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Although heterospecific vocal imitation is well documented in passerines, the evolutionary correlates of this phenomenon are poorly known. Here, we studied interspecific variation in vocal mimicry in a comparative study of 241 European songbirds. We tested whether vocal mimicry is a mode of repertoire acquisition or whether it resulted from imperfect song learning. We also investigated the effect of the degree of contact with the vocal environment (with species having larger ranges, abundance, or being long lived having a higher degree of mimicry) and a possible link with cognitive capacity (an overall larger brain in species with mimicry). Finally, we determined the potential evolutionary role of vocal mimicry in different interspecific contexts, predicting that mimicry may affect the intensity of brood parasitism, predation, or degree of hybridization. While controlling for research effort and phylogenetic relationships among taxa, we found that effect sizes for intersong interval, brain size, breeding dispersal, abundance, age-dependent expression of repertoires, and predation risk reached a level that may indicate evolutionary importance. Vocal mimicry seems to be a consequence of song continuity rather than song complexity, may partially have some cognitive component but may also be dependent on the vocal environment, and may attract the attention of predators. However, estimates of sexual selection and interspecific contacts due to brood parasitism and hybridization varied independently of vocal mimicry. Therefore, mimicry may have no function in female choice for complex songs and may be weakly selected via interspecific associations. These findings provide little evidence for vocal mimicry having evolved to serve important functions in most birds.

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While male song and its functions have been well studied, female song has often been overlooked. In this study, we provide a detailed description of the spontaneous female song in a well-studied northern temperate songbird, the European Starling (Sturnus vulgaris). We compared the song organization, complexity, and composition of female and male starlings housed in large outdoor aviaries. Overall, the general organization was similar in both sexes, and some females sang complex song bouts of more than 30 seconds of uninterrupted song. Although some females were capable of singing the four phrase-type categories typically found in male song bouts (whistle, variable, rattle, and high-frequency phrase types), a significantly lower proportion of females sang all four categories of phrase type as compared to males. Our results also revealed large individual variation in song characteristics among females: repertoire size varied between 11 and 36 phrase types, while average song bout length ranged between 10 and 26 seconds. All song parameters (total repertoire size, song bout length, and repertoire size within the four different phrase categories) were significantly lower in females than in males. Nevertheless, except for the number of rattle phrase types, song parameters overlapped between the sexes demonstrating that some females produced a more complex song than some males. Canto de la Hembra en Sturnus vulgaris: Diferencias entre Sexos, Complejidad y Composición Resumen. Mientras que el canto del macho y sus funciones han sido bien estudiados, el canto de las hembras ha sido menos estudiado. En este estudio, brindamos una descripción detallada del canto espontáneo de la hembra en una especie bien estudiada de ave canora del norte templado, Sturnus vulgaris. Comparamos la organización del canto, la complejidad y la composición entre machos y hembras en aviarios de gran tamaño emplazados al aire libre. En total, la organización general fue similar en ambos sexos, y algunas hembras cantaron unidades de canto complejas durante más de 30 segundos de modo ininterrumpido. Aunque algunas hembras fueron capaces de cantar las cuatro categorías de tipos de frases típicamente halladas en las unidades de canto de los machos (silbido, variable, matraqueo y tipos de frases de alta frecuencia), una porción significativamente menor de las hembras cantó todas las cuatro categorías de tipos de frases en comparación con los machos. Nuestros resultados también revelaron gran variación individual entre hembras en las características del canto: el tamaño del repertorio varió entre 11 y 36 tipos de frases, mientras que la duración promedio de la unidad de canto fluctuó entre 10 y 26 segundos. Todos los parámetros examinados del canto (tamaño total del repertorio, duración de la unidad de canto y tamaño del repertorio dentro de las cuatro categorías diferentes de frases) fueron significativamente menores en las hembras que en los machos. A pesar de ello, a excepción del número del tipo de frases de matraqueo, los pará metros del canto se superpusieron entre los sexos, implicando que algunas hembras produjeron un canto más complejo que algunos machos.