In response to a petition (pdf) from the Pacific Legal Foundation (PLF) to delist the coastal California gnatcatcher (Polioptila californica californica) under the Endangered Species Act, the U.S. Fish and Wildlife Service made a 90-day finding (pdf) that the petition does not present substantial scientific or commercial information to indicate that delisting the species may be warranted.  PLF argued that the coastal California gnatcatcher is not a valid subspecies and should therefore be delisted.  In response, the Service acknowledged "that the taxonomic classification of the coastal California gnatcatcher has been the subject of considerable scientific debate."

The debate regarding the legitimacy of the coastal California gnatcatcher as a species has been ongoing since the time of listing of the species in 1993.  In part, the debate stems from disagreement about the role of morphology (physical appearance such as feather color or tail length) versus genetics in distinguishing among species and subspecies.

Despite the fact that it acknowledged scientific debate regarding the taxonomic classification of the gnatcatcher, the Service concluded that "[t]he genetic information provided in the petition and assertions of improper statistical analyses have been the focus of several Service and independent scientific reviews and the Service has concluded that the information is insufficient to support reclassification."  (Citations omitted from quotation.)