Sandra L. L. Gaunt

Song Learning as Evidenced from Song Sharing in Two Hummingbird Species (Colibri coruscans and C. thalassinus)

ABSTRACr.-We have demonstrated that male hummingbirds in the genus Colibri share song types. The Sparkling Violet-ear (C. coruscans) from an Ecuadorian population and Green Violetear (C. thalassinus) from populations in Costa Rica form aggregates or neighborhoods. Males of a neighborhood sing the same song type and those of distant neighborhoods have different song types. The resultant geographic variation in song, we suggest, is due to cultural drift acquired through song learning. Song sharing was determined not only by traditional, visual examination of spectrograms of song but with a relatively new, digital cross-correlation method that permits statistical treatment. The statistical procedures included cluster analysis that reflects the distribution of songs in geographic space and an evaluation for randomness of that distribution by use of the Mantel test. Received 13 May 1993, accepted 30 September 1993.

Syringeal Structure and Avian Phonation

Studies of syringeal function have historically been hampered by two difficulties, one technical and one perceptual. The technical difficulty is that because the syrinx is at the base of a long trachea and because its functioning is distorted if the surrounding interclavicular airsac is ruptured, direct observation of natural syringeal function has so far proved impossible. Hence, all analyses of syringeal function are based on indirect evidence. Such evidence may be obtained from dissections, manipulations of extracted syrinxes, models, analyses of physiological events associated with phonation, or analyses of the sounds produced.

DIGITAL SPECTROGRAPHIC CROSS-CORRELATION: TESTS OF SENSITIVITY

ABSTRACT Digital spectrographic cross-correlation (SPCC), a technique described by Clark et al. (1987), simultaneously analyses frequency, amplitude and time components of a signal, and returns a single peak correlation coefficient. The procedure is objective and uses all the information in the spectrogram. As such, it is a candidate to replace and/or supplement visual spectrogram comparison and multivariate analysis as the technique of choice for comparing sounds. With the increasing availability of sound analysis software with built-in cross-correlation routines, the procedure is becoming readily available to biologists who may not have extensive knowledge of acoustics. This ease of access increases the potential for misapplication of the technique or misinterpretation of results. To assess the utility of SPCC and to highlight pitfalls that need to be avoided in its implementation, we performed a series of tests designed to reveal the sensitivity of the peak cross-correlation coefficient to a variety of...

The effects of tracheal coiling on the vocalizations of cranes (Aves; Gruidae)

SummaryIt is generally supposed that the elongated, often coiled tracheae of many species of birds are adaptations for the production of loud, penetrating calls. A corollary supposition is that the acoustic effects are produced by the resonant properties of the elongated tube, with the birds being analogized to a wind instrument. We have experimented with several species of cranes possessing different degrees of tracheal coiling. Regardless of the degree of coiling, all cranes can utter extremely loud calls using remarkably low driving pressures. Neither surgical modifications of the trachea nor changing the respiratory gases to helium-oxygen produced consistent changes of voice that could be unambiguously attributed to changes of tubal resonances. However, shortening the trachea markedly reduced vocal intensity, the degree of reduction being roughly proportional to the degree of shortening. Although some of that reduction may derive from an increased impedance mismatch at the external aperture of the tube, and some from a decreased radiation directly from the hard walls of the trachea, these explanations scarcely account for the dramatic effects we observed. We, therefore, hypothesize a more unusual mechanism: The tracheal coils that are embedded in the sternum serve a function analogous to the bridge of a stringed instrument, transmitting the vibrations of a tiny sound source to a large radiating surface, the sternum. The sternum then vibrates against the large internal air reservoir of the avian airsac system. As it has a complex shape, the sternum will have many resonances and will respond to many frequencies; as a solid oscillator, its resonances will not be greatly affected by low density gases. Hence, we suggest that cranes and other birds with enlarged windpipes are more properly analogized with a violin than a trombone.

MECHANICS OF THE SYRINX IN GALLUS GALLUS. I. A COMPARISON OF PRESSURE EVENTS IN CHICKENS TO THOSE IN OSCINES

Oscines generally (always?) have an EL, while non-passerines generally lack it. It is certainly absent from chickens, and the labia associated with the bullae of some male anatids show a quite different structure. The syrinx of chickens also differs from that of ostines in the nature and position of the vibrating membranes. A chicken’s syrinx is tracheobronchial (fig. 1). Just anterior to the syrinx the final four rings of the trachea are fused into a “drum.” The pessulus is a dorsoventrally-oriented, cartilaginous bar in the medial plane marking the divergence of the brouchi from the trachea. The ends of this bar are expanded into triangular plates at the dorsal and ventral surfaces, giving it a dumbbell-like appearance. Between the posterior end of the drum and the pessulus, the trachea is strongly laterally compressed. Its walls are essentially membranous, comprising the external tympaniform membranes, the anterior portions of which are invested by cartilaginous partial rings. Hence, the external tympaniform membranes are directly opposed to each other in this region. They continue posteriad onto the bronchi where they are also opposed by the internal tympaniform membranes. Experiments by Gross (196413) indicated that the external tympaniform membranes are the major source of sound production in chickens. In contrast, the sound-producing mem

