In this study, we documented for the first time singing on the nest (SOTN) in 74% of 65 Northern Mockingbird (Mimus polyglottos) nests that were monitored with continuous-running video cameras (8,353.9 hrs sampled). As predicted, higher rates of SOTN significantly decreased daily survival rates of nests. SOTN occurred almost exclusively by females during the egg stage and in 86% (48/56) of nests for which we had sampling from the egg stage. While extensive at the population level, the average rate of SOTN per individual was very low (5.24 ± 1.24 s SOTN per hr video sampled). We found mixed support for the hypothesis that SOTN functions in territory maintenance. We found no support for the hypotheses that SOTN functions to coordinate parental care, defend nests, or aid in vocal learning. Given the limited attention SOTN has received and the mostly anecdotal accounts of it, our understanding of its costs and benefits is lacking. We conclude that while individual rates of SOTN are quite low, SOTN may be more widespread in populations than previously thought and that studies specifically designed to test hypotheses regarding potential functions are critically needed.

Data were collected from video cameras placed near mockingbird nests. A Python program screened the audio tracks from the videos for potential instances of singing on the nest (SOTN) and researchers verified whether singing occurred. Rate of singing on the nest was calculated by dividing the total SOTN duration in seconds by the total hours sampled for that nest. Likewise, rate of SOTN in different nest stages and at different times of day was calculated by dividing the amount of SOTN in sec in each interval by the total hours sampled during that interval.