Monarch Butterflies Why Do Daily Monarch Counts Go Up and Down? Analyzing Data From a Fall Migration Roost Contributed by Paul Viger, Campbell, Minnesota During fall migration, some lucky people have thousands of monarchs pause in their yards at overnight roosts. Mr. Viger of Campbell, MN is one such person. Each day he counts the monarchs, tags them, and records information about the wind and weather. As they do each year, the monarchs stayed for almost 3 weeks in fall 2001. He watched their numbers rise and fall each day, and noticed an interesting pattern. You can see it too if you look carefully. What might be causing the daily changes? (Click graph for a larger version.) Try This! Either print a copy of the graph or make your own using Mr. Viger’s data. First, spend some time looking at the graph. What do you notice? Next, look carefully at the wind direction Mr. Viger noted each day between Aug. 27 and Sept. 6. For each data point on your graph, write the wind direction beside it. Now describe the relationship you see between wind direction numbers of monarchs. What do you think is happening? Explain why you think monarchs might behave this way. Can you find the tagged butterflies resting in the Viger's roost? By the way says Mr. Viger, "This picture of my two kids (Alex age 5 in 1991 and Emily age 3) has an interesting story. We tagged a few butterflies in the morning and I told the kids to bring their last ones to the house and I would get a picture. One of those butterflies was recovered in Mexico. It's neat to have a picture of a butterfly (I'm not sure which one) that made it to Mexico." Facebook Pinterest Twitter © 1997 – 2019 Journey North. All rights reserved.