King Rail ( Rallus elegans ) response to audio playback: implications for population estimation, monitoring methodology, and trapping approach

Abstract

Conspecific audio can be broadcast to improve detection probability (detectability) of secretive marsh bird species for population monitoring purposes and as a lure to more effectively trap individuals. Our primary objective was to describe King Rail (Rallus elegans) detectability as a function of distance and so determine if the distance sampling assumption of perfect detectability immediately adjacent to survey points was violated during call-broadcast surveys. We also described what factors affected King Rail detectability during audio broadcast surveys, and how and when this species was detected, and compared effectiveness of various King Rail call recordings used during trapping attempts. To accomplish these objectives, we experimentalized trapping efforts, radio-tagged 12 King Rails, and conducted repeated call-broadcast surveys for each radio-tagged individual in Michigan and Ohio, USA during the 2020 and 2021 breeding seasons. We found that King Rail detectability during 81 surveys was 0.39, which violates the aforementioned distance sampling assumption and necessitates a correction factor. Detectability within survey segments varied among survey periods, though overall detectability remained relatively constant, even after call-broadcast surveys in our study area typically end (post-survey period: 15 June to 10 July), which indicates that King Rail monitoring could effectively continue later than currently occurs. We found that grunt calls resulted in more captures than kek calls and that a multi-call track was most effective at trapping King Rails. Our findings could improve King Rail population estimates and increase success during trapping efforts, and may inform similar efforts for other secretive marsh birds.RESUMEN. La reproducción de grabaciones con-especificas pueden mejorar la probabilidad de detección (detectabilidad) de aves sigilosas de pantano con propósitos de monitoreo poblacional y como carnada para capturar individuos más eficientemente. Nuestro objetivo principal fue describir la detectabilidad de Rallus elegans como una función de la distancia para determinar si el supuesto de muestreo por distancia de detección perfecta de individuos inmediatamente adyacentes a los puntos de muestreo se violaba durante los monitoreos que utilizan reproducción de llamados. También describimos los factores que afectan la detectabilidad de Rallus elegans durante los monitoreos utilizando reproducción de audio, y como y cuando esta especie es detectada y comparamos la efectividad de varias grabaciones de llamados de Rallus elegans durante intentos de captura. Para cumplir con estos objetivos, experimentamos con el esfuerzo de muestreo, instalamos radios en 12 individuos de Rallus elegans y realizamos monitoreos repetidos utilizando reproducciones de llamados para cada uno de los individuos con radio en Michigan y Ohio, USA durante las temporadas de reproducción del 2020 y 2021. Encontramos que la detectabilidad de Rallus elegans durante 81 monitoreos fue de 0.39, lo cual viola el supuesto del muestreo por...

King Rail (Rallus elegans) presence in the Midwestern United States is predicted by local‐scale factors and avian community

“…In 2 years of call‐broadcast surveys at a northwestern Ohio wetland, no King Rails were detected, but trail cameras detected 13 individuals (Shirkey et al., 2017). In this same region, Brewer, Gehring, Shirkey, and Simpson (2023) found that radio‐tagged King Rails within 30 m of an observer were detected during <40% of call‐broadcast surveys. These results suggest that call‐broadcast surveys—a popular technique for monitoring secretive marsh birds—may often fail to detect King Rails in the Midwest, which poses a challenge for determining habitat associations of this species.…”