When a group of researchers at Texas A&M鈥檚 Natural Resources Institute published the first that surveyed the presence of a brightly colored Texas songbird across a huge swath of Texas, the results were astounding: The population of the endangered golden-cheeked warbler in the state was estimated to be 10 times larger than previously thought.
The 2012 study did not advocate changing the species鈥� endangered status, nor did it imply that conservation measures to protect its habitat were no longer necessary, researchers .
鈥淩ather,鈥� said Heather Mathewson, the lead researcher, 鈥渢his study is one of many necessary steps in our evolving knowledge of the golden-cheeked warbler.鈥�
鈥淸It] is not intended as the final word on the matter,鈥� she added.
Nonetheless, the data point 鈥� without indicating whether the warbler鈥檚 population was increasing or decreasing in Texas 鈥� has fueled an almost decade-long legal battle over the bird with a bright yellow face and striking black marks. In 2015, the Texas Public Policy Foundation and Susan Combs, a Republican state leader who had served as Texas鈥� Comptroller, Commissioner of Agriculture and as a state representative, petitioned the federal government to remove the warbler from the endangered species list. The petition used Mathewson鈥檚 study as primary evidence that the bird no longer needed such stringent federal protections.
鈥淭he time has come to remove the golden-cheeked warbler from the endangered species list,鈥� the petitioners argued. 鈥淒elisting this species is now compelled by today鈥檚 best available science.鈥�
The latest lawsuit to remove the bird from the endangered species list , part of a heated legal battle for which the 2012 study and its fundamental research question 鈥� how many golden-cheeked warblers exist in Texas? 鈥� has become a lightning rod. The ongoing fight comes as Central Texas faces as the state鈥檚 .
The federal government, in rejecting attempts to delist the bird, attacked the research methods of the biologists. Meanwhile, the TPPF 鈥� and eventually, the Texas General Land Office 鈥� characterized the study鈥檚 findings beyond what they actually suggested, arguing that the bird鈥檚 population had recovered and did not face any current significant threats.
鈥淭his really shouldn鈥檛 be controversial,鈥� said Michael Morrison, a professor of wildlife and fisheries sciences at Texas A&M and one of the wildlife biologists who worked on the 2012 study. 鈥淵ou would think we should be celebrating the fact that 鈥� the bird is far better off than we thought.鈥�
The federal government the population of male warblers at about 27,000, based on a 2007 estimate by SWCA Environmental Consultants for the Texas Department of Transportation. Mathewson and her colleagues estimated the actual number is closer to 263,000. In a five-year review of the bird鈥檚 status published in 2014, the Fish and Wildlife Service wrote that the differing estimates underscored the need for more information.
A separate assessment of the bird鈥檚 population conducted in 2018 by Jim Mueller, a U.S. Fish and Wildlife Service scientist, estimated that there may be about 233,000 male warblers in Texas; those results are still undergoing peer-review for publication in a journal, he wrote in an email to the Tribune.
鈥淭he current population size is much larger than was estimated,鈥� Mueller said in a comment. 鈥淭hat is fantastic news.鈥�
鈥淥n the flip side, threats to the species continue, such as loss of habitat,鈥� he said.
Human habitat encroaching on warbler country
The golden-cheeked warbler鈥檚 habitat ranges across a 35-county region of Central Texas from west of San Antonio up to the Dallas-Fort Worth metropolitan area. It follows and expands northwest of the Interstate 35 corridor, a rapidly growing region of Texas where the population of humans between 1990 and 2010. The bird was first listed as endangered in 1990; the primary considerations were the rapid decline of habitat and its small estimated population size.
The migratory songbird breeds in Texas between late February and the end of April before heading south to Central America in the late summer. Its breeding range extends across 67,000 square kilometers, or roughly 25,900 square miles, of Texas, Mueller said. But, only about 4% of that area is suitable woodland habitat since the bird relies on Ashe juniper bark to nest, he added.
The federal government has previously rejected Texas鈥� attempts to delist the bird based on new population estimates alone. The U.S. Fish and Wildlife Service argues that there isn鈥檛 evidence to suggest threats to the bird鈥檚 existence have been reduced. In fact, the opposite has been found: Destruction of the bird鈥檚 habitat has only accelerated across Central Texas as suburbs expand around San Antonio, Austin and Dallas. that between 2001 and 2011, the golden-cheeked warbler鈥檚 habitat shrunk by 29%. Scientists have found that the primary drivers of its habitat loss are rapid suburban development outside of Austin and San Antonio.
The Texas General Land Office manages state-owned lands and mineral rights totaling 13 million acres, . After the federal government rejected its first attempt to delist the bird, the Texas General Land Office joined a 2017 lawsuit to delist the bird by the TPPF, arguing that the agency leases lands to benefit the Permanent School Fund, and endangered species restrictions lowered property values.
