J. Field Ornithol. 77(3):291–301, 2006 DOI: 10.1111/j.1557-9263.2006.00055.x Song ranging by incubating male Blue-headed Vireos: the importance of song representation in repertoires and implications for song delivery patterns and local/foreign dialect discrimination Eugene Sillar Morton, 1,5 Joan Howlett, 2 Nicole Christine Kopysh, 3 and Ioana Chiver 4 1 Migratory Bird Center, Smithsonian Institution, National Zoological Park, Washington, DC 20008, USA 2 3662 Kinter Hill Road, Edinboro, PA, 16412 USA 3 Ontario Breeding Bird Atlas, c/o University of Guelph, Blackwood Hall, Guelph, Ontario N1G 2W1, Canada 4 Department of Biology, York University, Toronto, Ontario M3J 1P3, Canada Received 17 November 2005; accepted 28 February 2006 ABSTRACT. Mechanisms used by birds to range their distance from singing conspecifics are being debated. In particular, the idea that an incoming song must be in a bird’s repertoire for it to be ranged accurately is controversial, but important to our appreciation of the role ranging plays in song evolution. We tested the relation between ranging accuracy and songs in repertoires in playback experiments to male Blue-headed Vireos (Vireo solitarius ) whose precise locations were known because they were incubating eggs. Males ranged songs heard while incubating and, when their mates relieved them at the nest, flew directly to the silent playback sites, suggesting that they remembered the locations of simulated intruders. Male vireos approached playback sites of local songs, likely in their own repertoires, more precisely than foreign songs recorded 95–645 km from our study site. Songs included in local and foreign playback tapes differed primarily in frequency modulation, but were similar in other measurements. These results support ranging theory as described by Morton (1986). If the songs within an individual’s repertoire are ranged with greater accuracy, we discuss how the stability of neighborhoods becomes a factor as to whether or not selection will favor repertoire sharing in song evolution. As well, singing style is affected by ranging. Because Blue-headed Vireos present their songs in a stereotyped order, a listener can compare ordered sequential changes in signal degradation. Comparing degradation in a sequence of songs adds a temporal element that should result in more accurate ranging of the singer’s location. SINOPSIS. Determinaci ´ on de la distancia de cantos durante el periodo de incubaci´ on en Vireo solitarius: la importancia del repertorio de cantos y sus implicaciones en el patr´ on de exposici ´ on y poder discriminar entre cantos locales o dialectos Los mecanismos utilizados por las aves para determinar la distancia de canto de otros individuos est´ an siendo debatidos. La idea de que la canci´ on debe estar en el repertorio del recipiente para que sea arreglada con exactitud, es controversial, pero importante para poder entender la evoluci´ on del canto. Tratamos de probar la relaci´ on entre la tasa de exactitud y el repertorio de cantos utilizados. Para estos se exposo, a grabaciones de cantos, a individuos de Vireo solitarius cuya localizaci´ on se sab´ ıa con exactitud dado el caso de que dichos individuos estaban incubando. Los machos pudieron dar con la localizaci´ on del sonido y cuando los hembras los relevaron, volaron directamente hacia el lugar en donde se hab´ ıa puesto la grabaci´ on. Esto sugiere que recordaron la localidad desde donde se transmiti´ o el sonido. Los machos se acercaron a las grabaciones de canciones locales (que se encontraban en su propio repertorio), de forma m´ as precisa que las grabaciones de aves extra˜ nas o con otros dialectos. Si los cantos del repertorio de un individuo, son arreglados con gran exactitud, entonces la estabilidad de los cantos de los vecinos va ser un factor, no importa si la selecci´ on natural favorece un repertorio compartido, y es una fuente importante de selecci´ on en la evolucion del canto. Adem´ as, el estilo de canto puede ser afectado por su amplitud. El canto en el vireo estudiado es estereotipado y los que escuchan pueden comparar el orden secuencial de una se˜ nal degradada. El comparar la degradacion en la secuencia de un canto, a˜ nade un elemento temporal que debe producir como resultado el poder determinar con exactitud la localizacion de un ave que canta. Key words: singing style, song dialects, song familiarity, song neighborhood, spatial memory, territorial defense, Vireo solitarius 5 Current address: Hemlock Hill Field Station, 22318 Teepleville Flats Road, Cambridge Springs, Pennsylvania 16403, USA. Email: mortone@si.edu Birds have a remarkable ability for ranging (judging the direction and distance to) singing birds that they cannot see. A ranging bird de- termines a singer’s location by assessing both its compass direction and distance. Ranging C  2006 The Author(s). Journal compilation C  2006 Association of Field Ornithologists 291