|The migration's leading edge is now moving along the Sierra Madre Mountains on the final 400 miles of the journey. Thanks to Rocio Treviño and her network of observers for sending news from this region.
Major Monarch Highway
The Sierra Madres form a chain of north/south peaks and valleys that stand in the path of the easterly winds which predominate at this time of year. As the winds strike the mountains, the butterflies get a lift.
Nuevo Leon: "I'm watching the passage of the marvelous monarch butterflies. As I counted 100 in 30 minutes I wished them luck on their travels and a safe return."
October 28, 2013 Iturbide, Nuevo Leon
Only 300 Miles to Go
The largest roost—and southernmost report of peak migration—came from a valley only 300 miles from the overwintering region.
Tamaulipas: "Thousands of monarch butterflies rested in a large mesquite. They fed in a field filled with false sunflowers. According to the local people, these butterflies had been at the site at least four days awaiting a strong north wind to migrate south."
October 26, 2013 Juamave, Tamaulipas
A Million Monarchs
The migration is so concentrated in the Sierra Madres that monarchs go through at exceedingly high rates. This is where the most spectacular sightings are possible. You might see a million monarchs one day— and none the next—in the very same place. Dr. Bill Calvert experienced a chance encounter one October.
"It was just absolutely phenomenal. Between 11 and 12 o'clock monarchs were passing overhead by the millions. They continued pouring over until about 1 o'clock. Seeing a million butterflies passing over is kind of magical."
October 17, 2004 Cumbres de Monterrey, Nuevo Leon
Ready and Waiting
Children at the overwintering sites are eager to announce the arrival. One boy promised Estela:
"I will pass by your family's store on the way to school and tell you the moment I see the first ones arriving!"