The moon phase affects the ecology and vocal activity of nightjars (Caprimulgidae). However, some studies have found contradictory results regarding the impact of the moon phase on the vocal activity of nightjars. To increase our knowledge on this topic, we monitored the vocal behavior of two Neotropical nigthjars, the Little nightjar (Setopagis parvula) and the Common pauraque (Nyctidromus albicollis), over 5 lunar cycles in the Brazilian Pantanal. We tested the relationships between the moon phase and daily vocal output (number of calls uttered) and the proportions of calling activity at dusk, midnight, and dawn. Our results suggest that moonlight stimulated the vocal output of both species, since it was between 6 and 8 times higher during full moon nights than during new moon nights. Likewise, the proportion of calling activity at midnight was significantly higher during full moon nights. In contrast, the proportion of calling activity of both species was higher at dawn during new moon nights than under the full moon. The calling activity of the Common pauraque was also higher at dusk during new moon nights. These findings might be partly related to the much lower vocal output at midnight during full moon nights and therefore higher proportions of vocal activity at dusk and at dawn under new moon scenarios. This is the first study comparing the vocal behavior of two Neotropical nightjars over different moon phases and shows that the impact of moonlight may differ between species and at a daily scale when analyzing the periods with the highest and lowest illumination. The consequences of the increase in vocal output under moonlight are unknown and should be assessed.

月相会影响夜莺（Caprimulgidae）的生态和发声活动。然而，一些研究发现了关于月相对夜鹰发声活动影响的矛盾结果。为了增加我们对这个主题的了解，我们监测了两个新热带黑夜莺的发声行为，小夜莺 ( Setopagis parvula ) 和普通 pauraque ( Nyctidromus albicollis))，在巴西潘塔纳尔湿地超过 5 个月球周期。我们测试了月相和每日声音输出（发出的呼叫次数）以及黄昏、午夜和黎明时呼叫活动的比例之间的关系。我们的结果表明，月光刺激了这两个物种的声音输出，因为它在满月之夜比新月之夜高 6 到 8 倍。同样，在满月之夜，午夜通话活动的比例明显更高。相比之下，这两种物种在新月之夜的黎明时的呼叫活动比例高于满月时。在新月之夜的黄昏，普通 pauraque 的呼叫活动也更高。这些发现可能部分与满月夜午夜的声音输出低得多，因此在新月情景下黄昏和黎明的声音活动比例更高。这是第一项比较两个新热带夜鹰在不同月相上的发声行为的研究，并表明在分析最高和最低照度的时期时，月光的影响可能因物种而异，并且在日常尺度上有所不同。月光下声音输出增加的后果尚不清楚，应进行评估。这是第一项比较两个新热带夜鹰在不同月相上的发声行为的研究，并表明在分析最高和最低照度的时期时，月光的影响可能因物种而异，并且在日常尺度上有所不同。月光下声音输出增加的后果尚不清楚，应进行评估。这是第一项比较两个新热带夜鹰在不同月相上的发声行为的研究，并表明在分析最高和最低照度的时期时，月光的影响可能因物种而异，并且在日常尺度上有所不同。月光下声音输出增加的后果尚不清楚，应进行评估。