First confirmed hybrid pairing between a Cerulean Warbler and a Black-throated Blue Warbler (Setophaga caerulescens)/Primer hibrido conflrmado de una pareja entre los chipes Setophaga cerulea y S. caerulescens

Hybridization events have long interested biologists because of their implications for species concepts and taxonomy. Documenting hybridization events is important because hybridization rates are commonly used as support for accepted taxonomic divisions. In July 2017, we observed a nest where a male Cerulean Warbler (Setophaga cerulea) and a female Black-throated Blue Warbler (Setophaga caerulescens) were feeding nestlings. The Cerulean Warbler and Black-throated Blue Warbler communicated with each other using song (male) and calls (female), similar to a non-hybrid pair of either parent species, and the pair was not observed to engage in aggressive behaviors toward each other. Interestingly, the Black-throated Blue Warbler is not known to breed in Indiana, although it is a regular migrant in the spring and fall. We describe the behaviors of the hybrid pair at the nest, provide photographs and audio recordings for documentation, and hypothesize that this instance of hybrid pairing may have occurred due to mate scarcity. Received 1 November 2017. Accepted 8 August 2018. Key words: Black-throated Blue Warbler, Cerulean Warbler, hybrid, Parulidae, Setophaga caerulescens, Setophaga cerulea. wood-warbler. (Spanish)--Los eventos de hibridacion han interesado a los biologos por mucho tiempo debido a sus implicacioncs con los conceptos de especie y la taxonomia. La documentacion de estos eventos es importante porque las tasas de hibridacion son comunmente usadas en apoyo de divisiones taxonomicas aceptadas. En julio de 2017. observamos un nido en el que un macho del chipe Setophaga cerulea y una hembra de S. caerulescens alimentaban polluelos. Ambos chipes se comunicaban entre si utilizando su canto (macho) y llamado (hembra), de modo similar a una pareja no-hibrida de cualquiera de las especies parentales. y la pareja no fuc observada teniendo comportamientos agresivos hacia el otro. Es interesante senalar que no se sabe que S. caerulescens anide en Indiana, aunque es una migratoria regular en primavera y otoiio. Describimos los comportamientos de la pareja hibrida en el nido, proporcionamos fotografias y grabaciones de audio como documentacion e hipotctizamos que csta instancia de una pareja que se hibridizo pudiese haber ocurrido por la escasez de parcjas. Palabras clave: Chipes, hibrido, Parulidae, Setophaga caerulescens, Setophaga cerulea.