A loud, trumpet-like call sweeps across acres of tall grass fields at the Patuxent Research Refuge in Laurel.
The call, made by a male whooping crane, is quickly followed by a shorter, two-note call from a nearby female.
"That's the unison call," said Charlie Shafer, a biological technician at the U.S. Geological Survey's on-site Patuxent Wildlife Research Center.
The unison call is how the majestic North American birds got their name, Shafer said. It's also a sign that breeding season has begun at the largest whooping crane captive breeding program in the nation.
In 1966, the U.S. Fish and Wildlife Service's Patuxent Wildlife Research Center created the program to help preserve the endangered whooping crane population. Since then, staff and volunteers at the program — now run by U.S Geological Survey researchers — have raised more than 1,000 whooping crane chicks, teaching them how to eat and drink, taking them on walks and preparing them for release into the wild.
"We're kind of like proud parents," said Ken Lavish, a Burtonsville resident and volunteer through the Friends of Patuxent, a nonprofit organization that supports both refuge and research center. "The main reason we're here is to get them out into the wild."
"And getting them away from the 'E' word — extinction," said Diana Ogilvie, a Bowie resident and visitor services park ranger and volunteer coordinator at the Patuxent Research Refuge.
The refuge will celebrate whooping cranes throughout the month of May as Friends of the Patuxent's Adopt A Whooper committee hosts "Magnificent Whooping Crane Month," a series of free exhibits, interactive activities and presentations about the endangered birds.
Captive breeding program
Whooping cranes, the tallest North American bird, are known for their white feathers, black wing tips, fully extended neck and legs and elaborate courtship dance.
"The birds are so charismatic," Ogilvie said. "They're as tall as you are, their wing span is 8 feet, they dance and they're so beautiful."
But in 1937, fewer than 20 of them remained. The population began to sharply decline in the 1800s due to hunting, man-made changes to their wetlands habitat and feather and egg collecting.
"It's almost our fault that they're endangered," Shafer said. "I feel like it's also our responsibility to bring them back."
To increase flock numbers, Patuxent launched its captive breeding program at the refuge with 12 eggs collected from the wild. Today, the Patuxent flock has more than 70 whooping cranes. Of that total, there are about 25 breeding pairs that lay an average 40 eggs during the May-through-July breeding season.
The average Patuxent whooping crane clutch, or number of eggs per nest, is two. If researchers remove both of the eggs, the cranes often lay another set in about 10 days.
To help keep the removed whooping crane eggs warm, sandhill cranes living at the research center lend their body heat and act as surrogate incubators for the first 20 days, Shafer said. Researchers use mechanical incubators for the last 10 days. These eggs are hand-reared, meaning they are raised early on by biological technicians and volunteers.
A smaller number of eggs are raised by the whooping cranes, or parent-reared, and left to captive parents for warmth, care and feeding.
This year, the research center's first hand-reared egg is due to hatch around May 8.
As soon as a hand-reared chick can see outside of its egg, research center staff and volunteers wear "crane costumes" — white, poncho-like outfits and hoods that cover the entire body. Staff and volunteers can see through the hood's camouflage netting, but their faces are disguised. The chicks "imprint" on the costumes, meaning they bond with the costumed figures as if they were parents.
"You want to disguise the human form so they're not comfortable with humans," Ogilvie said.
While wearing these costumes, staff and volunteers use a hand-held puppet head resembling a mature whooping crane to feed the newborn, cinnamon-colored chicks crumbled food.
"What we're trying to do is duplicate what the parents do," Ogilvie said. "They're fast learners. Some learn in one day to go to the bowls to get food and water."
Staff and volunteers also take the chicks for walks, using the puppet head to show them mealworms and playing brooding calls like their parents would.
Sometimes, the volunteers even walk into water with them.
"I went into the pond, walked around and they followed me," Lavish said. "…They need to learn that that's their habitat."
In addition to learning from those in crane costumes, each chick observes a neighboring adult whooping crane, eventually modeling its behavior.
The chicks grow up to an inch a day and are moved to large, outdoor pens when they are about 25 days old. By day 70, they are moved into even larger pens to prepare for life in the wild.
The parent-reared chicks are eventually released on the Necedah National Wildlife Refuge in Wisconsin.
But before the breeding season's earliest hand-reared chicks are released, they must learn the migration route, Shafer said. Around day seven of a chick's life, they meet the "ultralight trike," a yellow aircraft with white, hang glider-like wings. A costumed pilot operates the ultralight, driving in circles and dropping meal worms along the way, he said.
"The chicks learn, 'If I keep following this thing, I'm going to get a good reward,'" Shafer said. "It's positive reinforcement."
The pilot and pseudo-parent at the controls also helps, Shafer said.
In October, the cranes leave the refuge and learn the migration route by following a similar ultralight, run by Canada-based Operation Migration, from Wisconsin's White River Marsh State Wildlife Area to Florida's Gulf Coast.
Most of the breeding season's later chicks are released into a non-migratory flock in Louisiana.
In recent years, the research center has expanded its efforts beyond hatching and releasing to include nesting habits of the released birds and threats to their unborn chicks.
Someday soon, Shafer said, he'd like to see a thriving whooping crane population in Wisconsin, with healthy chicks being born regularly.
"We want the population to be self-sustaining," he said. "It's a constant progression. Eventually, we'll get there."
Magnificent Whooping Crane Month events take place on Saturdays and Sundays throughout May at the refuge's National Wildlife Visitor Center, 10901 Scarlet Tanager Loop. Kids' Day on May 9 is 10 a.m. to 2 p.m. and will include puppet shows, story times, a migratory bird puppet craft and a scavenger hunt. The refuge also offers whooping crane observatory tours throughout the year. For more information, go to friendsofpatuxent.org or call 301-497-5887.