoning to tackle this question. First and second graders Julie, John, Krista, and Stephen figured it this way: "We think that the you can hear the hoot on the wintering grounds. We know it isn't the tremelo because that is a warning sound you hear when people approach the nest. The yodel is to attract a mate so that would be a spring sound. We have heard the wail in the summer here in Vermont. So it has to be the hoot."
Dr. Judith McIntyre wrote in her book, The Common Loon: Spirit of Northern Lakes, "Hoots are about the only call used during the winter, but tremolos and yodels can be heard infrequently. Loons apparently are competent to perform all calls in their repertoire at any time of the year, but are not in physiological condition to do so." Changes in hormones are important influences on loon calls just as they're important influences on other territorial and breeding behaviors.
How to Respond to Today's Challenge Question
Please respond to only on Challenge Question in each e-mail response.
The Next Loon Migration Update Will be Posted on April 8, 1999
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