Wildlife Diversity Program Quarterly Report for January–March 2025
Detecting the Elusive Black Rail Using Remote Technologies
by Kacy Cook, Coastal Waterbird Biologist and Brooke Calisto, Waterbird Technician
O ver the winter and early spring, the marshbird team has been organizing and analyzing data collected using Autonomous Record- ing Units (ARUs), wildlife cameras, and water level monitors during pilot 2024 Black Rail surveys. Thirteen ARUs and 11 water level monitoring stations were deployed on game lands in the Cedar Island region for up to 73 days between April 4 and July 31, 2024. One ARU was also deployed at Fort Fisher State Park from April 29 to May 8, 2024, but resulted in no detections of Black Rails. In the Cedar Island region, collection of consistent ARU data was made more challenging by black bear disturbance, equipment failures, and staffing issues. However, ARUs detected Black Rail ‘ink’ calls on both game lands, suggesting that Black Rails were actively nesting at these sites. In total, the deployed ARUs recorded at least 15,000 Black Rail calls, most of which were the more commonly heard ‘ki-ki-do’ call. Of five ARUs deployed in a single marsh on a gradient from marsh edge to marsh interior along the forest edge, the number of Black Rail detections was highest in the herbaceous high marsh along the marsh interior, an area dominated by saw grass and with few trees or shrubs. There were no Black Rail detections in marsh areas closest to the water’s edge and dominated by black needlerush and sparse high marsh vegetation. The other 8 ARUs were deployed along the forest edge and interior of a different area of marsh. This marsh had a higher number of detections than the marsh described above when controlling for number of ARUs and recording time. Of a total of 73 recording days, Black Rail calls were detected on only 10 days on average by any single ARU, supporting findings by other researchers that Black Rail calling activity is sporadic and detection probability from passive listening surveys is low. Deployment of ARUs, therefore, greatly increases the likelihood of detection and provides higher quality survey data for documenting Black Rail occupancy. Water level data collected between April 4 and August 20, 2024, suggest that there was a flooding event around May 20 during which up to 9.5 inches of water flooded the high marsh and could potentially have drowned eggs and chicks. It appears that there was not another flooding event until August 13, after the chick rearing period would have likely been completed. Eight camera traps were also deployed on game lands in the Cedar Island area from September 19, 2024, through March 6, 2025, in an attempt to detect Black Rail adult flightless molt and winter activity. No Black Rails were detected during this period.
NCWRC
Wildlife Technician, Brooke Calisto, after hav- ing completed maintenance of a deployed water level monitoring station and autono- mous recording unit (ARU).
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