Condor, Volume 108(2), May 2006
THE DUET CODE OF THE FEMALE BLACK-BELLIED WREN Logue, David M. SINGING OF HERMIT WARBLERS: DIALECTS OF TYPE I SONGS Janes, Stewart W.; Ryker, Lee Abstracts: THE DUET CODE OF THE FEMALE BLACK-BELLIED WREN Logue, David M. In many duet-singing songbirds, paired birds combine their song types nonrandomly to form duet songs. Several different behavioral mechanisms could generate nonrandom song type associations in duets. I tested female Black-bellied Wrens (Thryothorus fasciatoventris) for one such mechanism: adherence to a set of rules linking female response songs to male stimulus songs. I call this set of rules a "duet code." Duets of free-living Black-bellied Wrens were recorded in 2001 and 2002. In 2003 I returned to the same territories and played the male song types from the recorded duets. Females answered male song stimuli as if duetting with the playback speaker. Although the known repertoires of females averaged 8.4 song types, each female sang only a single song type in response to each male song type. Random answering could not account for this pattern, supporting the hypothesis that females abide by duet codes. Females that were still paired with their mates from 2001-2002 answered 100% of their mate's songs with the same song types they had used previously, demonstrating that codes are stable over time. In contrast, females that were new to a territory answered an average of only 18% of their mate's song types with the same song type as the previous female, indicating that duet codes are individually distinctive. Duet participation by female Black-bellied Wrens represents a special kind of animal communication, in which discrete vocal signals consistently elicit discrete vocal responses according to an individually distinctive set of rules. SINGING OF HERMIT WARBLERS: DIALECTS OF TYPE I SONGS Janes, Stewart W.; Ryker, Lee Hermit Warblers (Dendroica occidentalis) sing distinct dialects of type I songs, the most common song before pairing. Eight dialects were identified and described in a 22 900 km2 area in southwestern Oregon and northern California. The dialects were well defined geographically with contact areas between dialects seldom extending more than 6 km. Gaps in forested habitat of >= 10 km separated several dialects, but within forested areas dialect boundaries did not conform to obvious habitat, elevation, or geographic boundaries. Few songs containing syllables or phrases from more than one dialect were identified, and birds incorporating elements from two different dialects inhabited areas close to the common boundary between the two. Multivariate analysis showed that birds in neighboring areas had dialects most similar in structure, but a more complex history of dialect development or origin is suggested in other areas.
