Colorado Parks and Wildlife biologists wrapped up a grueling month spent trapping lesser prairie chickens on their breeding grounds - also known as leks - in five counties of western Kansas. It was part of a four-year effort to re-establish the colorful birds on their native sand sagebrush and grasslands in Colorado.

The CPW wildlife biologists, led by Jonathan Reitz and Liza Rossi, worked seven days a week, rising well before dawn each day and sitting for hours in blinds, shivering in the dark in below-freezing temperatures, to catch lesser prairie chickens.

The biologists used large, remotely controlled drop nets and traps to catch the birds. They hid on the perimeter of the breeding grounds and waited for the birds to arrive at dawn and begin their courtship rituals.

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CPW wildlife biologists, led by Jonathan Reitz and Liza Rossi, erected large electromagnetic drop nets above lesser prairie chicken breeding grounds, known as leks. They worked in the dark, often in temperatures below freezing, and then hid in camouflaged blinds on the perimeter of the lek to wait for the birds to arrive at dawn. Courtesy CPW / Bill Vogrin.

Male lesser prairie chickens put on dramatic displays to attract a hen. They will establish a territory on the lek, then bow, drop their wings and raise pinnae feathers on their necks, bringing them to a point behind their heads as they challenge other males.

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Two male lesser prairie chickens spar in a mock battle as they try to display dominance in their effort to win a mate. Courtesy CPW / Bill Vogrin.

The males can be heard stomping their feet in a mating dance, and they boom by inflating a red sac on their neck and quickly releasing the air. They also make a loud cackling noise as they engage in mock battles, flying into the air and confronting rivals on the breeding grounds.

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Male lesser prairie chickens can be heard stomping their feet in a mating dance, and they boom by inflating a red sac on their neck and quickly releasing the air. They also make a cackling noise that can be heard as they engage in mock battles, flying into the air and confronting rivals on the breeding grounds. Courtesy CPW / Bill Vogrin.

When they wandered under the net, biologists dropped it and raced to the lek to secure them. The birds were bagged and taken to a field lab where the biologists weighed and measured them, tagged and banded them before driving them 3 1/2 hours to southeast Colorado for release the same day. The team also released chickens in far southwest Kansas to rebuild populations there.

Now, the biologists will spend the summer months monitoring newly established Colorado leks and nests to determine if the rare and vulnerable birds are taking up residence or have flown the coop for home.

It's an ambitious plan to restore lesser prairie chickens, which once numbered in the tens of thousands in Colorado but had mostly disappeared in recent years.

The CPW team, led by Reitz and Rossi, worked in collaboration with the Kansas Department of Wildlife, Parks and Tourism, Kansas State University and the U.S. Forest Service.

The target recovery area is a 330,000-acre swath of sand sagebrush and grasslands straddling the two states including the Comanche National Grassland in Baca County, Colorado, and the Cimarron National Grassland in Morton County, Kansas, as well as privately owned rangeland and Conservation Reserve Program grassland. Both the Comanche and Cimarron grasslands are owned and managed by the U.S. Forest Service.

Historically, the region was home to large flocks of lesser prairie chickens. But the conversion a century ago of grasslands to cropland, and the resulting Dust Bowl in 1932, wiped out many of the birds.

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Each bird is examined for illness, injury and age. Here, wing feathers are measured and studied for an age estimate of the bird. Courtesy CPW / Bill Vogrin.

More recently, the lesser prairie chicken population was devastated by severe snowstorms, particularly in December 2006, followed by years of drought. By 2016, biologists counted just two males on the Comanche and five males on the Cimarron.

Over the past four years, Reitz and Rossi have relocated 103 males and 102 females to the Comanche. The team also released 101 males and 105 females during the same time period just east of the state line in Kansas, making this the largest known translocation effort for lesser prairie chickens.

But re-establishing populations isn't as simple as catch-and-release. Reitz and Rossi discovered the birds often don't easily adjust to their new surroundings.

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A lesser prairie chicken hen shows off her radio collar, identifying leg band and color-coded leg bands prior to being released. Courtesy CPW / Bill Vogrin.

"They often take flight upon release and can travel great distances," Reitz said. "We've observed some traveling 60 miles or more from the release site."

The CPW team knows exactly how far some travel because they attached monitoring devices to the chickens before their release. Most got beacons that allow them to be tracked by radios using a special antenna. Others were fitted with solar powered, GPS backpacks that transmit the chickens' location 10 times a day. CPW expects to monitor them for the next two years.

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Some lesser prairie chickens were equipped with solar-powered GPS backpacks that are designed to transmit their location 10 times a day for the next four years. Already, chickens released with the GPS devices in previous years of the project have been tracked as far away as Texas. Courtesy CPW / Bill Vogrin.

"We know some birds flew to Texas and Oklahoma," Reitz said. "It's not uncommon for them to take off upon release and fly great circles before eventually returning to the release spot and settling down."

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CPW wildlife biologists April Estep and Rebecca Schilowsky release lesser prairie chickens from boxes after they were captured in western Kansas. Each bird was weighed and measured, examined by a veterinarian, given an identification bracelet and color-coded bands and outfitted with a tracking device so biologists can track them in coming years. Courtesy CPW / Bill Vogrin.

And that leads into the next phase of this wildlife conservation effort.

"Our technicians will track them on the ground as the birds spread out," Reitz said. "We will use an airplane to find them and point our technicians in the right direction. We want to know if hens are nesting and whether they succeed in hatching chicks."

In the past when Colorado had few chickens, biologists were employing some high-tech devices to trick the roosters into staying. CPW deployed "call boxes" programmed to play cackles and other sounds to entice male lesser prairie chickens to stay on a lek.

This year, however, CPW is releasing birds on an active lek for the first time. The goal is for them to join birds from the previous year's translocation efforts. Biologists are hopeful the chickens will stick around.

A doctoral candidate and three master's students from Kansas State area have been assisting with the data collection and analysis.