Starting in September and October eastern and northeastern monarch butterflies begin their migration from Southern Canada and the United States to Central Mexico in what is described as one of the most spectacular natural phenomena in the world. Monarchs fly south using several flyways then converge in Central Texas to form a single flyway the remainder of their migration. In March, they start their return trip arriving back north around July.  What is truly amazing is that no single butterfly will make the entire round trip. 

Monarchs only travel during the day so they need to find a roost at night.  When they roost they gather close together during the cool autumn evenings. Tens of thousands of butterflies can roost in a single tree.  Ideal trees for roosting are pine, fir and cedar trees as they have thick canopies that moderate the temperature and humidity at the roost site.  In the mornings, the monarchs will bask in the sunlight to warm themselves.

Monarchs overwinter in the same 11 to 12 mountain areas in the States of Mexico and Michoacán from October to late March.  They roost for the winter in the oyamel fir forests at elevations of 2400 to 3600 meters (nearly 2 miles above sea level). The mountain hillsides of the forest provide an ideal microclimate for the butterflies.  Temperatures there range between 0 and 15 degrees Celsius.  With a lower temperature the butterflies would need to use their fat reserves. The humidity in the forest assures the monarchs won’t try out which allows them to conserve their energy.

The monarchs know their way to the overwinter sites even though this migrating generation has never been to Mexico before.  While researchers are still investigating the directional aids used by monarchs to find their overwinter location, it appears to be a combination of magnetic pull of the earth, the position of the earth and other aids. 

The western populations of monarchs which are those west of the Rocky Mountains have a similar migration only they overwinter sites on the coast of California.

There are monarch migration sites which will show sightings for Summer and Fall of 2016 and give projections as to when peak migrations will occur.  There are also multiple festivals and events that celebrate this beautiful migration of the monarch butterfly.  In Grapevine, TX, the Butterfly Flutterby is being held on October 15 between 10 a.m. and 2 p.m. This is an event for the entire family so come out to Grapevine Botanical Gardens for the Butterfly Flutterby.