“I will never forget watching a female Monarch flutter over a field that appeared to be a sea of green foliage. She tirelessly touched plant after plant, but placed her eggs only on milkweed.”

This experience some years ago awoke in author Paulette Haywood Ogard the understanding that butterflies have specific preferences for what they allow their babies to eat.

The orange and black Monarch butterflies — which have begun returning to Alabama over the past week or two — sample the nectar of practically any available flower, but when it’s time to lay eggs, only milkweed will do.

When the cute, striped Monarch caterpillars hatch and begin eating the milkweed leaves, they take in certain chemicals that can cause heart failure in vertebrates — but that will protect them throughout their lives. A bird that eats one Monarch caterpillar or adult is unlikely to try another.

Birds quickly learn to avoid Monarchs and any other butterflies or caterpillars that look like Monarchs, writes Ogard in her book Butterflies of Alabama. Ogard, a 1973 graduate of Jacksonville High School, co-authored the butterfly guide with Sara Cunningham Bright.

While each butterfly species has its own preferred host plant, several species benefit from the Monarch’s choice of food, even butterflies that can’t eat milkweed.

Alabama has at least six native milkweed species, including the showy Butterfly Weed, with its pannicles of bright orange flowers and dark green spear-shaped leaves. This butterfly magnet can be found growing along unkempt roadsides as well as in open fields and in the woods on Mount Cheaha.

Another native milkweed, Swamp Milkweed, with broad leaves and a topknot of waxy, white flowers, pops up in the most unexpected places — one plant lived for years at the edge of the woods between the Anniston Star and the Anniston Museum of Natural History.

With all the native milkweeds and others that gardeners have introduced, Monarchs have little problem finding host plants on which to lay their eggs when they come through Alabama in the spring and fall.

“Monarchs are such familiar butterflies that I also have to remind myself that here in Alabama, we primarily see (them) only during their migrations — in the fall, as they move toward their Mexican wintering grounds, and again in spring, as they return northward,” Ogard said Tuesday. “From now through November is Monarch season in our state.”

Ogard said she began seeing Monarchs in her yard in Birmingham this week and she expects the numbers to increase through October.

“Had a couple in my yard today,” she said. “When I was in upper New York a couple of weeks ago, they seemed to be everywhere! I have now begun to see reports that folks in North Carolina and Tennessee are observing Monarchs in numbers, so they should be passing through Alabama soon.”

The Monarchs now in central Alabama are on their way to Mexico. Many won’t make it, but the females will lay eggs all along the route, and after about a month, the next generation will mature and those butterflies will head south, too.

“Once in the high mountains of central Mexico,” Ogard writes, “Monarchs cling by the millions to fir branches, occasionally nectaring on warm days, but primarily living off stored fat reserves.”

With the total Monarch population in decline for the past decade, the butterflies in this year’s migration need all the sustenance they can get for their journey south. After the Monarchs leave Calhoun County, they’ll have to fly another 2,000 miles to get to the Mexican state of Michoacan.

After spending the winter at the Monarch preserve, the butterflies mate and many die. Those that survive join the new generation on the northward migration in March.

The Monarch is not an endangered species, or even officially threatened, but biologists tracking their migrations have noted that the number of Monarchs has been falling steadily. This past winter, the multinational team reported in “Insect Conservation and Diversity” that clusters of overwintering Monarchs were the smallest since the team began collecting data in 1994.

The Mexican government has protected the Monarchs’ overwintering grounds, and an international coalition of butterfly enthusiasts, ecologists and environmentalists is working to reforest the denuded mountains outside the reserves. Other possible contributors to the decline could be shrinking summer habitat in the United States and Canada, agricultural pesticide use and global climate change.

The arrival of the Monarchs in Alabama in both spring and fall is a little-understood natural wonder. As Ogard writes, “Monarchs tickle our fancies and capture our imaginations, perhaps because — from poison-eating caterpillar to continent-navigating butterfly — they seem to routinely accomplish the impossible.”

Geni Certain is the editor of The Daily Home in Talladega, sister newspaper of The Star.

Butterfly weekend

• JSU Field School weekend includes a program for pre-schoolers, lessons on identifying butterflies and a photographic butterfly safari.

• Sept. 23-24 at Little River Canyon Center and DeSoto State Park in Fort Payne.

• All activities are free.

• For more info, contact JSU Field Schools, 256-782-5697.