Potoos (Nyctibius spp.) are nocturnal Neotropical canopy-dwelling birds, making them one of the most enigmatic and least known avian families. The Common Potoo (Nyctibius griseus) and the Great Potoo (Nyctibius grandis) are the most widespread species, but little information on their life histories is available. We evaluated the utility of autonomous recording units, coupled with automated signal recognition software, to monitor the calling behavior of both species for the first time over a complete annual cycle at six different sites in the Brazilian Pantanal. Their diel activity was restricted to the night, with higher calling rates after midnight. The breeding season of the Common Potoo, according to seasonal changes in vocal activity, seems to occur between July and November, while the breeding period of the Great Potoo extended from July to December. The reproduction periods proposed for each potoo in this study correspond mainly with the dry season in the study area and are in agreement with the few historical nest site observations from Brazil. The maximum calling activity of both species occurred between 1 and 5 a.m. September was the month with the maximum vocal activity of the Common Potoo, while the Great Potoo was most vocally during October. The vocal activity of neither potoo was related to night temperature. The Great Potoo was more vocally active during nights with high moon illumination. Our results will be useful in future monitoring programs for these species. Acoustic monitoring has proven to be a helpful tool for monitoring the presence and calling seasonality of the Common Potoo and the Great Potoo, mainly due to their naturally low vocal activity rates. Acoustic monitoring should be evaluated and used to increase our knowledge about the ethology and ecology of this enigmatic avian family.
