Lateralization and motor stereotype of song production in the brown-headed cowbird

Song production in adult brown-headed cowbirds(Molothrus ater ater) is lateralized, with a slight right syringeal dominance. The left size of the syrinx produces low-frequency (200–2000 Hz) notes within the introductory note clusters, while the right side produces the higher-frequency (1500–6000 Hz) introductory notes, the interphrase unit (10–12 kHz), and the final high-frequency whistle (5–13 kHz). Cross-correlation analyses reveal that individual cowbirds produce each of their four to seven song types with a distinct stereotyped motor pattern–as judged by the patterns of syringeal airflow and subsyringeal pressure. The acoustic differences across song types are reflected in the differences in the bronchial airflow and air sac pressure patterns associated with song production. These motor differences are particularly striking within the second and third introductory note clusters where there is a rapid switching back and forth between the two sides of the syrinx in the production of notes. These motor skills may be especially important in producing behaviorally effective song. 1994 John Wiley & Sons, Inc.     

To trill or not to trill? Territorial response to a heterospecific vocal trait in male collared doves, Streptopelia decaocto

Responding of individuals outside the conspecific range hasbeen largely explained by biases in sensory or cognitive systemstoward particular traits or trait values. More recently, ithas been shown that such responses might occur if individualsstill respond to signal traits that have been lost over time.However, empirical evidence remains scarce. We report a casesupporting the latter mechanism. Phylogenetic analysis suggeststhat the collared dove, Streptopelia decaocto, had lost thetrilled vocalization present in most congeneric taxa. We testedwhether males retained the ability to respond to these trillsin the context of territory defense. We synthesized trilledsongs by inserting trills from the sister species S. roseogriseainto S. decaocto songs. We show that trilled songs yielded higherresponses than did natural conspecific songs, and that the intensityof the response depended on the number of trilled elements.We also show that trilled songs elicited as strong reactionsas frequency modulated coos, which are stronger releasers ofterritorial response than are nonmodulated coos, but are notproduced by every males. Additional tests suggest that the frequencypattern is the most important feature of the trill used by males.However, it is still unknown whether reactions to trilled andfrequency modulated coos have the same perceptual basis. Toour knowledge, this study is the first report of a stronglydeviating signal that is still effective in vocal intrasexualcommunication in birds.     

“Stripe” transcription factors provide accessibility to co-binding partners in mammalian genomes

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Different frequency control mechanisms and the exploitation of frequency space in passerines

1. Birdsong is used in reproductive context and, consequently, has been shaped by strong natural and sexual selection. The acoustic performance includes a multitude of acoustic and temporal characteristics that are thought to honestly reveal the quality of the singing individual.
2. One major song feature is frequency and its modulation. Sound frequency can be actively controlled, but the control mechanisms differ between different groups. Two described mechanisms are pressure‐driven frequency changes in suboscines and control by syringeal muscles in oscines.
3. To test to what degree these different control mechanisms enhance or limit the exploitation of frequency space by individual species and families, we compared the use of frequency space by tyrannid suboscines and emberizid/passerellid oscines.
4. We find that despite the different control mechanisms, the songs of species in both groups can contain broad frequency ranges and rapid and sustained frequency modulation (FM). The maximal values for these parameters are slightly higher in oscines.
5. Furthermore, the mean frequency range of song syllables is substantially larger in oscines than suboscines. Species within each family group collectively exploit equally broadly the available frequency space.
6. The narrower individual frequency ranges of suboscines likely indicate morphological specialization for particular frequencies, whereas muscular control of frequency facilitated broader exploitation of frequency space by individual oscine species.

     

White-throated sparrow morphs that differ in song production rate also differ in the anatomy of some song-related brain areas

White-throated sparrows are unusual among songbirds in that they occur in two color morphs, white-striped and tan-striped, determined by a chromosomal inversion and maintained by negative assortative mating. These differ in several reproductive behaviors, including amount of singing: white-striped males sing frequently, tan-striped females never sing, and tan-striped males and white-striped females sing an intermediate amount. The present study measures the volumes of several nuclei in the avian song system and relates these to color morph and to sex. We find that robustus archistristalis and the tracheosyringeal part of the hypoglossal nucleus, nuclei closely involved in song production, are larger in white-striped than in tan-striped birds. We also find morph differences for nuclei in the rostal division of the song system, nuclei believed to be less directly involved in song production. We find sex differences throughout the song system as has been reported in other songbirds. Relationships between structure and function in the song system are discussed. © 1995 John Wiley & Sons, Inc.