MISSION, Texas (ValleyCentral) — When cold fronts blow south across Texas this fall, look up and you just might be able to spot glimpses of monarch butterflies.

These beautiful migrators travel southward in the fall primarily by sailing upon winds provided by strong cold fronts.

“Monarchs do not flap their wings in vigorous flight for migration,” said Mariana Trevino-Wright, executive director of the National Butterfly Center in Mission, Texas. “They sail on those cold fronts, typically riding a wind current at about 300 feet up in the air. They do that for efficiency.”

This knack for efficient travel helps explain why the monarch’s orange and black wings span approximately 4 inches — larger than many other species of butterflies. They need these large wings at those heights to take advantage of air currents and to avoid having to expend energy to fly around obstacles, trees, buildings and homes.

“[A migration} looks like a dark river in the air,” Trevino-Wright said. “If you’ve got binoculars, go grab those and you can see that it is butterflies–and not just any butterflies, but monarchs.”

This photo shows a monarch butterfly in flight
In this Aug. 28, 2019 file photo, a monarch butterfly flies to a nectar plant, in Freeport, Maine. (AP Photo/Robert F. Bukaty)

The fall migration has likely already started

The Lone Star State’s official insect, monarchs migrate in two waves typically first appearing in the northern areas of Texas in late September or early October in conjunction with the first cold fronts of fall.

“It may be a week or two before that, depending on the sort of cold front activity we have this fall. It could be later than that,” Trevino-Wright said. “That first wave of monarchs that pass through the central US flyway, which is mainly Texas, typically hits the Gulf coast around Columbus Day.”

The butterflies will travel as much as 30 miles a day and will typically arrive in deep South Texas and the Rio Grande Valley at the end of October, around Halloween and Nov. 1, which is Dia de los Muertos, the day of remembrance of the dead in Mexican tradition.

The migration continues south to Michoacan in southern Mexico, where the butterflies roost in a dormant state during winter.

Where are the monarchs now?

To find monarchs in your area, keep a watch on areas — even backyards — that have the plants they most love: milkweed.

This plant is the only food source for monarch caterpillars, which feast upon the leaves that remain toxic to other insects and animals. The adult butterflies also land upon the milkweed to drink nectar from its blooms, clusters of star-like flowers that usually range from yellow, orange to red in Texas.

On Oct. 3, monarchs were spotted in several Texas communities, including Allen, Plano, Rockport, and Canyon Lake, near Austin. However, on that same day, monarchs were still being reported as far north as Chicago, Illinois, and Minneapolis, Minnesota, according to monarch-tracking data provided by JourneyNorth.org, which documents the sightings during the fall.

Because monarchs migrate in large groups, another way to track migrations is to use radar, just the kind your local meteorologists use to track weather patterns.

“Your meteorologists might give you a hint that some big movement is on the way,” Trevino-Wright said.

Not all monarchs migrate — that makes these special

It’s a myth that all monarchs migrate. The monarch butterflies that pass through Texas are among special population of butterflies that migrate, spending winters in Mexico and traveling north as far as Canada during the warmer seasons. However, not all monarch populations migrate — nor do they even need to do so.

“As an example, the island of Puerto Rico has monarchs that do not migrate,” said Mariana Trevino-Wright, executive director of the National Butterfly Center in Mission, Texas. “They have no need to — the climate is perfect year round. And other places around the world have monarchs that do not migrate. In some places, they might make a regional migration, or a seasonal movement that’s not really a migration.”

The difference in monarchs turns out to be important when understanding conservation issues facing the North American migrating species. While, the monarch butterfly is not endangered globally, the migrating species passing through Texas is at risk, being classified in July as endangered by the International Union for Conservation of Nature.

“[Monarchs are] a globally secured species,” Trevino-Wright said. “What we may see in our lifetime is not the end of the monarch but the end of the transcontinental monarch migration, which is unique to the northern hemisphere of this continent.”

Loss of habitat caused by urban sprawl and weed-fighting chemicals used in agriculture are commonly cited threats to the migrating butterfly. Texans can help counter these threats by planting milkweed, which provide food for the monarch caterpillar as well as flower nectar for the butterfly.

This photo shows monarch butterflies roosting
In this Nov. 7, 2005 file photo, monarch butterflies roost at the “butterfly grove” in Pacific Grove, Calif. (Vern Fisher/ Monterey County Herald via AP, File)

When winds change, butterflies will roost

As needed, the butterflies will roost in parts of Texas, as cold fronts fizzle or warm winds blow from the south.

“Roosting is not really sleeping,” Trevino-Wright said. “They are not sleeping like humans. They are in a sort of suspended state of animation, almost like hibernation, where their body temperature cools and their metabolism slows down along with all their systems. So it’s like hibernation but overnight.”

Roosts have already been spotted in San Antonio Sept. 30 and in both Kress and Wichita Falls on Oct. 2, JourneyNorth.org data indicates.

Roosting monarchs will stay put in these areas for as long as they lack the winds from a cold front to continue an efficient migration south. Because of this, some communities will be able to enjoy large populations of monarchs for days or weeks, as the butterflies feasting off the nectar of flower plants.

“If you’re lucky enough to have monarchs en masse, congregating on your ranch or in a city park — normally they’ll look for stands of trees to do this — don’t put the word out to people who may not be respectful of wildlife,” Trevino-Wright said. “Enjoy the spectacle. It’s beautiful. People describe it as a magical or spiritual experience to see great numbers of them roosting, dropping from the trees, sailing, flying around together. You know, it’s like air ballet.”