Vocal repertoire of cooperatively breeding Smooth-billed Anis

Calls are functionally diverse signals that mediate behavior in a wide variety of contexts in both passerines and non-passerines. However, the call-based acoustic communication systems of non-passerines have received less attention from investigators than those of passerines. We examined the vocal repertoire of Smooth-billed Anis (Crotophaga ani), cooperatively breeding cuckoos that live in groups with multiple breeding pairs. We recorded calls from 22 groups over two breeding seasons at the Cabo Rojo National Wildlife Refuge in Puerto Rico. We identified 11 call types and one group vocalization, and used an automated sound measurement program to quantify their acoustic features. Discriminant function analysis (DFA) correctly classified 74.2% of calls based on these features. The vocal repertoire of Smooth-billed Anis is larger than that reported for the three other species in the subfamily Crotophaginae. Smooth-billed Anis have at least two alarm calls, two nest-specific calls, and one nest defense call. We also identified one possible signal of aggressive intent, one possible appeasement signal, and two calls that may communicate identity. The relatively large vocal repertoire of Smooth-billed Anis and association of distinct call types with different functions and contexts supports the main prediction of the social complexity hypothesis, i.e., species with more complex social systems will have more complex communication systems. Repertorio vocal de Crotophaga ani ave que exhibe reproducción cooperativa Las llamadas son señales funcionalmente diversas que median la conducta en una amplia variedad de contextos, tanto en paseriformes como en aves no-canoras. Sin embargo, los sistemas de comunicación acústica de los no-paserinos ha recibido menos atención, de parte de los investigadores, que los paseriformes. Examinamos el repertorio vocal del Garrapatero (Crotophaga ani), que vive en grupos con múltiples parejas y llevan a cabo reproducción cooperativa. Grabamos las llamadas de 22 grupos durante dos épocas reproductivas en el Refugio Nacional de Vida Silvestre de Cabo Rojo, Puerto Rico. Utilizamos un programa automatizado para medir y cuantificar los parámetros acústicos que permitió identificar 11 llamadas y una vocalización de grupo. Se usó un análisis de función discriminativa (DFA) para clasificar correctamente el 74.2% de las llamadas con sus respectivas particularidades. El repertorio vocal del Garrapatero es mayor que el informado para otras tres especies en la subfamilia Crotophaginae. Los garrapateros tienen al menos dos llamadas de alarma, dos llamadas especificas en el nido, y una llamada de defensa al nido. Además identificamos una posible señal de intento de agresión, otra posible señal de apaciguamiento y dos llamadas que pudiera comunicar la identidad de un individuo. El gran repertorio vocal del Garrapatero y la asociación a distintos tipos de llamadas con diferentes funciones y contextos, apoya la predicción de la hipótesis de complejidad social, ej. que las especies con sistemas sociales más complejos tendrán los sistemas de comunicación más complejos. Disclaimer: Supplementary materials have been peer-reviewed but not copyedited. Audio S1. Four ahnee calls. Audio S2. Three ahnee alarm calls. Audio S3. Three chlurp calls. Audio S4. Three chlurr calls. Audio S5. Four chuck calls. Audio S6. Two ee-oo-ee calls. Audio S7. Two growl calls. Audio S8. Four hoot calls. Audio S9. Four warble calls. Audio S10. Three whine calls. Audio S11. Two whistle calls. Audio S12. Ahnee chorus featuring introductory ahnee calling by a single bird, followed by whine, ahnee, and chuck calls made by additional group members. Audio S13. Ahnee chorus featuring ahnee calls by multiple birds and some faint chuck calls. Audio S14. Ahnee chorus featuring ahnees, whines, chucks, and hoot calls. Table S1. Mean (± SD) minimum and maximum values of acoustic variables for 11 Smooth-billed Ani calls types. Numbers in brackets after each call type represent the number of groups sampled. One high quality (high signal-to-noise-ratio) example of each available call was chosen from each group for analysis. Table S2. Mean (± SD) variance of the acoustic variables measured for the 11 Smooth-billed Ani calls types analyzed. Numbers in brackets after each call type represent the number of groups sampled. One high quality (high signal-to-noise-ratio) example of each available call was chosen from each group for analysis. Table S3. Standardized canonical discriminant function coefficients of the seven acoustic parameters chosen by the stepwise model selection procedure used for discriminant function analysis of eight Smooth-billed Ani calls. Table S4. Cross-validation results from discriminant function analysis (DFA). Numbers in bold indicate the number of calls assigned to each category, while numbers in brackets represent the percentage of calls assigned to each category. The sample size of each call is in brackets in the call type column. Overall, the DFA correctly classified 74.2% of calls using cross validation. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

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