Biologists discover migratory patterns of two North American grassland bird species

February 5, 2019, Vermont Center for Ecostudies

Studying birds that nest in grasslands on the firing ranges and runways of active military installations is not for the faint of heart, but it proved to be a successful strategy for solving some vexing migration mysteries. Fundamental questions regarding the timing and choice of migration routes, and what that means for conservation of grassland bird populations have been surprisingly difficult to answer—until now. A new paper published in Ecology and Evolution sheds light on the annual movements of two grassland bird species and yields surprising results that may help transform the way we manage grassland bird populations, both across international borders and throughout their annual cycle.

Researchers from the Vermont Center for Ecostudies, with support from the U.S. Department of Defense Legacy Resource Management Program, have published the most extensive examination of the nonbreeding movement ecology for Grasshopper Sparrows (Ammodramus savannarum) and Eastern Meadowlarks (Sturnella magna) to date. By filling in fundamental knowledge gaps, this research will pave the way for cooperative endeavors to slow the decline of these grassland birds in the Midwest and Eastern United States.

"These results are a potential game changer for re-imagining conservation strategies for these grassland birds," explained Vermont Center for Ecostudies biologist Jason Hill. "Grassland bird management has been overwhelmingly focused on improving conditions on the breeding grounds. This is understandable especially for Grasshopper Sparrows, which are very hard to find outside of the breeding season when they're not singing. Our research reveals migration routes and specific wintering locations for several populations of Grasshopper Sparrows, and opens the door for a collaborative cross-border approach to managing them year-round."

Some migratory grassland birds spend nearly half their lives away from their breeding grounds, yet we know relatively little about this part of their annual cycle. To investigate the migratory patterns of these two species, the biologists deployed geolocators on 180 Grasshopper Sparrows and 29 Eastern Meadowlarks at Konza Prairie in Kansas, and at six U.S. Department of Defense installations across the species' breeding ranges. They were able to retrieve location data on 34 Grasshopper Sparrows and five Eastern Meadowlarks.

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To save these rare sparrows, researchers first must find, study them

When young Florida grasshopper sparrows leave home, they simply pop out of their nest, hidden on the ground, and walk off into the wild — still unable to fly.

Where the endangered birds go from there, and how many survive to produce their own young the following season, are mysteries that biologists urgently want to solve. If the youngest birds aren't faring well, then saving the species from extinction may require a risky, last-ditch measure: capturing most of the remaining sparrows in the hope they'll multiply in captivity.

"It's a bird that doesn't give up its secrets easily," said Erin Ragheb, a Florida Fish and Wildlife Conservation Commission scientist.

Of the few hundred surviving Florida grasshopper sparrows, nearly all are clinging to existence on state conservation land in Osceola County about 50 miles south of downtown Orlando.

Ecologists think they are the most endangered bird in North America. Central Florida was also home to the last bird to slip into extinction in the U.S.: the dusky seaside sparrow, which vanished in the late 1980s.

The effort by state and federal agencies and private conservation groups to bring Florida grasshopper sparrows back from the brink has recently accelerated. But it has also had to return to the essentials of the birds' existence: where they live, how many are born every year and what has caused them to plummet in numbers during the past decade. It's a race against time to learn enough about the bird to make a difference in its fate.

By comparison, troubled birds such as the California condor, bald eagle and scrub-jay are at least readily found and observed in the wild. But the grasshopper sparrow survives on its ability to remain elusive.

The few remaining birds live in vast prairies of knee-high grasses and shrubs, spending very little time above the vegetation, exposed. The bird's scientific name is Ammodramus savannarum floridanus; "ammodramus" is Latin for "sand runner."

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