The Fall Migration
still other monarchs start along the Atlantic Coast and fly southwest North American monarchs make up toward Texas. A few monarchs on two fairly distinct populations (with each of these routes don’t fly all the some geway to Mexico, instead staying to netic inwinter along the Gulf Coast. terchange Butterflies often use thermals between (updrafts of warm air) during their the two) fall migratory flight to save energy, separated and fly at a pace of about 25-30 roughly by miles per day. These well-traveled the Rocky butterflies spend the winter clustered Mountains. together on the trunks and branches In the fall, of Oyamel Fir trees, in a low-enerbeginning gy, non-reproductive state that biprimarily ologists refer to as “diapause.� They in mid-Au- survive using stored fats produced gust, you from the milkweed they consumed are likely as caterpillars and the nectar they to see mon- drank from fall-blooming plants archs from during their flight to Mexico. They the eastern keep warm by clustering together population so densely that tree branches bend migrating from their weight. south towards Mex- The Spring Migration and Summer ico, where Breeding Season they will spend the winter in high elevation These same monarch butterflies Oyamel Fir forests. A central migra- begin their return trek northward tory route involves monarchs from from Mexico in March. Now, the locations in the Upper Midwestern focus is finding milkweed on which U.S. and southern Canada, while to lay their eggs. As early as the secPage 23