Respiratory responses to acute heat stress in cranes (Gruidae): the effects of tracheal coiling

Some species of cranes have extensive coiling of their trachea that substantially increases their anatomical dead space. We subjected individuals of four species of cranes (Anthropoides virgo, Balearica regulorum, Grus grus and Grus japonensis) to acute heat stress to investigate the effectiveness of this trait as a thermoregulatory adaptation. We measured cloacal temperature, respiratory flow and frequency and arterial pH during normothermic breathing and thermal panting. Extra tracheal length appears to be a helpful but nonessential adaptation to prevent cranes from becoming alkalotic while panting. Cranes in our study had relatively lower panting frequencies and greater tidal volumes than have been reported for other birds subjected to heat stress. Tracheal coiling is probably more important to vocalization than to respiration or thermoregulation.

COMMUNITY ASSEMBLY PATTERNS OF PARIDS ALONG AN ELEVATIONAL GRADIENT IN WESTERN CHINA

Abstract Eight species of parids commonly occur in the mountains of northern Sichuan Province, Peoples Republic of China. They represent four monophyletic groups regarded by some authorities as genera, but more traditionally as subgenera of the large genus Parus. To test the competition-based hypothesis that less closely related species are more likely to co-occur, we used specimens and observations obtained in October 1989 and May 1991 to delineate the morphology, elevational range, and habitat associations of each species in this rich assemblage. A morphometric cluster analysis did not support the assumption that phylogenetic similarity predicts morphological and hence ecological similarity. Up to five species commonly co-occurred in mixed flocks, as in Europe (where five subgenera are represented), but a randomization test showed that community assembly was random with respect to subgenus. On the other hand, for the entire data set (P = 0.05) and during spring (P = 0.07), species in the same morphometric cluster were less likely to co-occur than were species with dissimilar morphology. It appears, therefore, that competition between species of similar morphology may play (or have played) some role in structuring assemblages of parids during the breeding season in this area. For this reason, more detailed studies of the parid assemblage in this area are recommended.

Database design for an archive of animal sounds

Attached to several museums worldwide are sound archives, units dedicated to collecting, preserving, and making available to others recordings of animal sounds. In the case of the Borror Laboratory of Bioacoustics (BLB) at The Ohio State University, most recordings in the archive are the products of research by staff and students. The users of the collection include scientists, governmental agencies, and commercial enterprises. In this article we describe our efforts to build a modern database that describes the sound recordings in our care at the BLB.

The digital archiving project at the Borror Laboratory of Bioacoustics

The Borror Laboratory of Bioacoustics (BLB) at The Ohio State University is a research facility with an archive of recorded animal sounds collected primarily by BLB staff and associates. The 25 000 sound recordings are scientific data that require special treatment to ensure their longevity, and the BLB is, like other sound archives, dedicated to the preservation of these recorded sounds. Traditionally, sound recordings have been archived on analog 1/4‐in. magnetic tape. However, magnetic tape is degraded by time, usage, and excess temperature and humidity. Additionally, access to data on analog tapes is slow. Facing loss of access to data, especially on tapes exceeding their 50‐year life expectancy, we are copying the collection to digital format [compact disk recordable (CDR)] with the aid of funding from the National Science Foundation. Because digital technology has been tested and refined over nearly two decades, and CDR media for storage of digital data now sustains a viable commercial market, ar...

9 – Cognitive Processes in Avian Vocal Acquisition

Publisher Summary This chapter illustrates a comparative study of vocal acquisition by birds. It provides an insight into avian cognitive capacities in the realm of communication, i.e., memory, information processing, and categorization. Variation exists within and between avian taxa in the representation of sound information in memory, i.e., cognitive content, and when those memories are obtained, processed, and organized, i.e., cognitive structure-function. Recognition of this variation can aid in elucidating the development and evolution of avian vocal communication systems. The cognitive functions of selective attention, information processing, decision processing, and choice between alternative strategies channelize behavioral responses to a range of environmental stimuli such as food types, temperatures, etc. In vocal communication, the animal must attend to, select from, and/or respond to sounds that may range from noninformative background noise to information-rich and species-typical signal(s). Thus, animals must have mechanisms that facilitate the recognition of appropriate signals at one level, and decision processes concerning response to and/or production of signals at another. Signal recognition as well as vocal expression may be directed wholly or in part by pre-existing, heritable representations within the nervous system. Even such nonconscious and/or stereotypic signals and signaling responses, however, can be influenced by cognitive processes.