Despite Controversy, the Coastal California Gnatcatcher Will Remain an Endangered Subspecies

The fight to delist the bird hinged on disputed science—the same science behind an ongoing delisting petition for the Southwest Willow Flycatcher.

In late August, the U.S. Fish and Wildlife Service (USFWS) granted a reprieve to the coastal California Gnatcatcher, a tiny gray insectivore found in Southern California. Back in 2014, a group of builders associations with ties to the Pacific Legal Foundation submitted a petition to delist the bird, arguing that it isn’t a separate subspecies of California Gnatcatcher and therefore didn’t warrant protections under the Endangered Species Act. After more than a year of collecting evidence and listening to the recommendations of a panel of six independent experts who reviewed all the available scientific evidence, the USFWS declared that the coastal population is distinct enough from other California Gnatcatchers that it deserves to retain its protections under the Endangered Species Act.

The gnatcatcher wasn’t the only bird to face a delisting petition on account of its status as a subspecies, or even the only bird targeted by Pacific Legal Foundation and its partners. Still wending its way through the review process with the USFWS is a similar petition regarding the Southwest Willow Flycatcher. Both birds live in diminishing pockets of habitats: the gnatcatcher in coastal sage scrub, which has been highly fragmented by development, and the flycatcher in riparian corridors, 95 percent of which have disappeared due to land-use changes and drought. Life is particularly rough for the Southwestern Willow Flycatcher. This past year, Audubon scientists found only one of them on the 45,000-acre Kern River Preserve in California, an area that should be rich with the birds.

The basis of the reviews comes from two papers, published in 2013 and 2015, by Robert Zink, a conservation biologist at the University of Nebraska. Zink analyzed both the birds’ genomes and their ecological niches (basically, what kinds of habitats they use and how they use them) and concluded that the two subspecies were not different enough from the rest of California Gnatcatcherdom and Willow Flycatcherdom to warrant protections. His reasoning being that whatever genetic, ecological, or behavioral distinctness those populations have, losing them would not, in effect, be such a great loss.

Multiple scientists have taken issue with Zink’s conclusions. Tad Theimer of Northern Arizona University looked at how blunt an instrument the ecological niche modeling Zink used in his research can be. After running simulations, he wrote in 2016 that Zink’s methodology couldn’t differentiate between a flycatcher and a Yellow Warbler, let alone two flycatcher subspecies. In a 2014 paper, John McCormack of Occidental College examined both Zink’s niche modeling and his genetic analysis of the coastal California Gnatcatcher. He concluded that the data was insufficient to make a determination one way or another and flagged in particular Zink’s use of only a few select points on the gnatcatcher’s genome. McCormack argued that in order to make a definitive determination that the coastal California Gnatcatcher isn’t a subspecies, Zink should have looked at hundreds of spots on the bird’s genome. In both cases, scientists concluded that there simply wasn’t strong enough evidence to unequivocally declare that the disputed populations weren’t subspecies.

Zink is a well-regarded scientist. His peers have spoken highly of the quality of his past work, even when they completely disagree with the conclusions he drew regarding the flycatcher and gnatcatcher. If it stopped there, this would be a relatively standard scientific argument—the type of which has been going on in academic journals for decades. But in the background of this debate lurks the California Building Industry Association, one of the groups on both delisting petitions, represented by its lawyer Robert Thornton. It did not go unnoted that Zink thanks an R. Thornton for financial assistance on his 2013 gnatcatcher paper—the very paper used as the basis for the subsequent delisting petition. Multiple scientists interviewed for this story brought up the troubling implications; ample scientific research has shown that funding can subconsciously bias the conclusions of researchers even though they believe themselves impartial.

In the end, the six independent scientists working with the USFWS seemed to agree with the assessments of McCormack, with the USFWS noting, “Among the primary weaknesses of the research conducted by Zink et al. 2013 were the selection of genetic markers and lack of hypothesis testing. Specifically, the type of loci and analyses were not suited to identifying recent, intraspecific divergence.” With the Southwest Willow Flycatcher's fate still being determined, conservationists hope that the USFW will find the same faults with Zink's flycatcher research and deliver a similar rejection. But even when the final decision does get made, it will only take another bit of research to bring about another delisting petition. With so much potential money to be made, this isn't likely the last of these challenges we'll see.