iButton® Temperature Loggers Effectively Determine Prairie Grouse Nest Absences

Recent technological innovations allow the monitoring of avian nest attendance in ways that reduce disturbance and expense without altering nesting activities. Yet the efficacy of these techniques to assess nest absences has not been determined for ground-nesting prairie grouse. We sought to determine the timing of nest absences by means of accurate detection without intrusive human visitations technology. During the nesting season (May and June), we inserted iButton® Thermochrons (Maxim/Dallas Semiconductor Corp., Sunnyvale, CA) into active greater prairie-chicken (Tympanuchus cupido) nests in the Sandhills of Nebraska, USA. We simultaneously monitored the nests with solar-powered video cameras to determine if the lower-cost iButtons would record noticeable changes in nest bowl temperature when video indicated a hen absence. Our data showed that iButtons detected 88% of nest absences in 49 off-bouts (instances of nest absence) and accurately portrayed the length of absence from the nest. In total, average lag time, departure lag time, and arrival lag times were detected by iButtons less than 2 minutes after the actual time recorded by the camera. We also obtained valuable information regarding the timing of hen absence, predation events, and optimal iButton recording intervals. Our study suggests that iButtons could be effectively used to monitor absences at greater prairie-chicken and likely other species of prairie grouse nests in future studies.