On appeal, a the Fish and Wildlife Service to reconsider Texas鈥� petition, stating that the federal agency had used an incorrect legal standard to evaluate whether the bird鈥檚 endangered status should be reconsidered. The federal agency issued another finding in July, again rejecting the attempt to begin a process that could delist the bird.
鈥淭hese efforts represent new estimates rather than indicators of positive trends in warbler habitat and population size, and thus do not imply recovery,鈥� the Fish and Wildlife Service wrote of the 2012 population study.
But Ted Hadzi-Antich, a senior attorney with the Texas Public Policy Foundation and lead counsel on the warbler case, argues to the contrary.
鈥淭o my mind, it鈥檚 pretty clear that [the population] is increasing, and that the habitat fragmentation, predation and urbanization have not been adversely impacting the warblers,鈥� he said.
Hadzi-Antich said that the state鈥檚 General Land Office is likely the single most impacted entity by the continued listing of the golden-cheeked warbler. For example, he said about 85% of a 2,300-acre parcel of land between Bexar and Kendall counties is considered warbler habitat; GLO estimated that the endangered species protections on that specific site have decreased its property value by 35%.
鈥淭hey wanted to develop that property, but with this diminution in value, that became problematic,鈥� he said. 鈥淣obody wants to see species become extinct. The problem is, you鈥檝e got palpable adverse impacts on humans from some of these requirements.鈥�
鈥淭he [Endangered Species Act] is intended to protect species from extinction, not protect species from the supposition that there may be a threat,鈥� he added.
, the Texas land commissioner and a candidate for Texas attorney general, has long fought against Endangered Species Act protections that block urban development. In 2015, challenging how species are listed. On Wednesday, the U.S. Fish and Wildlife Service again, arguing that the federal government refused to abide by the judge鈥檚 instructions.
In a statement, a spokesperson for the Fish and Wildlife Service said the agency does not comment on pending litigation.
Conservation advocates, meanwhile, generally agree with the federal government that the threats still exist to the warbler鈥檚 population.
鈥淪cientists from around the world are ringing the alarm bells that we鈥檙e in an ,鈥� said Noah Greenwald, the endangered species director at the Center for Biological Diversity, a nonprofit advocacy group. 鈥淭he golden-cheeked warbler challenges us to protect woodlands in an area that鈥檚 being rapidly developed.鈥�
, a Democrat state representative who has advocated for conservation of natural areas and represents , west of Austin 鈥� which includes a large swath that serves as habitat for the golden-cheeked warbler 鈥� said the increased costs to developers from the endangered species protections don鈥檛 entirely block growth, and the current rules help to protect natural areas in the Texas Hill Country.
鈥淲arbler habitat is largely in some of the most desirable places to build in the state,鈥� Zwiener said. 鈥淲e are still experiencing rapid growth despite the protections.鈥�
鈥淗onestly, I don鈥檛 know many people around here who would complain about development being slightly slower,鈥� she added.
Science caught in the middle
Evolving science 鈥� better surveys, better models, more testing 鈥� provided the ammunition for the hotly contested legal battle over the development of Central Texas. Morrison, the biologist who worked on the 2012 study, said he鈥檚 frustrated by the way researchers and the science supporting their findings have been characterized along the way.
鈥淲e鈥檝e been accused by environmentalists that somehow, we as the scientists want [the warbler] to not be [on the] endangered [list],鈥� Morrison said.
The Fish and Wildlife Service sought in part to discredit Morrison and his colleagues, arguing that the estimate of land occupied by the birds used in the study was not reliable and that it may have led to an inflated estimate of the total population. But Roel Lopez, director of Texas A&M鈥檚 Natural Resources Institute, said that researchers used robust methodology, the most current technology available and random sampling to determine potential habitat and the population estimate.
鈥淭he methods back then [in 1990, when the warbler was first listed as endangered] may not have been as robust, or there wasn鈥檛 a lot of information,鈥� Lopez said. 鈥淭hrough time, there may be an increased effort to survey and sample more, so it鈥檚 not uncommon for us to work on a species and 鈥� through an increase in effort 鈥� actually find more of them.鈥�
On the other hand, the assertion by the TPPF that the bird鈥檚 population has ballooned since 1990 is very unlikely and not supported by research, experts said. Scientists may never know how many birds there were in 1990 or how much the population has declined since then.
But, Morrison said that misses the larger problem, which is how to ensure enough warbler habitat remains in Texas Hill Country.
鈥淲e need to be focusing on working with landowners to maintain large continuous tracts of habitat, give them tax breaks, and reasons to maintain that,鈥� Morrison said. 鈥淔ighting over whether or not there鈥檚 100,000 or 200,000 [male birds], to me, is kind of not the point.鈥�
Disclosure: The Texas General Land Office and the Texas Public Policy Foundation have been financial supporters of The Texas Tribune, a nonprofit, nonpartisan news organization that is funded in part by donations from members, foundations and corporate sponsors. Financial supporters play no role in the Tribune's journalism. Find a complete .
