Singing on the nest is a widespread behavior in incubating Northern Mockingbirds and increases probability of nest predation

ABSTRACT 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 hr 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 of 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 low (5.24 ± 1.24 s SOTN per hour of 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. LAY SUMMARY In some bird species, individuals will sing while sitting on the nest (SOTN); however, little is known about this behavior. Why do birds that hide their nests engage in this conspicuous behavior that could draw the attention of nest predators? We used video recordings from 65 Northern Mockingbird nests to provide the first evidence that mockingbirds sing on the nest. Singing on the nest occurred in 86% of nests with sampling during the egg stage, but rates of singing on each nest were low. Almost all singing events were by females incubating eggs. As predicted, higher rates of singing led to increased rates of nest predation. We found mixed evidence that singing functions in territory maintenance and no evidence that singing functions in coordination of parental care, nest defense, or vocal learning. We conclude that rare SOTN may be more widespread than previously thought and needs further study to understand its function. RESUMEN En este estudio, documentamos por primera vez el canto en el nido en el 74% de los 65 nidos de ruiseñor común (Mimus polyglottos) que fueron monitorizados con cámaras de vídeo de funcionamiento continuo (8.353,9 horas muestreadas). Como se predijo, las mayores tasas de SOTN disminuyeron significativamente las tasas de supervivencia diaria de los nidos. El SOTN se produjo casi exclusivamente por parte de las hembras durante la fase de huevo y en el 86% (48/56) de los nidos de los que se tomaron muestras desde la fase de huevo. Aunque extensa en el nivel de población, la tasa media del cantas en el nido por individual fue muy baja (5,24 ± 1,24 s SOTN por hora de vídeo muestreada). Encontramos un apoyo mixto a la hipótesis de que la cantas en el nido funciona en la defensa del territorio. No encontramos apoyo para la hipótesis de que la canto en el nido funciona para coordinar el cuidado parental, defender los nidos o ayudar en el aprendizaje del canto. Dada la escasa atención que ha recibido la SOTN y los relatos mayoritariamente anecdóticos sobre ella, carecemos de conocimientos sobre sus costes y beneficios. Llegamos a la conclusión de que, mientras tasas de la canto en el nido de individuales son bajos, la canto en el nido en las poblaciónes puede estar más extendida de lo que se pensaba y que se necesitan urgentemente estudios diseñados específicamente para poner a prueba las hipótesis sobre sus posibles funciones.