As monarch butterflies pause along the south coast before setting off on their perilous migration to Mexico, a few are picking up luggage for the long flight.

Armed with nets, researchers are catching some of the orange and black beauties and tagging them in hopes of learning where their migration takes them.

It is work that requires a most steady, gentle hand, says Lauren Miller-Donnelly who is leading this work from Mass Audubon’s Allens Pond Wildlife Sanctuary.

“The most important thing is not to harm them in any way … after all, they have a very long, difficult flight ahead of them and the last thing we want to do is make it any harder,” she said.

Last week found Ms. Miller-Donnelly near the water’s edge with field biology students from Bristol Community College there to learn how to tag butterflies.

Although monarch numbers have plummeted throughout the region, here they were easy to find as they massed in wait for a good northerly breeze to send them south.

Being careful starts with netting the butterflies, she said. There’s a trick to catching them with an upward swoop of the net when they are on a flower, distracted and drinking nectar — “You don’t want to just flail away at them in the air.

Helping the researchers is the fact that monarchs have more robust wings than most butterflies, but it is still easy to damage a wing, leg or antenna.

They then carefully grasp the monarch by the body and keep the wings folded together to prevent flapping as they remove it from the net.

“Then comes the trickiest part,” attaching the tiny white tag to the center cell of the right hind wing.

You develop a method, Ms. Miller-Donnelly said. She favors using a fingernail to pry the sticker-like tag from its backing and then pressing the tag against the wing.

The tags are virtually weightless and don’t impede the monarchs’ ability to fly at all, she said.

On each sticker is a code — three letters, three numbers. And instructions ask anyone who finds the butterfly and tag to contact 1-888-tagging or email the information to tag@ku.edu

That gets the information to the University of Kansas Monarch Watch, an organization dedicated to learning about and protecting the butterflies — monarchwatch.org

Putting the tags in the same place makes it easier for researchers in Mexico to spot the little white dots. They then net the butterflies, record the information, and send them on their way.

“The data from these recaptures are used to determine the pathways taken by migrating monarchs, the influence of weather on the migration, the survival rate of the monarchs, etc,” says Monarch Watch. The more that is learned about them, the better the chances of helping their survival.

Many perils await the butterflies as they head south, Ms. Miller-Donnelly said. They can be driven off course by storms — really big storms can devastate a migration. And they need constant refueling from favorite fall flowers like goldenrod and butterfly bush.

She said some of those setting off hatched a month or more ago; others may only have hatched within the past day or two.

Because it is devoted to monarch butterflies, Monarch Watch is also a defender of milkweed, the only plant on which monarch caterpillars can survive.

“Monarch butterfly populations are declining due to loss of habitat,” says Chip Taylor, director of Monarch Watch. “To assure a future for monarchs, conservation and restoration of milkweeds needs to become a national priority.” The group even gives milkweed plants away to those who can put it to good use.

Ms. Miller-Donnelly said monarchs are doing better in the Westport, Little Compton, Dartmouth area in part because large areas of open land have been preserved and are lightly used — frequent mowing also cuts down milkweed.

Planting milkweed is one way to help, she said, but is most effective when large patches can be created (the butterflies are much less likely to discover individual plants),

“For people with normal size yards, probably the best way they can help is to provide the flowers butterflies like,” she said, “especially those flowers that bloom in late summer and early fall.”