NATURE NOTES: Pulse of the Desert Plains: Tracking Grassland Birds on the Marfa Plateau

Originally broadcast on Marfa Public Radio on February 15, 2018
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By Andrew Stuart

It’s dawn in late January, near Marfa, and the grasslands on Mimms Ranch are radiant, swaying like a thick, golden mane in the sporadic breeze.

Across the plateau treks a 20-person team – scientists, birders, volunteers.

A pair holding radio antennas leads the way. Soon, they locate a signal. Technicians swiftly raise a net – and the rest of the group moves into formation, creating a semicircle.

Quietly, they advance, closing in on the signal’s unseen source.

Suddenly, it rises, in a flurry: a tiny grassland sparrow. The bird darts skyward – and then flies just outside the net.

It’s a narrow miss. But as the morning continues, this team – led by Alpine’s Borderlands Research Institute – will catch half a dozen Baird’s and grasshopper sparrows. The Marfa grasslands – some of the Chihuahuan Desert’s most pristine – provide these birds with something they need, that’s increasingly hard to find: a winter home.

“Grassland specialists” like Baird’s and grasshopper sparrows generally escape notice. That’s to their benefit. Flight exposes them to predators, and they’d sooner run than fly.

Small and secretive, yes, but also remarkable. The sparrows travel from nesting grounds in Montana, North Dakota, Canada – journeys of more than 1,500 miles. Grasshopper sparrows are distributed across the continent. But the Baird’s winter range is centered on the Chihuahuan Desert. The Marfa Plateau is its northern limit.

And it’s been a tough stretch for the two birds. Since 1966, their populations have declined by 75 percent. Other grassland birds have seen similar declines.

Dr. Mieke Titulaer leads the BRI’s research here.

“They keep declining,” Titulaer said. “These birds are grassland specialists, but they’re also among the easier birds to catch. We hope that by getting more information on these birds and what they need, we can develop management guidelines for these birds, but also other grassland specialists.”

The research is in its second year. It’s in partnership with the Dixon Water Foundation, which owns Mimms Ranch, and manages it for environmental and economic sustainability.

The research is a multi-national initiative, led by the Bird Conservancy of the Rockies. Canadian scientists study the birds in summer. There are three sites in Mexico, and there’s close collaboration across borders.

Captured sparrows are outfitted with tiny radio transmitters. Their batteries last six weeks, and in January, researchers were recapturing birds to replace old devices.

The transmitters allow researchers to track whether the birds survive, and what type of habitat they use, Titulaer said.

“We go once a day to see where they are,” she said. “We make a GPS point where the bird is. And at that point we sample vegetation – so we look at vegetation cover and height and the most important grass and forb species that are there, the percentage of bare ground.”

Preliminary results suggests that most sparrows settle into their own corner of the grasslands. The average home range is 18 acres. The birds also seem to prefer areas with dense grass cover, and little bare ground.

Trained specialists attach the transmitters, and operate the radio receivers. But the project relies on volunteers. And in terms of community engagement, it’s been a standout success for the BRI.

The Baird’s sparrow is the draw. It’s not easy to see the bird in Texas. Bill Sein of Alpine is an American Birding Association board member. He volunteered here last year, and described his Baird’s sightings on an online forum.

“All of a sudden I was getting contacted by birders all over the state,” Sein said, “to see if I could take them out and show them the Baird’s sparrow. I would say, ‘No, I can’t take you out there, but if you volunteer you can go out.’ We had probably 20 birders from all over the state last year.”

The decline of the birds is almost certainly tied to habitat loss. Eighty percent of the continent’s original grasslands are gone, transformed for agriculture. The Marfa grasslands – and others in Mexico – are isolated remnants. They allow grassland birds – and many other creatures – to cling to survival.

With new transmitters in place, sparrows are released – and vanish instantly into the golden expanse. But in the weeks to come, the data they generate will shed light on the grasslands – and what it takes to preserve its web of life.