U.S. Geological Survey

Southwestern willow flycatcher.

Scientists have created the first map of the entire range of the endangered southwestern willow flycatcher. It shows the bird’s habitat is threatened by drought and exotic beetles.

James Hatten of the U.S. Geological Survey used satellites to map vegetation near southwestern streams. That’s where the flycatcher breeds and builds nests.

“Basically what the Landsat satellites do is they can calculate how green and dense riparian vegetation is along creeks and rivers,” Hatten said. “I used that to create a habitat model of the flycatcher’s potential breeding sites throughout its range.”

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The data can be used to predict changes in flycatcher habitat. Hatten said drought has shifted the bird’s range eastward. Tamarisk beetles are another threat. The insects were introduced to control exotic tamarisk trees, which flycatchers nest in.

Hatten predicts the southern migration of the beetles will diminish flycatcher habitat by 36 percent on the Lower Colorado and by 55 percent on the Gila River. He found a 94 percent loss on the Virgin River in Nevada and Arizona, where beetles have defoliated trees for several years.  

Greg Beatty of the U.S. Fish and Wildlife Service is Arizona’s flycatcher expert.

“If you are a land manager and one of your goals is tracking and trying to manage riparian habitat, this model can try and give you a broad look at the changes in habitat,” he said.

Beatty said flycatcher populations have improved since the bird was listed as endangered two decades ago.

Source: J. Hatten - U.S. Geological Survey