Jim Gilbert
Monarch Butterfly

Today's News
Today's News

Spring's Journey North
Spring's Journey North
Report Your Sightings
Report Your Sightings
Teacher's Manual
Teacher's Manual
Search Journey North
Search Journey North
return to:
JNorth Home Page
A/CPB Home A/CPB

Challenge Question #13

John McLain (jhmclain@exis.net)
Tue, 19 May 1998 11:41:37 -0400

In Challenge Question #13, you asked, "Look at the areas where no monarchs
have yet been reported. What might explain the lack of sightings there? How
do you think the geography of North America might be affecting the
migration? What other factors might explain this spring's migration pattern?"

There definitely appears to be two, possibly three,'highways or gathering
spots' in North America. A number of things could cause this.
1. Presence, or more likely absence of water (Mississippi, Missouri, etc.
leading north and westward. Chains of rivers and lakes leading NE from the
Gulf of Mexico
2. Mountain chains - Appalachian/Blue Ridge Mountains forming a chain of
valleys such as Roanoke and Shenandoah leading north and east. These
valleys funnel, protect, warm, and provide nectar and food supplies as well
as water.
3. Impact of the jet stream at altitude and its impact on the lower winds.
Note how it bulges and ripples northward and eastward during the summer
months.
4. Impact of heavy rains in localized areas leading to 'avoidance routes'.
(I've noticed that I see fewer butterflies, particularly the larger
varieties such as monarchs, in my backyard on rainy, cloudy, or cooler
days. Right now the weather in the central and SE portions of the country
has been wet.
5. Presence or absence of nectar and food plants could lead to
congregation areas.
6. Climate - assuming they are attracted to warmer locales. They would
tend to go east or westward at firs then north as the climate warms to the
north. The jetstream also 'pushes' eastward.
7. Do monarchs tend to return to the area where they were hatched
(instinct)? Do they band or otherwise mark monarchs? A major challenge
considering their lifespan and size. Would marking them with dyes impact
their flight characteristics?
8. Past weather impacts - if monarchs return to an area by instinct, what
part did the severe weather of several years ago play on the current
migration routes. You've got to survive to reproduce
9. Just as an observation, many migratory birds follow similar routes, for
example -- the Atlantic flyway.

This was a fun question. Thanks for the stimulation.

Mary McLain from jhmclain@exis.net
John H. McLain
Eagle Systems Inc
468 Viking Drive
VA Beach, VA 23452
Vox: 757-498-5673
Fax: 757-498-5683
email: jhmclain@exis.net