willow flycatchers, already an endangered species, also imperiled by climate change

The southwestern willow flycatcher is facing serious environmental challenges.



Of the four subspecies of willow flycatcher, three have breeding grounds in California and are listed as endangered by the state’s Department of Fish and Wildlife. Because the southwestern subspecies, one of those three subspecies, is listed as endangered by the federal Fish and Wildlife Service, ecologists and conservation biologists have studied the birds closely for decades. Scientists have tried to gather information using traditional research methods such as attaching unique identification bands to the birds’ legs, but that provides only limited data because too few of the birds are recaptured for further study.




“Rare populations are the most threatened by climate change, and the southwestern subspecies that’s already endangered is the most vulnerable, based on our analysis,” said Kristen Ruegg, a UCLA assistant adjunct professor and the paper’s co-lead author with Rachael Bay, a UCLA postdoctoral fellow. 


The flycatcher relies heavily on “riparian” habitats — lush areas along rivers and other bodies of water. Unfortunately, those places are prime targets for development, so some of those habitats could disappear.

“When they dry up and go away, there goes the habitat for the southwestern willow flycatcher,” Ruegg said.


“In general, the population of willow flycatchers in California has been on the decline for quite a while,” Whitfield said. “It used to be pretty widespread in the Central Valley, and now you rarely see it at all except when it’s migrating through.”





“This subspecies of flycatcher is sort of the canary in the coal mine,” he said. “If we can detect impacts on this species, chances are that climate change is also going to be affecting other species as well.”