Yellow rail auditory detection during the non‐breeding season

Yellow rails (Coturnicops noveboracensis) are secretive, nocturnal marsh birds that are challenging to survey. During the breeding season, males will respond to click‐click vocalization call playbacks and can also be detected using autonomous recording units (ARUs). Yellow rails will occasionally vocalize click‐click during spring migration but seldom, if ever, use this vocalization during autumn and winter. Consequently, detections of yellow rails have relied on effort‐intensive approaches such as draglines or serendipitous encounters. On 28 January 2022, we documented yellow rails vocalizing an unfamiliar call at a coastal marsh in Texas, USA. The vocalization was vaguely reminiscent of a sandhill crane (Antigone canadensis) call, and thus we called this vocalization a bugle. The bugle vocalization appears to be undocumented in the literature. To explore the frequency of vocalizations, we set out 4 ARUs at San Bernard National Wildlife Refuge, Texas from 30 January through 5 February 2022. We were also able to incorporate this vocalization into call‐playback surveys for multiple rail species at 5 sites along the Texas Gulf Coast from 14 February through 7 May 2022. Bugle vocalizations captured using ARUs appear to be most frequent from 1600–1800, and we tallied 327 of these vocalizations on ARUs during 1 week. Additionally, 31 individuals were detected during call‐playback surveys. The majority (21 of 31 individuals) came in response to playing the bugle vocalizations, while the remaining vocalizations were approximately evenly split between unsolicited vocalizing prior to the start of call playback, vocalizing in response to the click‐click call, and responding to other rail species playbacks. All vocalization responses during call playback were the bugle call. We suggest that future non‐breeding surveys for yellow rails use ARUs and call‐playback approaches that incorporate the bugle vocalization to document the presence of this species more efficiently. Yellow rails were recently recorded producing a previously undocumented vocalization in a coastal Texas salt marsh in January 2022. We found that this vocalization can be used to elicit the same vocalization in response during call‐playback surveys, and autonomous recording unit recordings demonstrate that yellow rails will also give this call unprompted. We suggest that this call may provide an alternative method for documenting the presence of yellow rails during the non‐breeding season.