The first of them are flitting through the Lowcountry - the gorgeous orange "kings" of insects, monarch butterflies. Down the East Coast they migrate in waves each fall.

Spotting the spotted kings

The fall migration of monarch butterflies apparently has begun and usually peaks from mid to late October into November, when they can be found by the dozens if not hundreds on a single roosting shrub.

Here's what to look for:

Monarch butterflies have a wingspan wider than a baseball. They fly like vultures, cruising when they can with the wings in a "V" formation, flapping only when they need to.

Find them in native autumn-flowering shrubs along beachside streets, along beach accesses on Sullivan's Island and other beaches, the old Coast Guard station on the east end of Folly Beach.

Gulf Fritillary butterflies, with bright orange wings, easily are mistaken for monarchs. Their wingspan is smaller, about as wide as a golf ball. They tend to constantly flitter when they fly. Like monarchs, they are drawn to coastal flowering plants and are abundant this time of year.

Various "waves" of migrating monarchs tend to move at the back end of cold fronts when the winds and rain die down, and will gather on the southwest of the islands to wait out winds and rain. The more volatile the weather, the more likely they will move en masse.

But the barrier islands here aren't the heart of the butterfly's range. The Midwest is, and the monarchs are in trouble there - an estimated 90 percent have been lost over the past two decades. The environmental advocate Center for Biodiversity has petitioned the federal government to declare them endangered.

"Monarchs are in deadly free-fall, and the threats they face are now so large in scale that Endangered Species Act protection is needed sooner rather than later," said conservationist Lincoln Brower, considered the leading monarch expert by entomologists.

The petition leaves the regulating agency U.S. Fish and Wildlife Service in the weeds. The crux of the endangered species law is to protect critical habitat, the places the animal needs to survive. For a migratory species like the butterfly, that's a lot of ground.

Each fall monarch flocks make a near-mythic migration from across North America to Mexico and Caribbean islands. The awe-provoking aspect of the trip is that the butterflies migrating this year aren't the ones who made it last year; they are descendants. Butterflies don't live for more than a few months.

Lowcountry beaches are along one of the Eastern flyways, and at the peak of the migration, thousands of the butterflies at a time might be sipping nectar across a single barrier island. What monarchs need to survive is milkweed and other flowering plants routinely cleared from fields as unwanted weeds.

"This is a species whose critical habitat is basically weedy fields, and (protecting it) is going to be very tricky. You're in a situation where you have to maintain weed fields," said Brian Scholtens, College of Charleston entomologist.

U.S. Fish and Wildlife declined to comment for the story.

The reasons the insect is in severe decline are as complex as its life cycle. They include:

The loss of an estimated one-third of its summer breeding habitat, essentially places where weeds grow.

Planting crops that are genetically engineered to resist herbicides that kill adjacent border weeds.

The loss of the wintering population to predators and storms in a small area of Mexico.

The monarch just doesn't sit still and breeds multiple times during a single summer, so protecting a breeding ground - much less a migration route - is a vast enterprise. For example, that one-third of breeding habitat said to be lost has been compared to the size of Texas.

On top of that, there are a lot of monarchs out there. The population appeared to plummet last year but largely recovered this year. The monarchs along the East Coast might be a distinct population from the Midwest butterflies - nobody really knows.

Some monarchs don't migrate, at least not as far as the awe-inspiring flight of the Midwest insects to Mexico each year. Wildlife ecologist Billy McCord, of James Island, has documented that at least some monarchs appear to winter in the Lowcountry each year.

Even tracking their movement is an issue. McCord has tagged some 22,000 monarchs in his 18 years of work, trying to determine just where East Coast monarchs migrate. He's gotten reports of only a half-dozen or so sightings in Florida, one in Mexico.

But the decline is as apparent as the swaths of border plants cleared to develop the barrier islands. Monarchs moving through the Lowcountry prefer a shrub called groundsel bush, sea myrtle, or saltbrush. It grows along the edge of marshes and is cut to open marsh views.

"Most of the monarchs are going to that plant," McCord said and he's watched site after site disappear over the years.

The Fish and Wildlife Service has 90 days to determine whether the petition is valid enough to call for further review, essentially to decide if there is enough of a decline demonstrated to warrant further investigation. A denial can be challenged in court. A go-ahead could further pry open a large can of worms.

The service in July controversially designated critical habitat for the loggerhead turtle, another migratory species. That habitat covered 700 miles of beaches and nearly 300,000 miles of ocean along the Southeast and Gulf of Mexico, including more than 79 miles of shoreline in South Carolina. The decision came after a petition by environmental advocates.

What to do about large-swath critical habitat for migrating species "is something they're going to face over and over as more 'iconic' species like the monarchs get into trouble," Scholtens said.

Meanwhile, there's both a commercial and an educational value to monarchs - both of which could be curtailed by an endangered species designation. A more effective way to sustain the butterfly might be to educate the public better about the value and need to foster plants like milkweed, Scholtens said.

Reach Bo Petersen at 937-5744, @bopete on twitter or Bo Petersen Reporting on Facebook.