On November 6th, 2015, Ian Davies and others birding Sabal Palm Sanctuary (Cameron County) as part of the Rio Grande Valley Birding Festival identified a yellowish Empidonax flycatcher as a Yellow-bellied Flycatcher. The following day (November 7th), Doug Gochfeld was able to make an audio-recording of this bird as it seemed to match up to vocalizations of Pacific-slope Flycatcher. Doug's recording can be found here. Byron Stone was also able to record it the following day, with that recording here.
This bird remained quite faithful to the location where it was discovered, and was seen by many until at least April 7th, 2016.
The TBRC carefully considered this record and unanimously (9-0) voted to accept it as the first documented state record. The audio recordings served as the key artifacts in the documentation of this record.
As many certainly know, Pacific-slope Flycatcher and Cordilleran Flycatcher were once considered the same species - Western Flycatcher - until studies of the complex led to the species being split into 2 recognized species in 1989. This split has been considered problematic since that time, and more recent studies have shown that intergrades between the two exist in areas where their breeding ranges come in close contact. Additionally, there is no diagnostic way to reliably identify species visually in the field nor in the hand as there are overlapping field marks.
Identification of either species by vocalization(s) is also rather difficult, especially by ear without a good recording. There is some overlap of vocals between Cordilleran and Pacific-slope and some birds seem to make sounds that are intermediate between the two. The one vocalization that can be used to make an identification is a bird's position note call. With a high quality recording, the difference between the 2 species' calls should readily show up on a spectrogram. Both recordings submitted with this first state record showed the "classic" signature of a Pacific-slope Flycatcher.
The TBRC acknowledges that this split is considered problematic by many but feels that this Sabal Palm bird is a good match for the birds that the AOU currently recognizes as a full species - Pacific-slope Flycatcher. We are also aware that this record is probably not the first time that Pacific-slope Flycatcher has been found in Texas. Other candidate birds, including a couple in low-elevation areas in the fall & winter seasons, have been studied in Texas but none previously have had solid audio-recordings of the bird's position note included in any documentation submitted to the TBRC. The TBRC encourages observers who see out-of-range "Western" Flycatcher to make efforts to obtain audio-recordings when possible to establish a pattern of vagrancy for this species in Texas.
Secretary, Texas Bird Records Committee, February 2017.